NGS Status Report to GGOS Bureau for Networks and Communications
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Mike Pearlman (for Dru Smith)
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Dru Smith
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Kendall Fancher, Giovanni Sella
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2010/12/15
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San Francisco, CA
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GGOS Bureau for Networks and Communications
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IERS, GGOS, Co-location site surveys,Foundation CORS
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Download (pptx) (2.41 MB)
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Redefinition of the U.S. Vertical Datum: Replacing NAVD 88
Informational packet including GRAV-D updates
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Dru Smith
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Dru Smith
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2011/02/03
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Raleigh, NC
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NC Survey Summit
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GRAV-D, NAVD 88, NSRS, Vertical Datum
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Download (pptx) (6.40 MB)
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Terrestrial Gravity Plans at NGS
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Dru Smith
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Dru A Smith
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Mark Eckl, Vicki Childers
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2010/10/18
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TMGO / Longmont, CO
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North American Comparison of Absolute Gravimeters
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Gravity
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Download (pptx) (2.67 MB)
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An optimist's 20 year look-ahead at geodesy and geophysics
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Dru Smith
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Dru A Smith
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2010/05/17
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Washington, D.C.
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NRC Workshop on New Research Directions for NGA
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Geodesy, Future Trends
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Download (pptx) (2.86 MB)
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What is Geodesy?
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Dru Smith
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Dru Smith
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2009/05/20
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Online
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NOS Diving Deeper Podcast Series
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Geodesy, NGS
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Download (mp3) (32.01 MB)
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What is Geodesy? (short version)
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Dru Smith
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Dru A Smith
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2009/05/20
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Online
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NOS Diving Deeper Podcast Series
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Geodesy, NGS
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This is an edited/shortened version of the previous interview of the
same name.
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Download (mp3) (20.20 MB)
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GNSS Absolute Antenna Calibration at the National Geodetic Survey
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Andria Bilich
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Andria Bilich
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Gerald Mader, Charles Geoghegan
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2010/06/29
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Newcastle-on-Tyne, England
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IGS Workshop
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antenna calibration
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Download (pdf) (10.53 MB)
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GNSS Absolute Antenna Calibration at the National Geodetic Survey
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Andria Bilich
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Andria Bilich
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Gerald Mader
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2009/12/15
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San Francisco, CA
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AGU Fall Meeting
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antenna calibration
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Show Abstract
To meet the needs of the high-precision GNSS community, the
National Geodetic Survey (NGS) has constructed an absolute
antenna calibration facility which uses field measurements and
actual GNSS satellite signals to determine antenna phase center
patterns. A pan/tilt motor changes the orientation of the antenna
under test, and signals are received at a wide range of angles.
The phase center patterns will be publicly available and
disseminated in both the ANTEX and NGS formats. We provide the
observation models and strategy currently used to generate NGS
absolute calibrations, and propose some future refinements. We
also show examples of antenna calibrations from the NGS facility.
These examples are compared to the NGS relative calibrations as
well as absolute calibrations generated by other organizations.
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Download (pdf) (16.73 MB)
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The Impact of the Permanent Tide on GEOID96, G96SSS and NAVD 88
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Dru Smith
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Dru A Smith
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1997/05/28
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Baltimore, MD
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AGU
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Permanent Tide, Earth Tides, GEOID96, NAVD 88, G96SSS
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Show Abstract
The National Geodetic Survey has established a strategic goal of
developing the capability to obtain second-order, class II (FGCS
standards) orthometric heights using GPS combined with a high
resolution geoid model. As a contribution toward that goal, we
are working toward a 1 cm (1 sigma) geoid model for the
conterminous United States. Numerous signals effect the geoid at
and above the 1 cm level, and one of the most difficult to
properly implement has been the consideration of the permanent
tidal potential in geoid modeling. In creating G96SSS, it was
necessary to determine which tide system each of the following
data sets were referred to: terrestrial gravity measurements,
ship gravity measurements, altimetrically derived gravity
anomalies, digital terrain, and EGM96 coefficients. In some
cases, the question was difficult to answer. It was our intention
to produce G96SSS in the non-tidal system. From recent knowledge
of the parameters of the best fitting global ellipsoid, we know
that the G96SSS geoid contains undulations biased from the
non-tidal system by 12.0 cm. That is, undulations in the
non-tidal system may be obtained from the G96SSS model by
removing 12.0 cm from G96SSS. The tide system of GEOID96 was, by
definition, dependent on the tide system of the NAD 83 GPS
measurements, since GEOID96 was designed solely to convert
between NAD 83(86) GPS ellipsoid heights and NAVD 88 Helmert
orthometric heights. The GPS measurements were reduced to the
non-tidal system, so GEOID96 is also in that system. Finally, the
comparison between GPS heights on leveled benchmarks and G96SSS
yieled an estimate of the bias of NAVD 88 from global mean sea
level. In this comparison, it was essential to know the tide
systems of both GPS and G96SSS. With all data reduced to the
non-tidal system, our current best estimate of the NAVD 88 bias
is -31.4 cm, where the sense of the sign is that the NAVD 88 H=0
reference level is 31.4 cm below global mean sea level.
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Download (ppt) (0.15 MB)
|
GNSS Absolute Antenna Calibration at the National Geodetic Survey
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Andria Bilich
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Andria Bilich
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Gerald Mader
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2010/09/27
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Portland, OR
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ION GNSS
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antenna calibration, absolute calibration
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|
Download (pptx) (2.74 MB)
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Absolute Ionosphere Slant Delays From Ambiguous Carrier Phase Data
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Dru Smith
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Dru A Smith
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2005/01/25
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San Diego, CA
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ION NTM
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Ionosphere, CORS, TEC
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Show Abstract
NOAA’s National Geodetic Survey (NGS) has recently developed an
innovative new technique for computing the absolute slant delays
to GPS signals, caused by the ionosphere. This method relies
entirely on ambiguous carrier phase data, using both the orbital
geometry and the spacing of NOAA’s Continuously Operating
Reference Station (CORS) network of GPS receivers over the
Conterminous USA (CONUS) to solve for delays in absolute space.
Using this technique, a set of absolute slant delays between any
given CORS receiver and GPS satellite at any epoch can be
computed, and these delays then referred to GPS receivers
anywhere in CONUS using simple interpolation methods. This
eliminates the need for a grid of vertical delays, and all the
associated errors that accompany the mapping of vertical delays
into slant delays. This method was tested against a variety of
GPS positioning software and currently performs at the 1 TECU
(about 1 cycle on L1) level in absolute mode and at the 0.01 to
0.1 TECU level in double differenced mode. NGS plans to begin
computing daily models of the ionosphere slant delays in fall
2004 and releasing them as an experimental product under the name
ICON-1 (for Ionosphere over CONus, version 1). The data will be
made freely available for post processing and testing
applications. Future plans will be to increase the accuracy of
the modeling, reduce the latency of the models and formalize the
model as an official NOAA product.
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Download (ppt) (18.92 MB)
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Geodesy, Geodetic Control and Improving the NSRS
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Dru Smith
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Dru A Smith
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2010/05/21
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Federal News Radio
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Federal Drive Morning Show
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Geodesy, Geodetic Control, NSRS
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Show Abstract
National Geodetic Survey (NGS) Chief Geodesist, Dr. Dru Smith,
was interviewed on Federal News Radio 1500AM on Friday, May 21,
2010 following a press release that announced the conclusion of
an NGS-hosted Federal Geospatial Summit.
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Download (mp3) (1.89 MB)
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Applied Earth Science activities at NOAA's National Geodetic Survey
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Dru Smith
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Dru Smith
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2009/01/15
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Columbus, Ohio
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Ohio State University School of Earth Science
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Earth Science, NGS
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Download (ppt) (40.32 MB)
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PRELIMINARY ANALYSIS OF IGS REPROCESSED ORBIT & POLAR MOTION
ESTIMATES
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Jim Ray
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Jim Ray
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Jake Griffiths
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2009/04/20
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Vienna, Austria
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European Geoscience Union General Assembly
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IGS, GPS
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Show Abstract
Preliminary Analysis of IGS Reprocessed Orbit and Polar Motion
Estimates Jim Ray (Jim.Ray@noaa.gov) Jake Griffiths
(Jake.Griffiths@noaa.gov) The Analysis Centers (ACs) of the
International GNSS Service (IGS) are reanalyzing the history of
global network GPS data collected since 1994 in a consistent way
using the latest models and methodology. This is the first
reprocessing by the IGS, but it is expected to be repeated in the
future as further analysis and reference frame changes occur. All
eight final-product ACs are participating, together with three
other related groups. First partial results consisting of IGS
combined weekly SINEX TRF and EOP combinations have been
submitted to the IERS for ITRF2008. A snapshot of the available
AC weekly SINEX files was used covering the reprocessed years
2000 through 2007 plus the IGS regular operational solutions for
2008 (from week 1460 onward). Meanwhile, the full reprocessing
campaign will continue to completion by about the end of 2009 and
will cover the period 1994 to present with long-term consistent,
combined SINEX, orbit, and clock products. We have examined the
reprocessed AC orbit and polar motion (PM) estimates from the
1024 days (or 1025 for differences) of results till the end of
2007. These parameters are linked since PM is sensed in the GPS
modeling as a global diurnal sinusoidal motion of the terrestrial
frame relative to the satellite frame. Any similar type errors in
the orbital frame can bias the PM and PM rate estimates. For the
orbits, each daily AC satellite ephemeris for each pair of
consecutive days has been fit to the extended CODE orbit model,
extrapolated to the mid-point epoch between the days, and the
geocentric satellite position differences computed to give time
series of orbit repeatabilities. Occasional data gaps have been
filled by linear interpolation, FFT power spectra computed, and
the spectra stacked over the full GPS constellation and lightly
smoothed. Our analysis reveals considerable diversity among AC
orbits. Several show broad semi-annual (probably related mostly
to eclipsing) and fortnightly spectral peaks, as well as even
harmonics of the GPS draconitic year (1.040 cpy) with varying
amplitudes. High-frequency white noise floors can be detected in
most AC orbit spectra, with an average sigma of 14 mm and larger.
AC PM spectra mostly follow a power law with slope -4 for periods
shorter than about 20 d, as expected, except in the few cases
when ACs have applied tight day-to-day continuity constraints.
Indications of high-frequency white noise are seen in some AC
series. Day-boundary discontinuities computed using the AC PM
rate estimates can provide a sensitive probe of the quality of
the AC modeling, especially for the satellite orbit dynamics.
Like the orbit discontinuities, we find the PM discontinuities
vary greatly among the ACs. But most spectra of the PM
discontinuities show peaks at the annual (broad) and the O1 tidal
alias period of 14.19 d (narrow), in addition to odd (rather than
even) harmonics of 1.040 cpy. Previously both even and odd
harmonics of 1.040 cpy have been found in the spectra of station
position time series.
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Download (pdf) (0.34 MB)
|
FUTURE IMPROVEMENTS IN DETERMINATIONS OFEARTH ORIENTATION PARAMETERS
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Jim Ray
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Jim Ray
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2009/09/02
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Buenos Aires, Argentina
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International Association of Geodesy Scientific Assembly
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Earth orientation parameters, polar motion, Universal Time
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Show Abstract
FUTURE IMPROVEMENTS IN DETERMINATIONS OF EARTH ORIENTATION
PARAMETERS J.R. Ray NOAA, National Geodetic Survey, Silver
Spring, MD, USA The present accuracy of multi-technique combined
estimates for Earth orientation parameters (EOPs) can be assessed
using the ITRF2005 and other recent experience as a baseline.
Both components of polar motion (PM) have daily accuracies of
about 30 micro-as (about 1 mm equatorial rotation). GPS
observations dominate PM combinations owing to a strong global
tracking network and continuous data. VLBI and SLR are weaker due
to sparse, non-uniform networks so their PM rotational
information is largely exhausted to align their frames with GPS.
DORIS PM results are much noisier. GPS daily PM-rates are
accurate to about 150 micro-as per day but are subject to
prominent systematic errors related to orbit modeling and other
effects. Such errors are less obvious in the daily PM offsets.
UT1 accuracy is more difficult to evaluate because only VLBI is
able to observe it. (Nutation is similar and will not be
discussed here.) For VLBI networks designed to monitor EOPs, the
daily UT1 accuracy is usually between 4 and 10 micro-s (2 to 5 mm
equatorial rotation), though it is sometimes worse. Specialized
hour-long, single-baseline UT1 networks yield errors around 25 to
30 micro-s with major systematic errors. LOD measurements from
GPS have high-frequency errors of about 4 micro-s after modeling
time-varying biases by comparison with the best VLBI UT1 data.
Together, both can be combined to yield significantly improved
UT1/LOD estimates, though this is not yet done routinely by most
EOP services. Stronger future VLBI and SLR contributions will
depend largely on the deployment of more robust ground networks;
prospects are uncertain and recent trends are mixed. GPS PM is
unlikely to be improved much. But addition of data from new
GNSSs, with different orbital characteristics, might expose
presently undetected systematic errors. GPS LOD performance has
hardly changed for more than a decade. But, again, new GNSSs
could be important given the strong link with orbital dynamics.
At this time it is impossible to foresee how large any future
improvements might be. Interest is often expressed in subdaily
EOP variations but the main need now is for an updated
geophysical model for the diurnal and semidiurnal tidal bands.
Mitigation of network-dependent and other biases in the
hour-long, single-baseline VLBI UT1 data is also needed.
Detection of residual subdaily non-tidal PM variations (in the
sub-mm range) remains distant, but progress in monitoring
subdaily non-tidal UT1 will be a challenging possibility.
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Download (pdf) (1.02 MB)
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Upcoming replacements for NAD83, NAVD88 and IGLD85
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Dru Smith
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Dru Smith
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Richard Snay, Thomas Landon
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2009/05/12
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Toronto, Canada
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AGU / CGU
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NAD 83, IGLD 85, NAVD 88
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Show Abstract
The National Geodetic Survey (NGS), part of the National Oceanic
and Atmospheric Administration (NOAA) is responsible for
defining, maintaining and providing access to the National
Spatial Reference System (NSRS) for the United States. The NSRS
is the official system to which all civil federal mapping
agencies should refer, and contains, amongst other things, the
official vertical datum (NAVD 88), horizontal datum (NAD 83) and
great lakes datum (IGLD 85). Although part of the United States
NSRS, all three of these datums have been created through
international partnerships across North America. Unfortunately,
time has shown both the systematic errors existent within these
datums, as well as the inherent weaknesses of relying exclusively
on passive monuments to define and provide access to these
datums. In recognition of these issues, the National Geodetic
Survey has issued a “10 year plan�, available online, which
outlines steps which will be taken to update NAD 83, NAVD 88 and
IGLD 85 concurrently around the year 2018. The primary source of
success will be in the refinement of the CORS network and the
upcoming execution of the GRAV-D project (Gravity for the
Re-definition of the American Vertical Datum). Conversations are
ongoing with colleagues in Canada, Mexico, Central America and
the Caribbean in order to coordinate all of these efforts across
the entire continent. The largest changes expected to occur are
the removal of over 2 meters of non-geocentricity in NAD 83; the
removal of decimeters of bias and over a meter of tilt in NAVD
88; the addition of the ability to track motions (subsidence,
tectonics, etc) in the datums; the removal of leveling as a tool
for long-line height differencing; the use of a “best� geoid as
the orthometric height reference surface; the addition of datum
velocities (motions of the geometric frame origin and motions of
the geoid); and the use of GNSS technology as the way to access
both orthometric and dynamic heights in the vertical datum. This
talk will outline the broad plan of action and invite further
collaboration along these lines.
|
Download (ppt) (11.79 MB)
|
STATUS & PROSPECTS FOR IGS POLAR MOTION MEASUREMENTS
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Jim Ray
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Jim Ray
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Rémi Ferland
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2009/10/19
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Warsaw, Poland
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IERS Workshop on EOP Combination & Prediction
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polar motion, IGS, GNSS
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Show Abstract
Status and Prospects for IGS Polar Motion Measurements Jim Ray
(1), Remi Ferland (2) (1) U.S. NOAA/National Geodetic Survey, USA
(2) Geodetic Survey Division, NRCan, Canada GNSS-based
measurements of polar motion by the International GNSS Service
(IGS) dominate modern multi-technique combinations. This can be
attributed to a very strong global tracking network and
continuous data. IGS Final polar motion coordinates have daily
accuracies of about 30 micro-as (about 1 mm of equatorial
rotation), or perhaps a bit better for the most recent results.
The daily polar motion rate measurements have larger errors,
about 160 micro-as/day, largely due to greater sensitivity to
errors in the IERS model for subdaily EOP tidal variations. Orbit
modeling errors also affect the polar motion rates and perhaps
also the polar motion offsets at a subtle level. IGS Ultra-rapid
products provide reduced latency and more frequent updates with
only modestly increased errors.
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Download (pdf) (0.52 MB)
|
Recent IERS Site Survey of Multiple Co-located Geodetic Techniques by
NGS
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Dru Smith
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Kendall Fancher
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Dru Smith, Steve Breidenbach, Jeff Olsen, Nagendra Paudel
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2010/04/14
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Sydney, Australia
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FIG
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IERS, Co-location site surveys
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Show Abstract
The National Geodetic Survey (NGS) of the United States, in
collaboration with the National Aeronautics and Space
Administration (NASA) and the International Earth Rotation
Service (IERS), recently conducted a site survey of four space
geodesy techniques: Satellite Laser Ranging (SLR), Very Long
Baseline Interferometry (VLBI), Doppler Orbitography and
Radio-positioning Integrated by Satellite instrument (DORIS), and
the Global Positioning System (GPS), collocated at the Goddard
Geophysical and Astronomic Observatory (GGAO) in Greenbelt, MD.
This survey sought to determine, at the highest levels of
accuracy, the geometric vectors which connect multiple geodetic
techniques at a terrestrial site where these techniques are
located near to one another. Realization of the International
Terrestrial Reference Frame (ITRF) is enhanced by combining and
comparing different space geodetic techniques through local ties
referred to as site surveys. Because these four techniques all
contribute their own strengths to the determination of the ITRF,
the quality of the connectivity between the techniques is a
direct contributor to the accuracy of the ITRF itself. Site
surveys of the GGAO space geodesy techniques have been carried
out periodically in the past. The site survey carried out by the
NGS allowed for an independent comparison against results from
previously conducted site surveys. The ultimate goal of this site
survey was to improve the overall accuracy of local ties between
space geodesy techniques by employing the latest surveying
technology, as well as re-engage NGS in the field of IERS site
surveys. Results of the survey will be presented, as well as
discussion of future surveys and possible collaborations with
other international surveying teams to improve the overall
connectivity of techniques used in defining the ITRF.
|
Download (pptx) (1.61 MB)
|
Status & Prospects for Combined GPS LOD & VLBI UT1
Measurements
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Ken Senior
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Ken Senior
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Jan Kouba & Jim Ray
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2009/10/19
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Warsaw, Poland
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IERS Workshop on EOP Combination & Prediction
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Universal Time, UT1, length of day, LOD, VLBI, IGS, GPS
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Show Abstract
Status and Prospects for Combined GPS LOD and VLBI UT1
Measurements Ken Senior (1), Jan Kouba (2), Jim Ray (3) (1) U.S.
Naval Research Laboratory, USA (2) Geodetic Survey Division,
NRCan, Canada (3) U.S. NOAA/National Geodetic Survey, USA Our
Kalman filter combines irregular VLBI UT1-UTC with daily GPS LOD
by handling correlated GPS errors with a Gauss-Markov plus
fortnightly sinusoid model added to the random walk excitation.
Evaluated against (AAM + OAM), this filter gives the lowest
residuals and highest correlations. Optimal UT1+LOD results
exclude UT1 from all Intensives plus other VLBI sessions with
formal errors >5 microsec. Rescaling VLBI formal errors is not
fully effective for the heterogeneous VLBI data. GPS LOD esimates
are more uniform, but biased; but properly modeled, the LOD
residuals are ~4 microsec. Addition of GPS LOD significantly
improves combined UT1 series. Prediction services could benefit
further using the IGS Ultra-rapid LOD values reported four times
daily with 15 hr delay.
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Download (pdf) (2.38 MB)
|
Preparations for the 2nd IGS Reprocessing Campaign
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Jim Ray
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Jim Ray
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2009/12/14
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San Francisco, CA
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American Geophysical Union Fall Meeting
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IGS, GPS, data analysis, geophysical models
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Show Abstract
Preparations for the 2nd IGS Reprocessing Campaign Jim Ray The
Analysis Centers (ACs) of the International GNSS Service (IGS)
are now completing their first collective reanalysis of the
history of global network GPS data collected since 1994. A
consistent set of the latest models and methodology is being used
to generate GPS orbits, Earth orientation parameters (EOPs),
station coordinate time series, and station and satellite clocks.
These results have been contributed to the new ITRF2008
multi-technique terrestrial reference frame and EOP combination.
Preparations will begin during 2010 for the next IGS reprocessing
effort. Despite the major progress made in the first IGS
reanalysis, further analysis improvements remain to be
implemented. The list includes: add GLONASS as well as GPS
observations; adopt a new reference frame based on ITRF2008;
update the IGS antenna calibrations based on the first
reprocessing results and other sources; use the new EGM2008
geopotential model with perhaps revised time-varying
coefficients; implement a model for previously neglected
higher-order ionospheric effects; consider the satellite
dynamical effects of Earth albedo reflection and re-radiated
thermal emissions; apply various refinements in modeling
tropospheric delays; include station displacements due the S1 and
S2 atmospheric pressure tides; use a new model for the subdaily
EOP tidal variations, if available; reconsider the handling of
EOP constraints and a prioris by ACs; incorporate all high-order
relativistic effects; and revisit the treatment of all analysis
constraints to remove as many as possible and to understand
better the effects of those that remain. Other operational
aspects need to be evaluated also, such as how best to treat
non-tidal loading station displacements, whether to continue
forming weekly SINEX solutions or to move instead to daily
integrations, and more consistent and rigorous methods to combine
AC solutions.
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Download (pdf) (0.05 MB)
|
Results from the New IGS Time Scale Algorithm
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K. Senior
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K. Senior
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Jim Ray
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2009/12/14
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San Francisco, CA
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American Geophysical Union Fall Meeting
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time scales, clocks, IGS
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Show Abstract
Results from the New IGS Time Scale Algorithm (version 2.0) Ken
Senior (1), Jim Ray (2) (1) U.S. Naval Research Laboratory, USA
(2) Geodetic Survey Division, NRCan, Canada Since 2004 the IGS
Rapid and Final clock products have been aligned to a highly
stable time scale derived from a weighted ensemble of clocks in
the IGS network. The time scale is driven mostly by Hydrogen
Maser ground clocks though the GPS satellite clocks also carry
non-negligible weight, resulting in a time scale having a one-day
frequency stability of about 1E-15. However, because of the
relatively simple weighting scheme used in the time scale
algorithm and because the scale is aligned to UTC by steering it
to GPS Time the resulting stability beyond several days suffers.
The authors present results of a new 2.0 version of the IGS time
scale highlighting the improvements to the algorithm, new
modeling considerations, as well as improved time scale
stability.
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Download (ppt) (1.07 MB)
|
STATUS OF IGS CORE PRODUCTS
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Jim Ray
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Jim Ray
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Jake Griffiths
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2010/06/28
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Newcastle Upon Tyne, UK
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IGS Workshop 2010
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IGS, orbits, EOPs, GNSS
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Show Abstract
STATUS OF IGS CORE PRODUCTS The core products of the IGS consist
of global terrestrial frames, GNSS orbits, Earth rotation
parameters (ERPs), and clocks. Three main product series are
issued with varying latency, accuracy, and completeness:
Ultra-rapids (predictions and observations) for real-time and
near real-time applications; later Rapids for near-definitive
results; and still later Finals for the most complete and
accurate uses. The accuracies of all IGS products are heavily
dominated by systematic errors. Beginning with the orbits,
rotational errors greatly exceed random noise probably due to
limitations of current once-per-rev empirical parameterizations
and errors in the IERS subdaily tidal ERP model. These error
components alias into longer-period effects, including draconitic
harmonics, and then propagate into all other products. Having
said that, however, it is nevertheless true that the accuracy and
utility of IGS GNSS products exceed that of any other sources,
usually by large amounts, for all but a handful of observables,
UT1 and the terrestrial frame scale being probably the most
notable exceptions. The overall IGS quality has steadily improved
over time, though we are probably near an asymptotic level now. A
key responsibility of the IGS must be to identify the residual
error sources in its products, develop methods to mitigate them,
and advise users how best to avoid misinterpretation of spurious
effects. This becomes an ever more challenging task as both the
product generation and usage progressively move toward fully
automated and routine operations. The current status of IGS
products will be reviewed and suggestions offered for some
operational changes.
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Download (pdf) (1.91 MB)
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DEPENDENCE OF IGS PRODUCTS ON THE ITRF DATUM
|
Jim Ray
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Jim Ray
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Paul Rebischung & Ralf Schmid
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2010/10/04
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Marne-la-Vallee, France
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International Association of Geodesy REFAG 2010 Symposium
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reference frames, IGS, GNSS, datum
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Show Abstract
Dependence of IGS Products on the ITRF Datum J. Ray (1) P.
Rebischung (2) R. Schmid (3) (1) NOAA/National Geodetic Survey,
USA (2) Institut Geographique National, France (3) Technische
Universitaet Muenchen, Germany Throughout its history of nearly
two decades, the International GNSS Service (IGS) has attempted
to align its products as closely as possible to the successive
realizations of the International Terrestrial Reference Frame
(ITRF). This has been disruptive for IGS users at times,
especially during the 1990s when some radial ITRF datum
definitions were adopted. During the past decade IGS impacts due
to ITRF updates have been smaller and mostly been caused by
random and systematic errors in the results from the contributing
space geodetic techniques. As with all techniques, frame
rotational orientations are purely conventional and so the IGS
relies on the ITRF via a subset of reliable, globally distributed
stations with no significant problems. As regards the origin, the
IGS in principle could be self-reliant, or contributory, in
determining a frame origin aligned to the long-term center of
mass of the entire Earth system. In practice, however, GNSS-based
results have been less reliable than those from satellite laser
ranging (SLR) to LAGEOS. So the ITRF origin, based on SLR only,
has been adopted historically. Until the transition from ITRF2005
to ITRF2008 there have sometimes been significant shifts
associated with this practice as SLR results have evolved.
However, the present stability of the ITRF origin may finally
have reached the ~1 mm level, though that remains to be verified.
In many respects, the IGS dependence on the ITRF scale is most
subtle and problematic. In addition to an overall Helmert
alignment of the IGS frame to match the ITRF scale (and other
datum parameters), since 2006 the IGS calibration values for the
GNSS satellite antenna z-offsets depend directly on the same ITRF
scale (due to high correlations if the IGS frame scale is not
fixed). We therefore face a non-linear situation to maintain full
consistency between all IGS products and the ITRF scale: each IGS
frame contribution to ITRF based on one set of antenna
calibrations must be used, together with frames from other
techniques, to determine an updated ITRF and new antenna
calibrations, which are then no longer strictly consistent with
the starting IGS frame. One can hope that the process will
iteratively converge to a sufficient accuracy eventually. But
potentially large shifts in the ITRF scale, such as the -0.94 ppb
(about -6 mm in height) change from ITRF2005 to ITRF2008, are
highly disruptive, much more so than the associated rotational or
translational shifts. Only SLR and very long baseline
interferometry (VLBI) have been considered reliable and accurate
enough to be used for the ITRF scale. But experience and
theoretical studies have shown that neither is accurate to better
than about 1 ppb. Note in particular that the formal 2 ppb error
of GM (which should probably be closer to 1 ppb based on recent
results) fundamentally limits the possible SLR/VLBI scale
agreement to no better. Consequently, the IGS strongly urges that
the ITRF scale hereafter be fixed conventionally to the ITRF2008
scale indefinitely in the future until it is convincingly shown
that VLBI and/or SLR can determine the ITRF scale within 0.5 ppb.
If this is not done, the IGS may maintain its own frame aligned
to the ITRF2008 scale in order to minimize operational
disruptions.
|
Download (pdf) (1.41 MB)
|
CURRENT POSITIONING ACCURACY USING SPACE GEODESY
|
Jim Ray
|
Jim Ray
|
|
2010/12/13
|
San Francisco, CA
|
American Geophysical Union Fall Meeting
|
space geodesy, GPS, GNSS, IGS, accuracy, orbits
|
Show Abstract
Current Accuracy of Terrestrial Positions from Space Geodesy In
the International System (SI) of units, length is specified in
terms of a corresponding time interval via an adopted value for
the speed of light. Moreover, the SI second can be realized more
accurately than any other base unit. So, since all space geodetic
positioning systems rely inherently on high-accuracy timing
measurements, one might suppose that position determinations can
be traced directly and accurately to the SI meter. In fact, such
metrological assessments are very limited. This is mainly because
it is not practical to materialize metrological standards over
distances longer than about 1 km, for which the best GPS
accuracies demonstrated have been about 0.3 mm RMS. Relating such
highly localized accuracies to global measurements is extremely
problematic, however, for many reasons. Generally, errors
unrelated to thermal measurement noise processes grow rapidly as
the spatial scale increases and quickly dominate. The classical
metrics most often used as a substitute for true global geodetic
accuracy are: 1) repeatability of a given parametric estimate to
gauge internal precision; and 2) differences among independent
techniques to estimate external relative accuracy. Clearly,
repeatability can only set a lower limit to true absolute
accuracy since systematic biases are normally undetectable by
this method. External comparisons, even when feasible, may be
skewed unfavorably if it is necessary to use intermediate
measurements, which have their own errors (such as local ties to
relate station coordinates among co-located observing systems).
When direct external comparisons are possible (such as for polar
motion), the results can be optimistic if systematic errors are
not genuinely independent (such as relying on common data
reduction and geophysical models). When one system is clearly
superior to any others, it is especially difficult to estimate
its accuracy in any reliable absolute sense. Despite the
difficulties involved, accuracy assessments can be useful to
guide technique improvements by identifying limiting errors and
spurring efforts to better control them. This paper will review
current accuracy estimates for some space geodetic positioning
measures.
|
Download (pdf) (0.63 MB)
|
Using the Vermont CORS Network to Access the National Spatial
Reference System
|
Dan Martin
|
Dan Martin
|
|
2011/01/26
|
Vermont (Webinar)
|
Vermont Center for Geographic Information / Vermont Spatial Data
Partnership
|
Vermont, CORS, NSRS, RTN
|
Show Abstract
Using the Vermont CORS Network to Access the National Spatial
Reference System In 2006, the Vermont Agency of Transportation
began to install a network of Continuously Operating GNSS
Reference Stations (CORS). Now, nearly four and a half years
later the network is almost complete. The use of the VT network
by positioning professionals has been steadily increasing, and it
is anticipated that its use will begin to grow exponentially over
the next couple of years. Topics covered in this webinar will
include: • A brief description of the VT CORS network and how it
fits into the National CORS Network • Current capabilities and
usage of the network • A description of current methods and
techniques of accessing the NSRS using the VT CORS • Future
trends for accessing the NSRS
|
Download (pptx) (5.71 MB)
|
New Developments for OPUS
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
|
2011/03/04
|
Arvada, CO, USA
|
1ST ANNUAL ROCKY MOUNTAIN SURVEYORS SUMMIT
|
OPUS
|
Show Abstract
The On-line Positioning User Service (OPUS) is a National
Geodetic Survey tool that provides you with a National Spatial
Reference System coordinate via email in seconds using your own
GPS data file. The OPUS BETA website offers several notable
enhancements. OPUS-Projects is a new option providing tools to
handle GPS projects involving several sites occupied over several
days. OPUS-Projects includes project visualization and management
tools, enhanced processing options, and “one click� publishing
for an entire project. OPUS-S uses a new processing strategy. By
including more CORS at various distances and more sophisticated
geophysical models, this new strategy improves the reliability of
the results without sacrificing flexibility. OPUS-RS also offers
a new CORS selection strategy which improves reliability and
expands the regions in which this is a viable processing option.
Underlying these enhancements are new CORS coordinates derived
from a recently completed global GNSS network solution. This
solution provides improved coordinates for all included CORS that
are consistent with recognized reference systems such as the
ITRF2008. These and other new developments will be described.
|
Download (pptx) (13.85 MB)
|
New Developments for OPUS
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
|
2011/02/25
|
Morgantown, WV, USA
|
West Virginia Society of Professional Surveyors 43rd Annual
Convention
|
OPUS
|
Show Abstract
The On-line Positioning User Service (OPUS) is a National
Geodetic Survey tool that provides you with a National Spatial
Reference System coordinate via email in seconds using your own
GPS data file. The OPUS BETA website offers several notable
enhancements. OPUS-Projects is a new option providing tools to
handle GPS projects involving several sites occupied over several
days. OPUS-Projects includes project visualization and management
tools, enhanced processing options, and “one click� publishing
for an entire project. OPUS-S uses a new processing strategy. By
including more CORS at various distances and more sophisticated
geophysical models, this new strategy improves the reliability of
the results without sacrificing flexibility. OPUS-RS also offers
a new CORS selection strategy which improves reliability and
expands the regions in which this is a viable processing option.
Underlying these enhancements are new CORS coordinates derived
from a recently completed global GNSS network solution. This
solution provides improved coordinates for all included CORS that
are consistent with recognized reference systems such as the
ITRF2008. These and other new developments will be described.
|
Download (pptx) (13.84 MB)
|
New Developments for OPUS
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
|
2011/02/02
|
Morgantown, WV, USA
|
New Jersey Society of Professional Land Surveyors Surcon 2011
|
OPUS
|
Show Abstract
The On-line Positioning User Service (OPUS) is a National
Geodetic Survey tool that provides you with a National Spatial
Reference System coordinate via email in seconds using your own
GPS data file. The OPUS BETA website offers several notable
enhancements. OPUS-Projects is a new option providing tools to
handle GPS projects involving several sites occupied over several
days. OPUS-Projects includes project visualization and management
tools, enhanced processing options, and “one click� publishing
for an entire project. OPUS-S uses a new processing strategy. By
including more CORS at various distances and more sophisticated
geophysical models, this new strategy improves the reliability of
the results without sacrificing flexibility. OPUS-RS also offers
a new CORS selection strategy which improves reliability and
expands the regions in which this is a viable processing option.
Underlying these enhancements are new CORS coordinates derived
from a recently completed global GNSS network solution. This
solution provides improved coordinates for all included CORS that
are consistent with recognized reference systems such as the
ITRF2008. These and other new developments will be described.
|
Download (pptx) (13.82 MB)
|
New Developments for OPUS
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
|
2010/07/22
|
Virginia Beach, VA, USA
|
Virginia Association of Surveyors 2010 Conference
|
OPUS
|
Show Abstract
The On-line Positioning User Service (OPUS) is a National
Geodetic Survey tool that provides you with a National Spatial
Reference System coordinate via email in seconds using your own
GPS data file. Several notable enhancements are pending or in
development. OPUS-Projects is a new option providing tools to
handle GPS projects involving several sites occupied over several
days. OPUS-Projects includes project visualization and management
tools, enhanced processing options, and “one click� publishing
for an entire project. OPUS-S uses a new processing strategy. By
including more CORS at various distances and more sophisticated
geophysical models, this new strategy improves the reliability of
the results without sacrificing flexibility. OPUS-RS also offers
a new CORS selection strategy which improves reliability and
expands the regions in which this is a viable processing option.
Underlying these enhancements are new CORS coordinates derived
from a recently completed global GNSS network solution. This
solution provides improved coordinates for all included CORS that
are consistent with recognized reference systems such as the
ITRF2000. These and other new developments will be described.
|
Download (pptx) (17.07 MB)
|
New Developments for OPUS
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
|
2010/04/15
|
Baltimore, MD, USA
|
Maryland Society of Surveyors 2010 Conference
|
OPUS
|
Show Abstract
The On-line Positioning User Service (OPUS) is a National
Geodetic Survey tool that provides you with a National Spatial
Reference System coordinate via email in seconds using your own
GPS data file. Several notable enhancements are pending or in
development. OPUS-Projects is a new option providing tools to
handle GPS projects involving several sites occupied over several
days. OPUS-Projects includes project visualization and management
tools, enhanced processing options, and “one click� publishing
for an entire project. OPUS-S uses a new processing strategy. By
including more CORS at various distances and more sophisticated
geophysical models, this new strategy improves the reliability of
the results without sacrificing flexibility. OPUS-RS also offers
a new CORS selection strategy which improves reliability and
expands the regions in which this is a viable processing option.
Underlying these enhancements are new CORS coordinates derived
from a recently completed global GNSS network solution. This
solution provides improved coordinates for all included CORS that
are consistent with recognized reference systems such as the
ITRF2000. These and other new developments will be described.
|
Download (pptx) (17.02 MB)
|
New Coordinates for CORS Sites
|
Giovanni Sella
|
Giovanni Sella
|
Jake.Griffiths@noaa.gov
|
2011/03/08
|
Silver Spring
|
Webinar Open to All
|
CORS coordinates NAD83
|
Show Abstract
This webinar focused on describing the forthcoming change in
coordinates (position and velocities) for CORS sites from
ITRF2000 epoch 1997.0 and NAD 83(CORS96)epoch 2002.0. The new
coordinates will be available in NGSTRF08 epoch 2005.0 and NAD
83(2011) epoch 2010.0. The underlying datum for IGS08 is based on
ITRF2008, but the positions are calibrated for the impending
release of IGS08 (+igs08.atx). In this webinar, we will describe
the: - methodology used to establish the new coordinates -
magnitude of the coordinate changes - implications for
post-processing applications outside of NGS.e.g. holding CORS
with fixed positions and use of absolute (vs. relative) antenna
calibrations - time-frame for the distribution of coordinates
|
Download (pdf) (7.04 MB)
|
NGS' National height Modernization Program
|
Renee Shields
|
Renee Shields
|
Dan Roman, Vicki Childers
|
2011/02/21
|
Anchorage, AK
|
45th Alaska Surveying and Mapping Conference
|
Height Modernization, GRAV-D, Heights, geoid model
|
Show Abstract
The mission of NOAA's National Geodetic Survey is to define,
maintain and provide access to the National Spatial Reference
System (NSRS), including vertical control for measuring accurate
elevations. Since 2000, NGS has been implementing an initiative
to improve access to the vertical component of the NSRS through
technologies like Global Navigation Satellite Systems (GNSS). The
program has been implemented through a state-by-state approach
funded by Congressional earmarks, but in 2006 NGS began a more
comprehensive approach to ensure consistency across the nation
was achieved. NGS also began investigating a new approach to
defining the vertical datum through a high accuracy gravimetric
geoid. Details can be found in the project plan, Gravity for the
Re-definition of the American Vertical Datum (GRAV-D), and in the
NGS 10-year plan. This workshop will describe how each of these
programs have a role to play in improving the vertical reference
frame of the United States.
|
Download (ppt) (38.91 MB)
|
Results from the New IGS Time Scale Algorithm
|
K. Senior
|
K. Senior
|
J. Ray
|
2010/06/30
|
Newcastle Upon Tyne, UK
|
IGS Workshop 2010
|
time scales, clocks, IGS
|
Show Abstract
Results from the New IGS Time Scale Algorithm Since 2004 the IGS
Rapid and Final clock products have been aligned to a highly
stable time scale derived from a weighted ensemble of clocks in
the IGS network [Senior et al., 2003]. The time scale is driven
mostly by Hydrogen Maser ground clocks though the GPS satellite
clocks also carry non-negligible weight, resulting in a time
scale having a one-day frequency stability of about 1E-15.
However, because of the relatively simple weighting scheme used
in the legacy time scale algorithm and because the scale is
aligned to UTC by steering it to GPS Time the resulting stability
over shorter intervals and beyond several days suffers. A new
time scale algorithm (version 2.0) has been implemented to
address these limitations. The algorithm has been evaluated to a
subset of data in the IGS REPRO1 reprocessing campaign, presented
here. Repro1 products are currently being re-aligned using this
new timescale algorithm.
|
Download (ppt) (1.06 MB)
|
Status Report on the National Geodetic Survey's 10-Year Plan
|
Daniel R. Roman, Ph.D.
|
Daniel R. Roman, Ph.D.
|
|
2010/04/27
|
PHoenix, Arizona
|
American Congress of Suveying and Mapping
|
NGS Ten Year Plan
|
Show Abstract
This program discusses the foundational elements of the National
Spatial Reference System (NSRS), including: Fundamental geodetic
concepts of horizontal and vertical datums such as NAD 83 and
NAVD 88; reference ellipsoids and geoid models. Discussions will
include the realization of the datums in the form of GPS High
Accuracy Reference Networks (HARNs) and the international
densification of the Continuously Operating Reference Stations
(CORS) network and their impact on the design and implementation
of local geodetic systems, release of a new national geoid model,
enhancements to the On-Line Positioning User Service (OPUS) suite
of programs, and the major elements of the NGS ten-year plan for
modernization of NSRS.
|
Download (ppt) (18.04 MB)
|
Interpretations of Complete Bouguer Gravity Anomalies from the GRAV-D
Project in Alaska
|
Theresa M. Diehl
|
Theresa M. Diehl
|
Sandra Preaux and Vicki Childers
|
2010/12/14
|
San Francisco, CA
|
American Geophysical Union Annual Meeting
|
Airborne gravity, GRAV-D, geodesy, tectonics, Alaska
|
Show Abstract
The GRAV-D (Gravity for the Redefinition of the American Vertical
Datum) Project of the U.S. National Geodetic Survey plans to
collect airborne gravity data across the entire U.S. and its
holdings over the next decade. The goal of the project is to
create a gravimetric geoid model to use as the vertical datum for
the U.S. by 2021. Airborne gravity survey work began more than
two years ago, with Alaska as a high priority for new data
collection. Data collection there is underway and will be ongoing
for several more years, but two roughly 400 km x 400 km surveys
have been completed: in 2008 (centered over Cook Inlet near
Anchorage) and in 2009 (centered over the Interior, to the north
of the Alaska Range and west of Fairbanks). The gravity data for
both surveys was collected with a MicroG LaCoste TAGS system but
each survey utilized a different aircraft and survey layout. The
2008 survey was flown at 35,000 ft with the NOAA Cessna Citation
jet, with 10 km data line spacing and 60 km cross lines spacing.
The 2009 survey was flown at 12,500 ft with the Naval Research
Lab King Air (RC-12) turboprop, with 7.5 km data line spacing and
37.5 cross line spacing. The 2008 data reveal the > 20 km
resolution gravity effects of all the near-trench features (from
accretionary prism to volcanic arc) for a 400 km stretch of the
active plate boundary. In comparison, the 2009 gravity data allow
a slightly better resolution (>15 km) view of the distal
deformation to the north of the Alaska Range. The free-air
gravity disturbances for each survey were computed and then
complete (terrain-corrected) Bouguer gravity anomalies were
calculated with Gauss-Legendre Quadrature integration (von Frese,
et al., 1999) using standard density assumptions. Topography used
to calculate the corrections came from the freely-available
GTOPO30 (USGS, online) and bathymetry from the Smith and Sandwell
(1997) altimetry-derived data. Interpretations of the complete
Bouguer gravity anomalies will be made in the context of the
tectonic activity in southern Alaska.
|
Download (pdf) (20.72 MB)
|
Geophysical and Geodetic Analysis of Airborne Gravity Data from
GRAV-D in Alaska
|
Theresa M. Diehl
|
Theresa M. Diehl
|
Vicki Childers and Sandra Preaux
|
2009/12/18
|
San Francisco, CA
|
American Geophysical Union Fall Meeting
|
Airborne gravity, GRAV-D, geodesy, tectonics, Alaska
|
Show Abstract
The U.S. National Geodetic Survey’s mission is to define and
maintain the spatial reference system of the United States.
Official policy, adopted in 2008, calls for the definition a new
national vertical datum based on a gravimetric geoid by 2018 and
for its maintenance into the future. The project that will
accomplish data collection and analysis tasks toward that goal is
called GRAV-D (Gravity for the Redefinition of the American
Vertical Datum). The project is underway to collect new airborne
gravity data across the entire U.S. To date, GRAV-D has collected
nearly 1 million sq km of high-altitude airborne gravity data at
12,500 ft to 35,000 ft. Data sets exist in Alaska, Puerto Rico
and the Virgin Islands, and the coastal Gulf of Mexico from the
Florida panhandle to the Mexican border. In support of the GRAV-D
mission, information about the geologic setting of the data sets
and geophysical interpretations of the gravity data are
necessary. For instance, geodetic concerns about knowledge of an
area’s density structure for completing geoid calculations within
topography can be addressed with geophysical interpretation
techniques. Here we examine GRAV-D data located in a tectonically
and topographically complex area of the country near Anchorage,
AK and Fairbanks, AK. We assess the contribution of information
gained from gravity analysis techniques, combined with
information from geologic studies, for geodetic application in
the area.
|
Download (pdf) (25.33 MB)
|
GRAV-D Part I: NGS' Gravity for the Re-definition of the American
Vertical Datum Project
|
Theresa M. Diehl
|
Vicki Childers
|
Dan Roman, Dru Smith, and Theresa M. Diehl
|
2009/09/02
|
Buenos Aires, Argentina
|
International Association of Geodesy Scientific Assembly
|
Airborne gravity, GRAV-D, geodesy, vertical datum,
|
Show Abstract
The mission of NOAA's National Geodetic Survey (NGS) is to
"define, maintain and provide access to the National Spatial
Reference System" (NSRS). NAVD 88 (North American Vertical Datum
of 1988) provides the vertical reference for the NSRS.
Comparisons with the Gravity Recovery and Climate Experiment
(GRACE) satellite gravity data have demonstrated significant
problems with NAVD 88. As repairing NAVD 88 through a massive
leveling effort is impractical, NGS has decided to establish a
gravimetric geoid as the vertical reference. The linchpin in
NGS's effort is the Gravity for the Redefinition of the American
Vertical Datum (GRAV-D) program, which will ultimately
incorporate satellite, airborne and terrestrial gravity data to
build the geoid accurate to 1-2 cm that the U.S. surveying public
requests. The GRAV-D program has two thrusts. First, a "high
resolution snapshot" one-time measurement campaign with dense
spatial sampling but short temporal span would be used to repair
and improve existing gravity holdings. This campaign would
involve airborne gravity surveys conducted over coastal areas
first and interior areas later for the entire US and its
holdings. Second, a "low resolution movie" will monitor temporal
changes to the gravity field by tracking low order and degree
changes in GRACE gravity data (Gravity Recovery and Climate
Experiment satellite) augmented with a recurring terrestrial
survey in areas of most rapid temporal changes. This effort would
involve time series of absolute and relative terrestrial gravity
measurements at these areas to help update the geoid over time.
Initial data collection supporting GRAV-D was completed in July
2008. An airborne survey based out of Anchorage, AK covered an
area 500 x 400 km over Cook Inlet and Kachemak Bay in 24 flights
and about 100 flight hours. Funding from the US Army Corps of
Engineers has facilitated surveying along the Coast of the Gulf
of Mexico during the fall and winter, and a region covering
Puerto Rico and the Virgin Islands. We present our project plan
and most recent results.
|
Download (ppt) (10.92 MB)
|
GRAV-D Part II : Examining airborne gravity processing assumptions
with an aim towards producing a better gravimetric geoid
|
Theresa M. Diehl
|
Theresa M. Diehl
|
Sandra Preaux, Vicki Childers, Dan Roman, Dru Smith, and Jarir Saleh
|
2009/09/02
|
Buenos Aires, Argentina
|
International Association of Geodesy Scientific Assembly
|
Airborne gravity, Kinematic GPS, GRAV-D, geodesy, software
development
|
Show Abstract
The mission of NOAA's National Geodetic Survey (NGS) is to
"define, maintain and provide access to the National Spatial
Reference System" (NSRS). NAVD 88 (North American Vertical Datum
of 1988) provides the vertical reference for the NSRS.
Comparisons with the Gravity Recovery and Climate Experiment
(GRACE) satellite gravity data have demonstrated significant
problems with NAVD 88. As repairing NAVD 88 through a massive
leveling effort is impractical, NGS has decided to establish a
gravimetric geoid as the vertical reference. The linchpin in
NGS's effort is the Gravity for the Redefinition of the American
Vertical Datum (GRAV-D) program, which will ultimately
incorporate satellite, airborne and terrestrial gravity data to
build the geoid accurate to 1-2 cm that the U.S. surveying public
requests. The GRAV-D program has two thrusts. First, a "high
resolution snapshot" one-time measurement campaign with dense
spatial sampling but short temporal span would be used to repair
and improve existing gravity holdings. This campaign would
involve airborne gravity surveys conducted over coastal areas
first and interior areas later for the entire US and its
holdings. Second, a "low resolution movie" will monitor temporal
changes to the gravity field by tracking low order and degree
changes in GRACE gravity data (Gravity Recovery and Climate
Experiment satellite) augmented with a recurring terrestrial
survey in areas of most rapid temporal changes. This effort would
involve time series of absolute and relative terrestrial gravity
measurements at these areas to help update the geoid over time.
Initial data collection supporting GRAV-D was completed in July
2008. An airborne survey based out of Anchorage, AK covered an
area 500 x 400 km over Cook Inlet and Kachemak Bay in 24 flights
and about 100 flight hours. Funding from the US Army Corps of
Engineers has facilitated surveying along the Coast of the Gulf
of Mexico during the fall and winter, and a region covering
Puerto Rico and the Virgin Islands. We present our project plan
and most recent results.
|
Download (ppt) (1.88 MB)
|
Introduction to Gravity
|
Theresa M. Diehl
|
Theresa M. Diehl
|
|
2009/03/10
|
Austin-Bergstrom Airport; Austin, TX
|
University of Texas at Austin's "Intro to Geophysics" class visit to
NGS field work
|
Gravity, geodesy, instrumentation, data processing, gravity
interpretation, GRAV-D
|
Show Abstract
This presentation gives a short overview of gravity in relation
to geodesy, as well as the instruments, processing, and
interpretation involved in conducting airborne gravity studies.
The slides are meant for a general audience or non-geology
undergraduate student level.
|
Download (ppt) (3.81 MB)
|
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska
|
Vicki A. Childers
|
Vicki A. Childers
|
Daniel R. Roman
|
2011/02/24
|
Anchorage, Alaska
|
45th Annual Alaska Surveying & Mapping Conference
|
GRAV-D, gravity, geoid, vertical datum, Alaska
|
Show Abstract
Starting in 2008, airborne observations were made by the National
Geodetic Survey over the state of Alaska. These data have been
refined into aerogravity for use in developing geoid height
models to serve as a future vertical datum. While the collection
over the state is far from complete, the data processed thus far
demonstrate the expected changes brought about by a consistent
and seamless aerogravity campaign as a part of the Gravity for
the Redefinition of the American vertical Datum (GRAV-D) project.
This work shop will cover aspects of the collection as well as
the net change to the gravimetric geoid model for some regions of
Alaska. This is not yet a complete look, since not all of the
data have been collected yet. However, it should provide insight
into what the final model will look and the expected reliability
of a future Alaskan vertical datum.
|
Download (ppt) (6.72 MB)
|
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Part
II
|
Vicki A. Childers
|
Vicki A. Childers
|
Daniel R. Roman
|
2011/02/24
|
Anchorage, Alaska
|
45th Annual Alaska Surveying & Mapping Conference
|
GRAV-D, gravity, geoid, vertical datum, Alaska
|
Show Abstract
Starting in 2008, airborne observations were made by the National
Geodetic Survey over the state of Alaska. These data have been
refined into aerogravity for use in developing geoid height
models to serve as a future vertical datum. While the collection
over the state is far from complete, the data processed thus far
demonstrate the expected changes brought about by a consistent
and seamless aerogravity campaign as a part of the Gravity for
the Redefinition of the American vertical Datum (GRAV-D) project.
This work shop will cover aspects of the collection as well as
the net change to the gravimetric geoid model for some regions of
Alaska. This is not yet a complete look, since not all of the
data have been collected yet. However, it should provide insight
into what the final model will look and the expected reliability
of a future Alaskan vertical datum.
|
Download (ppt) (12.23 MB)
|
Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Part
III
|
Daniel R. Roman
|
Daniel R. Roman
|
Vicki A. Childers
|
2011/02/24
|
Anchorage, Alaska
|
45th Annual Alaska Surveying & Mapping Conference
|
GRAV-D, gravity, geoid, vertical datum, Alaska
|
Show Abstract
Starting in 2008, airborne observations were made by the National
Geodetic Survey over the state of Alaska. These data have been
refined into aerogravity for use in developing geoid height
models to serve as a future vertical datum. While the collection
over the state is far from complete, the data processed thus far
demonstrate the expected changes brought about by a consistent
and seamless aerogravity campaign as a part of the Gravity for
the Redefinition of the American vertical Datum (GRAV-D) project.
This work shop will cover aspects of the collection as well as
the net change to the gravimetric geoid model for some regions of
Alaska. This is not yet a complete look, since not all of the
data have been collected yet. However, it should provide insight
into what the final model will look and the expected reliability
of a future Alaskan vertical datum.
|
Download (ppt) (8.17 MB)
|
New England Height Issues
|
Dan Martin
|
Dan Martin
|
|
2009/12/10
|
Nashua, NH
|
New England State Surveying Societies
|
Height, New England, Height-Mod
|
|
Download (ppt) (3.27 MB)
|
Modernization of the National Spatial Reference System
|
Dan Martin
|
Dave Doyle
|
Dan Martin
|
2011/01/20
|
Verona, NY
|
NYSAPLS
|
Datum, Geoid, Height, Modernize, NSRS,
|
|
Download (ppt) (33.89 MB)
|
VT State Plane
|
Dan Martin
|
Dan Martin
|
|
2008/04/11
|
Rutland, Vermont
|
Vermont Society of Land Surveyors
|
Coordinates, State Plane, Vermont
|
|
Download (ppt) (9.53 MB)
|
Height Modernization Activities at HGSD
|
Cliff Middleton
|
Cliff Middleton
|
|
2009/06/08
|
Beaumont, TX
|
Height Modernization Forum
|
PAMS, Bench Marks, Extensometer, CORS
|
An overview of Height Modernization Activities at the Harris
Galveston Subsidence District.
|
Download (pptx) (26.38 MB)
|
Vermont CORS (VECTOR) Benefits
|
Dan Martin
|
Dan Martin
|
|
2009/02/02
|
Montpelier
|
VTrans Monthly Survey Meetying
|
Vermont, CORS, NSRS, RTN, Benefit, RTK,
|
Show Abstract
The use of the Global Positioning System (GPS) for positioning
and mapping has been steadily increasing since its introduction
in the late 1980’s. In the last few years, the use of GPS has
exploded, primarily due to the establishment of regional or
state-wide CORS networks that provide real-time correction data.
The Vermont Agency of Transportation (VTrans) is in the process
of building such a network with its primary purpose to support
accurate positioning and mapping along Vermont’s Interstate
corridors and other major highways. CORS are geodetic quality GPS
receivers and antennas that are permanently installed. These
stations collect GPS data continuously, and transmit data via the
Internet to a central server. At the server, the data is archived
for future use, and made available for download by any user. The
incoming data is also processed at the server to generate
corrections which are made available over the Internet to users
in real-time. The Vermont Network has been named VECTOR (Vermont
Enhanced CORS and Transmission Of Real-time corrections) to
emphasize the expanded range of products available. The VT CORS
Network has provided significant benefit to VTrans users and the
tax payers of VT, and supports a variety of different
applications from a diverse user community outside of VTrans. The
information in this report shows that the direct savings VTrans
has realized will likely pay for the system by the end of 2009,
indicating a three-year return on investment. When considering
the total savings realized by all users, the system paid for
itself many times over in 2008 alone.
|
Download (pptx) (4.32 MB)
|
Vermont Enhanced CORS and Transmission of Real-time Corrections -
Network Status and Current Applications
|
Dan Martin
|
Dan Martin
|
|
2008/12/19
|
Montpelier
|
Vermont Society of Land Surveyors
|
CORS, OPUS, Vermont, RTN
|
This presentations was designed to show the development and usage of
CORS in Vermont.
|
Download (ppt) (8.87 MB)
|
Status the Vertical Network in NE and Modernization of the Vertical
Datum
|
Dan Martin
|
Dan Martin
|
|
2010/08/11
|
Concord, MA
|
USACE Vertical Datums Workshop
|
Vertical Datum, NGS 10 year plan, height-mod, modernize, CORS
|
Show Abstract
A presentation showing the current status of the vertical network
in New England, and highlighting the need to modernize. The
presentation discusses the rational for modernizing as discussed
in the 10-year plan.
|
Download (ppt) (2.50 MB)
|
Public Sector Networks - Vermont
|
Dan Martin
|
Dan Martin
|
|
2010/08/06
|
Durham, NH
|
NE Real-Time Summit
|
Height, New England, Height-Mod, Real-time, CORS, RTK
|
|
Download (pptx) (2.65 MB)
|
Vertical Datums and Heights
|
Dan Martin
|
Dan Martin
|
|
2008/10/06
|
Montpelier, VT
|
VTrans Monthly Survey Meetying
|
Heights, vertical datums
|
|
Download (ppt) (9.43 MB)
|
County Scorecard and GPRA Measures
|
Brett Howe
|
Brett Howe
|
Monica Stich, Joe Whitsitt
|
2010/05/20
|
Silver Spring, MD
|
NGS Convocation
|
County Scorecard, GPRA, Convocation, stakeholder feedback, web
survey, performance measures, GRAV-D, OPUS, National Association of
County Engineers, NACE, OMB
|
Show Abstract
Presentation given to NGS employees and stakeholders at the 2010
NGS Convocation in Silver Spring, MD. The presentation goes over
the NGS County Scorecard web survey results from a 2010 survey of
over 500 members of the National Association of County Engineers
or NACE. An overview is given of the current NGS Government
Performance and Results Act or GPRA performance measure that
includes the County Scorecard web survey as well as plans for a
new replacement GPRA measure which tracks the progress of NGS'
Gravity for the Redefinition of the American Vertical Datum
(GRAV-D) initiative.
|
Download (pdf) (1.26 MB)
|
NSRS, CORS and GRAV-D Socioeconomic Scoping Study Congressional
Rollout
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2009/06/15
|
Washington, DC
|
Congressional Briefing
|
Congressional Briefing, CORS, NSRS, GRAV-D, socioeconomic benefits,
Congress
|
Show Abstract
This is a .wav file of the NGS Director's opening remarks to
congressional staffers and stakeholders during the rollout to
Congress of a 2009 socio-economic benefits study of the NSRS,
CORS and GRAV-D components. The full study is available here:
http://www.ngs.noaa.gov/PUBS_LIB/Socio-EconomicBenefitsofCORSandGRAV-D.pdf
A one page overview of the study is available here:
http://www.ngs.noaa.gov/INFO/OnePagers/socio_eco_handout.pdf
|
Download (wav) (41.17 MB)
|
Building on Geodetic History for a Geospatial Future
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2009/07/11
|
San Diego, CA
|
ESRI Survey & Engineering GIS Summit
|
keynote, NGS Overview, history, NSRS, NGS Products and Services, NSRS
Expansion Video, Norfolk flooding simulation
|
Show Abstract
This presentation is from the the keynote speech given by the NGS
Director at the 2009 ESRI Survey & Engineering GIS Summit.
Discusses the history, importance and future of the National
Spatial Reference System (NSRS).
|
Download (ppt) (39.77 MB)
|
NGS 101 for HSRP New Members
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2011/03/25
|
Silver Spring, MD
|
Hydrographic Services Review Panel (HSRP) New Member Orientation
|
NGS Overview, NSRS, HSRP
|
Show Abstract
Brief NGS 101 and overview given by the NGS Director to new
Hydrographic Services Review Panel (HSRP) members
|
Download (ppt) (23.96 MB)
|
Federal Geodetic Control Subcommittee Update
|
Ronnie Taylor
|
Ronnie Taylor
|
|
2011/01/11
|
Silver Spring, MD
|
Federal Geographic Data Committee (FGDC) Coordination Group Meeting
|
FGCS, FGDC, NSRS, NGS Overview, interagency
|
Show Abstract
Acting NGS Director, Ronnie Taylor, presents an update of Federal
Geodetic Control Subcommittee(FGCS)activities to the Federal
Geographic Data Committee (FGDC). FGCS website is:
http://www.fgdc.gov/participation/working-groups-subcommittees/fgcs
|
Download (ppt) (7.73 MB)
|
Latest Advancements at the National Geodetic Survey
|
Ronnie Taylor
|
Ronnie Taylor
|
|
2011/01/25
|
Washington, DC
|
Transportation Research Board 90th Annual Meeting
|
TRB, NGS Overview, NGS Products and Services
|
Show Abstract
Acting NGS Director, Ronnie Taylor, presentation to the
Transportation Research Board 90th Annual Meeting. Provided an
update on NGS activities including: new geopotential and vertical
datums efforts, VDatum,GRAV-D, OPUS, LOCUS, Height Modernization,
and Aeronautical Survey Program.
|
Download (ppt) (1.61 MB)
|
NGS HSRP Update
|
Ronnie Taylor
|
Ronnie Taylor
|
|
2010/10/13
|
Vancouver, Washington
|
Hydrographic Services Review Panel (HSRP) Public Meeting
|
HSRP, NGS Accomplishments, NGS Overview, NGS Update, NGS Products and
Services
|
Show Abstract
Acting NGS Director, Ronnie Taylor, update on NGS activities and
2010 accomplishments to the HSRP, including: Top 2010
Accomplishments, CORS, Shoreline Mapping, VDatum, County
Scorecard, FY 2011 President's Budget and planned 2011
milestones.
|
Download (ppt) (2.17 MB)
|
National Geodetic Survey Update
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2010/05/06
|
Providence, RI
|
Hydrographic Services Review Panel (HSRP) Public Meeting
|
HSRP, NGS Updae, NGS Overview, NGS Update, ARRA, NGS Products and
Services
|
Show Abstract
NGS Director, Juliana Blackwell, provides an update to the HSRP
on NGS activities including FY2010 performance measures,
shoreline mapping ARRA funding, VDatum, Height Modernization,
GRAV-D, Haiti earthquake response, Deepwater Horizon response,
NGS 2010 milestones, FY2011 President's Budget and the Federal
Geospatial Summit.
|
Download (ppt) (5.55 MB)
|
NGS Programs and Geodetic Tools, Part II
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/03/07
|
Las Vegas, NV
|
CLSA/NALS Conference 2011
|
Geodetic Control, HTDP, VDATUM, NSPS Surveying, Datasheets,
California, GEOID09
|
Show Abstract
The California advisor and newly-appointed SW Region advisor will
give updates on some of NGS' more popular programs, including the
CORS network, OPUS, and DSWorld software. In response to
requests, a review of the Datasheet fields and clarification of
textual metadata will be provided. In light of increasing
concerns about planning for Sea Level Rise, there will be a brief
primer on tidal datums and usage of VDATUM software, which
incorporates geodetic datums. Looking to the future, we will
discuss the adoption of ITRF2008 for CORS coordinates, the shift
to absolute antenna calibrations, and the migration-- in a decade
or so-- to completely new horizontal and vertical datums.
|
Download (pptx) (30.99 MB)
|
National Geodetic Survey - Programs & Geodetic Tools - Part I
|
William Stone
|
William Stone
|
|
2011/03/07
|
Las Vegas, NV
|
California Land Surveyors Association/Nevada Association of Land
Surveyors Annual Conference
|
CORS, OPUS, datums, NAD83, ITRF, Ten-Year Plan
|
|
Download (pptx) (15.07 MB)
|
NGS Programs and Geodetic Tools
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/01/28
|
Fresno, CA
|
CSUF Geomatics Conference, 50th
|
Geodetic control, OPUS, HTDP, Reference frames, VDATUM, future
national datums, Datasheets, NSPS Surveying
|
Show Abstract
The California advisor will give updates on some of NGS' tools
and programs, including OPUS (data submission), as well as
visualization tools such as DSWorld software and the Advisor's
mapping website. A review of the Datasheet fields and
clarification of textual metadata will be provided. In light of
increasing concerns about planning for Sea Level Rise, there will
be a brief primer on tidal datums and usage of VDATUM software,
which incorporates geodetic datums. You will be informed about
proposed changes in geodetic reference systems-- the adoption of
ITRF2008 and the shift to absolute antenna calibrations impacting
CORS coordinates this Spring, and the migration in a decade or so
to completely new horizontal and vertical datums.
|
Download (pptx) (16.50 MB)
|
Overview of NOAA's National Shoreline Mapping in the National
Geodetic Survey
|
Douglas Graham
|
Douglas Graham
|
|
2011/03/24
|
Myrtle Beach, SC
|
Coastal GeoTools 2011
|
Shoreline, National Shoreline, shoreline indicators, Coastal Mapping
Program, CSCAP, Emergency Response Imagery, VDATUM, LiDAR
|
Show Abstract
"Survey of the Coast", a predecessor of the National Ocean
Service within the National Oceanic and Atmospheric
Administration, is the oldest American civilian scientific agency
established in 1807, to survey and map the nation's coastline.
This organization also became the first agency to collect masses
of geographic information (geodetic control, tidal, shoreline,
soundings, geomagnetic, etc.) and processed this information to
produce products for the safety and welfare of our citizens.
Today the National Geodetic Survey continues to provide products
and standards, including the national shoreline and derivatives
including ortho imagery, processed lidar, and FGDC metadata to
meet our nation's economic, social, and environmental needs. The
National Geodetic Survey also provides emergency response imagery
and lidar to support homeland security and emergency response
requirements. The data is available through GeoSpatial One Stop,
Digital Coast, and NOAA Shoreline Data Explorer applications.
|
Download (ppt) (29.60 MB)
|
New Coordinates for CORS Sites & Oregon Case Study
|
Mark L. Armstrong
|
Giovanni Sella, Jake Griffiths, Mark Armstrong
|
Giovanni Sella, jake Griffiths
|
2011/03/25
|
Salem, Oregon
|
ODOT Surveyors Conference
|
MYCS, Oregon, CORS96a
|
|
Download (ppt) (6.06 MB)
|
Modeling uncertainty in lidar-derived NOAA shoreline
|
Christopher Parrish
|
Christopher Parrish
|
Stephen White, Shachak Pe'eri, Brian Calder, Yuri Rzhanov
|
2010/05/27
|
Mobile, AL
|
JALBTCX Annual Airborne Coastal Mapping and Charting Workshop
|
shoreline mapping, lidar, uncertainty
|
Show Abstract
NOAA's National Geodetic Survey (NGS) is mandated to map the
National Shoreline, the legally-recognized shoreline depicted on
NOAA nautical charts. While the primary application of this
shoreline is in support of safe navigation, the data are now
being used for an increasingly wide range of coastal science
applications, including understanding and responding to threats
of climate change. Over the past decade, NGS has collaborated
with academic, government, and private sector partners to develop
and implement new lidar-based shoreline mapping procedures.
However, while NGS' lidar shoreline mapping workflow is now
beginning to be used operationally, rigorous methods of assessing
the uncertainty in the lidar-derived shoreline position have
lagged behind in development. The study presented here aims to
address this issue through development and comparison of two new
methods of assessing uncertainty in NOAA lidar-derived shoreline...
|
Download (pdf) (2.67 MB)
|
GRAV-D
|
Ronnie L. Taylor
|
Ronnie L. Taylor
|
|
2009/02/04
|
Vicksburg, Mississippi
|
Mississippi Association of Professional Surveyors Conference
|
Gravity for the Re-definition of the American Vertical Datum, Gravity and Heights are inseparably connected
|
|
Download (ppt) (5.38 MB)
|
NOAA's NGS US Height Reference System Modernization Plan
|
Ronnie L. Taylor
|
Ronnie L. Taylor
|
|
2009/03/21
|
Ottawa, Canada
|
Annual Canadian Geodetic Reference System Committee (CGRSC) Meeting
|
Why isn't NAVD 88 good enough anymore?, Height Modernization, Ten year plan, GRAV-D
|
|
Download (ppt) (13.67 MB)
|
NGS - A National Perspective
|
Ronnie L. Taylor
|
Ronnie L. Taylor
|
|
2010/04/01
|
Riverside, California
|
California Land Surveyors Association
|
Mission Overview, History, Challenges, NGS 10-Year Plan, NGS Programs, Regional and State Information
|
|
Download (ppt) (40.35 MB)
|
National Geodetic Survey HSRP Update
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2011/05/04
|
Honolulu, HI
|
Hydrographic Services Review Panel (HSRP) Public Meeting
|
NSRS, HSRP, milestones, performance measures, GPRA, NGS Update, NGS Budget, NGS Activities
|
Show Abstract
NGS Director, Juliana Blackwell, provides an update to the HSRP on NGS
activities including FY2011 and FY2012 information on performance measures,
significant activities, milestones and budget.
|
Download (ppt) (1.87 MB)
|
The State of NGS
|
Ronnie L. Taylor
|
Ronnie L. Taylor
|
|
2010/07/10
|
San Diego, California
|
ESRI Survey & Engineering GIS Summit
|
Mission Overview, History, Challenges, NGS 10-Year Plan, NGS Programs and Regional and State Information
|
|
Download (ppt) (17.74 MB)
|
NGS Products and Services Update
|
Dave Rigney
|
Dave Rigney
|
|
2010/02/25
|
Lansing, MI
|
2010 Michigan Society of Professional Surveyors
|
Products and Services
|
|
Download (pptx) (0.49 MB)
|
Overview of Datums Commonly Used in Michigan and the National Spatial
Reference System
|
Dave Rigney
|
Dave Rigney
|
|
2011/02/24
|
Frankenmuth, MI
|
Michigan Society of Professional Surveyors
|
Datums NSRS
|
|
Download (ppt) (6.35 MB)
|
Diving Deeper: Remote Sensing Podcast
|
Christopher Parrish
|
Christopher Parrish
|
|
2010/10/07
|
University of New Hampshire, Durham, NH
|
NOS Podcast
|
remote sensing, aerial imagery, satellite imagery, lidar, radar
|
|
Download (mp3) (25.77 MB)
|
IGS08: Elaboration, consequences and maintenance of the IGS
realization of ITRF2008
|
Paul Rebischung
|
Paul Rebischung
|
P. Rebischung, B. Garayt, R. Schmid, J. Ray, X. Collilieux
|
2011/04/07
|
Vienna, Austria
|
European Geosciences Union 2011
|
global reference frames, IGS, GPS
|
Show Abstract
IGS08: Elaboration, consequences and maintenance of the IGS
realization of ITRF2008 The International GNSS Service (IGS) has
designated its own realization of ITRF2008, known as IGS08, as
the basis of its products starting in early 2011 and for the next
full reprocessing campaign. The philosophy generally follows IGS
practice since 2000 when the IGS97 realization of ITRF97 was
adopted. However, unlike frames IGS97 through IGS05, IGS08 was
initially intended to be a direct subset of well performing,
stable GNSS stations from ITRF2008 rather than a separate
GNSS-only frame solution. But, while the IGS contribution to
ITRF2008 was computed using the original set of “absolute�
GNSS antenna calibrations (igs05.atx), IGS08 had to be consistent
with the latest set of calibrations (igs08.atx) that includes new
determinations for some existing antennas. Coordinate corrections
due to the antenna calibration updates were thus estimated and
applied when possible to the ITRF2008 coordinates of 64 affected
stations (out of a total of 232 stations in IGS08). As regards
GNSS, the scale of the terrestrial frame is highly correlated
with the satellite phase center offsets (PCOs) in the radial
Earth direction. As the ITRF2008 scale differs by about -1 ppb
from ITRF2005, new satellite PCOs consistent with ITRF2008 and
IGS08 had to be derived for igs08.atx. They were obtained by
back-solving the reprocessed solutions of five IGS analysis
centers, while fixing their scales to the ITRF2008 scale. In
order to satisfy regional users, many reference stations were
selected in areas with dense GNSS coverage, such as Europe. This
led to density heterogeneities in the IGS08 network, which is not
optimal for the alignment of global frames. So a smaller, well
distributed core network was additionally defined and recommended
for global applications (such as for the IGS core products).
Simulations show that using this core network instead of the full
IGS08 set as reference frame indeed significantly reduces the
“network effect�. Transformation parameters from IGS05 to
IGS08 are unsurprisingly close to those from ITRF2005 to
ITRF2008. Rotations are at the level of 0.01 mas so that the IGS
orbits and Earth orientation parameters should be marginally
affected by the switch from IGS05 to IGS08. But the scale
difference of ~ -1 ppb and the Z translation of ~6 mm will result
in changes in station positions by several millimeters. IGS08 is
already beginning to suffer from continuous loss of reference
stations due to earthquakes and mainly antenna changes, as was an
even more critical problem for IGS05. To avoid a future crisis
situation for the IGS products, it might be necessary to consider
regular updates of the IGS08 reference frame before the next ITRF
release. Such updates would require updated, post-discontinuity
IGS08 coordinates to be estimated. A method to obtain such
updated reference coordinates, based on the IGS operational
cumulative solution, will be proposed.
|
Download (pdf) (2.27 MB)
|
Status of IGS orbit modeling & areas for improvement
|
Jim Ray
|
Jim Ray
|
Jake Griffiths
|
2011/04/08
|
Vienna, Austria
|
European Geosciences Union 2011
|
orbits, IGS, GPS
|
Show Abstract
Status of IGS Orbit Modeling and Areas for Improvement J.R. Ray
(jim.ray@noaa.gov) J. Griffiths (jake.griffiths@noaa.gov)
NOAA/NGS, Silver Spring, Maryland, US While the overall mean
inaccuracy of the recent Final orbits of the International GNSS
Service (IGS) is estimated to be about 2 cm (1D RMS), three
aspects of the orbit modeling can probably be significantly
improved: 1) ensure consistent and accurate modeling of satellite
attitude variations; 2) mitigate spurious rotations of the
constellations; and 3) add accelerations due to Earth radiation
pressure. The errors associated with these are all highly
systematic, not random. Reliable models for the attitude control
of the older GPS satellites have been published for some years.
Recently new models have been developed for GLONASS and the
newest generation of GPS satellites as well. However, the
implementation of these models among IGS Analysis Centers (ACs)
is not consistent. Partly this is probably because the GPS Block
IIR spacecraft were designed in such a way that attitude effects
were nearly benign, so the major analysis errors were for the
older, dwindling generations. However, with newer constellations
and GPS Blocks the attitude variations probably cannot be treated
so simply for high-accuracy results. The impact on user products
is mostly on satellite clock variations and therefore on precise
point positioning (PPP) results. So it is vital to ensure overall
consistency by the IGS ACs adopting common models to generate
combined products and by users implementing the same models in
their PPP solutions. A leading error in the current IGS orbits is
spurious net rotations of the constellation. It was learned in
the early years of the IGS that once-per-revolution empirical
parameters (or similar) were needed to model subdaily effects of
solar radiation pressure. Failing to do so caused mainly large
translational offsets in the Y component of the GPS orbit origin.
But even with the higher-order parameterizations, much smaller
rotational errors remain. The spectral features of these seem
strongest near odd multiples of the GPS draconitic frequency
(1.04 cycles per year) and probably also near fortnightly
periods. Deficiencies in the widespread once-per-rev empirical
modeling are likely to be responsible for these rotational
errors. Most IGS ACs neglect the satellite accelerations due to
reflected and thermally emitted radiation from the Earth as well
as recoil thrust from the GNSS transmitters, largely because an
accepted model for GNSS spacecraft is not yet available. Studies
indicate that including at least the Earth albedo effect could
remove most of the observed 2 cm bias between IGS orbits and
satellite laser ranging. So developing an acceptable model and
implementing it should be a high near-term priority for the IGS.
|
Download (ppt) (2.46 MB)
|
State Plane Coordinates (webinar)
|
Dave Doyle
|
Dave Doyle
|
|
2010/12/08
|
Silver Spring, MD
|
webinar open to public
|
State Plane Coordinates, ellipsoid, grid scale factor, map
projections
|
|
Download (zip) (0.00 MB)
|
NGS Geodetic Toolkit
|
Curt Smith
|
Curt Smith
|
|
2011/03/03
|
Spokane, Washington
|
LSAW-ISPLS-WFPS Conference 2011
|
Geodetic Toolkit
|
Show Abstract
NGS Geodetic Tool Kit; a 2-hour Seminar The NGS Geodetic Tool Kit
includes several geodetic computational utilities including the
geoid computation utilities, HTDP, LVL_DH, the geodetic inverse
and forward utilities, OPUS, gravity prediction utilities,
NADCON, VERTCON, and the XYZ to latitude, longitude, height
conversion utility. Some utilities you use every day and some you
don’t. You probably don’t need to compute a geodetic inverse
very often, or convert from geocentric coordinates X, Y, and Z to
latitude, longitude, and ellipsoid heights on a daily basis, so
you probably don’t have these utilities on your personal
computer. But, when you need them they can be found in the NGS
Geodetic Tool Kit! This workshop will highlight many of these
utilities and describe their expected output and usage.
|
Download (ppt) (29.77 MB)
|
GPS-Derived Heights, Focus on NGS 59 Guidelines
|
David Zilkoski
|
David Zilkoski
|
|
2010/05/13
|
Silver Spring, MD
|
webinar open to the public
|
types of heights and their accuracies, GPS/GNSS error sources, NGS
58-Guidelines for Establishing GPS-Derived Ellipsoid Heights, NGS
59-Guidelines for Establishing GPS-Derived Orthometric Heights
|
|
Download (zip) (0.00 MB)
|
Introduction to Geodetic Vertical Datums
|
Dave Doyle
|
Dave Doyle
|
|
2010/03/02
|
Silver Spring, MD
|
webinar open to public
|
vertical datums, NAVD88, NGVD29, tidal datums, heights, Geoid model,
gravity data, CORS, OPUS
|
|
Download (zip) (0.00 MB)
|
OPUS Updates
|
Curt Smith
|
Curt Smith
|
|
2011/03/03
|
Spokane, Washington
|
LSAW-ISPLS-WFPS Conference 2011
|
OPUS
|
Show Abstract
On-line Positioning User Service (OPUS); a 2-hour Seminar The
National Geodetic Survey (NGS) operates the On-line Positioning
User Service (OPUS) as a means to provide GPS users easier access
to the National Spatial Reference System (NSRS). OPUS allows
users to submit their GPS data files to NGS, where the data will
be processed to determine a position using NGS computers and
software. The position for your data will be reported back to you
via e-mail in both the International Terrestrial Reference Frame
(ITRF) and NAD83 coordinates as well as Universal Transverse
Mercator (UTM), U.S. National Grid (USNG) and State Plane
Coordinates (SPC) northing and easting. Recent and proposed
developments regarding the various OPUS utilities will be
discussed.
|
Download (ppt) (31.11 MB)
|
Fundamentals of the National Spatial Reference System
|
Dave Doyle
|
Dave Doyle
|
|
2009/12/09
|
Silver Spring, MD
|
webinar open to the public
|
CORS, OPUS, HARN, ITRF, geoid, ellipsoid
|
|
Download (zip) (1.10 GB)
|
GPS-Derived Heights 1/2-Day
|
Curt Smith
|
Curt Smith
|
Dave Zilkoski, Ed Carlson, Chris Pearson
|
2011/03/03
|
Spokane, Washington
|
LSAW-ISPLS-WFPS Conference 2011
|
GPS-Derived Heights, Ellipsoid Heights, Orthometric Heights, Geoid
Heights
|
Show Abstract
GPS-Derived Heights ; a 4-hour Seminar GPS-Derived Heights is a
1/2-day seminar detailing heights, height systems, their
relationships, and development through the use of the Global
Positioning System (GPS). Discussion describes the use of NGS
GPS-Derived Ellipsoid and Orthometric Heights Guidelines.
Development of sample projects and analysis of example baseline
processing and project adjustments illustrate the basic concepts
outlined. This seminar addresses both large scale and "local"
projects, the use of the Continuously Operating ReferenceStations
(CORS), On-line Positioning User Service (OPUS) and other NGS
products and services.
|
Download (ppt) (73.67 MB)
|
Geodetic Control Framework Theme
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/03/30
|
Fresno, CA
|
CalGIS 2011 Conference
|
GIS, CA Framework Theme, Geodetic Control,
|
Show Abstract
Geodetic control is one of seven core framework themes in the
California Geospatial Framework Data Plan document. Discussions
are underway within a Work Group under the auspices of the CA GIS
Council with regard to what type of geodetic control should be
considered 'framework' points, who in California would be the
steward for maintenance, and whether and how to incorporate
real-time data into this theme. National Geodetic Survey has been
responsible for providing an accurate National Spatial Reference
System and the NGS Geodetic Advisor for California, an active
member of the Work Group, will provide updates on the process of
defining, populating, and maintaining the geodetic control
framework layer in this state that has very active Earth surface
processes, both horizontally and vertically.
|
Download (pptx) (5.46 MB)
|
State of NGS 2011
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/04/07
|
Riverside, CA
|
LCSO presents State of NGS seminar
|
NGS Priority Program Division Updates 2011
|
Show Abstract
This presentation provided information about NGS accomplishments
in the past year and near-term future activities and was
organized into 3 sections. 1)Priority programs: CORS, OPUS,
GRAV-D with a subsection on GEOID09 in CA and OPUS-DB, and Ht
Mod; 2)Updates of activities in many of the branches within the 6
Divisions; and 3)NGS as part of NOAA, particularly collaboration
with CO-OPS.
|
Download (pptx) (21.42 MB)
|
A review of GPS and GRACE estimates of surface mass loading effects
|
Tonie van Dam
|
Tonie van Dam
|
X. Collilieux, Z. Altamimi, J. Ray
|
2011/04/05
|
Vienna, Austria
|
European Geosciences Union 2011 General Assembly
|
GRACE, GPS, loading, mass transport
|
Show Abstract
A review of GPS and GRACE estimates of surface mass loading
effects Tonie van Dam, Xavier Collilieux, Zuheir Altamimi, and
Jim Ray Since its launch in 2002, many authors have compared GPS
height coordinate residuals with radial displacements predicted
from the Gravity Recovery and Climate Experiment (GRACE). Most
comparisons have demonstrated significant annual correlations at
perhaps 50% - 75% of the sites. At the other sites, there exists
little to no correlation between the GPS observed and GRACE
predicted heights. The disagreement is often attributed to
problems in the GPS data analysis, e.g. ocean tide aliasing,
seasonal monument motion, or reference frame effects. In this
presentation, we revisit the GPS/GRACE comparison using GPS
height residuals, GRACE data, and an environmental loading model
in an attempt to better explain the discrepancy between the
signals. We will also compare the degree-1 in the GPS time series
with that from the environmental loading model.
|
Download (pdf) (2.38 MB)
|
Error analysis of the airborne gravity data collected over Alabama in
2008
|
Yan Ming Wang
|
YM Wang
|
C Huang, J Saleh, S Holmes, XP Li, DR Roman, S Preaux , T Dieh , V
Childers
|
2011/04/08
|
Vienna, Austria
|
EGU 2011
|
airborne gravity accuracy
|
Show Abstract
Abs. To access the quality of NGS airborne gravity system and the
impact of the flight altitude, NGS performed test flights at
1700, 6300 and 11000 meters altitudes in 2008, with track spacing
10 km for the two lower flights and 5 km for the highest flight.
The flights provide not only important data sets for testing the
precision and accuracy of the NGS airborne gravity system, but
also the impact of the flight altitude to the collected gravity
field. Results show that the system is stable and delivers high
quality gravity data at three altitudes. The gravity collected at
three altitudes agrees with each other from 1.4 to 3.3 mGal (RMS)
at 11000 m flight altitude. If the biases are removed, the
agreement is better than 1 mGal. At the ground, the downward
continued gravity anomalies from the three altitudes agree within
1.9 to 3.8 mGal (RMS). After the biases removed, the agreement is
better than 1.7 mGal. The similar results are obtained in
comparison with NGS2008 surface gravity. The overall agreement
between the downward continued airborne gravity at three
altitudes and the NGS2008 surface gravity are better than 1.7
mGal, after the mean values are removed. The flight altitude has
a direct impact on the airborne gravity accuracy. The comparisons
show that the gravity collected at 11000 m altitude performance
the worst, probably due to smaller signal/noise ratio and larger
downward continuation effect. Due to 10 km track spacing, the
gravity collected at 1700 m altitude does not outperform those
collected at 6700 m altitude. Gravity at these two altitudes
estimated to have an accuracy ±2 mGals at the ground.
|
Download (pptx) (2.57 MB)
|
Towards the unification of the vertical datums over the North
American continent
|
Yan Ming Wang
|
Dru Smith
|
M Véronneau, D Roman, J L Huang, YM Wang, M Sideris
|
2010/10/06
|
Marne-La-Vallee, France
|
Reference Frames for Applications in Geosciences (REFAG2010)
|
vertical datums, geoid
|
Show Abstract
The United Sates adopted the North American Vertical Datum of
1988 (NAVD 88) for its official vertical datum in the 1990s.
Canada has been using the Canadian Geodetic Vertical Datum
(CGVD28) for its height applications since the 1930s. The use of
the different datums causes inconsistent heights across the
border between the two countries, and the topographic height data
from the two countries are not compatible. Both datums rely on
passive control and significant pre-modern survey data, yielding
not only misalignment of the datums to the best known global
geoid at approximately 1-2 meters, but also local uplift and
subsidence issues which may significantly exceed 1-2 meters in
extreme cases. Today, the GNSS provides the geometric
(ellipsoidal) height to an accuracy of 1-2 centimeters globally.
Because of this, users have begun to demand a physical height
system that is closely related to the Earth’s gravity field to
a comparable accuracy. To address this need, government agencies
of both countries are preparing the next generation of vertical
datums. Even if the new datums are based on the same concepts and
parameters, it is possible to have inconsistent heights along the
borders due to the differences in the realization of the datums.
To avoid inconsistency, it is in the interest of both countries
to have a united, seamless, highly accurate vertical datum. The
proposed replacements for CGVD28 and NAVD88 shall be based on
GNSS positioning and a high accuracy gravimetric geoid that
covers the territories of the United States, Canada, Mexico and
the surrounding waters (to include all of Alaska, Hawaii, the
Caribbean and Central America). To account for the effect of the
sea level change, postglacial rebound, earthquakes and
subsidence, this datum will also provide information on these
changes. Detailed description of the definition, realization and
maintenance of the datum is proposed. The challenges in
realization and maintaining the datum are also discussed.
|
Download (pptx) (2.62 MB)
|
Investigation of the Topographic Effect by Using High Degree
Spherical Harmonic Expansion
|
Yan Ming Wang
|
Yan Ming Wang
|
|
2009/09/04
|
Buenos Aires
|
IAG Scientific Meeting 2009
|
topographic effect, spherical harmonc expansion
|
|
Download (ppt) (2.08 MB)
|
A comparison of different geoid computation procedures in the US
Rocky Mountains
|
Yan Ming Wang
|
Yan Ming Wang
|
H Denker, J Saleh, XP Li, DR Roman, D Smith
|
2010/09/22
|
University of Alaska Fairbanks, USA
|
Second International Symposium of the International Gravity Field
Service
|
gravity, geoid, comoputation methods
|
Show Abstract
The geoid over the US Rocky Mountains is computed using two
different procedures. The NGS group bases its geoid computations
on Helmerts 2nd condensation method and presents an approximate
and a precise version of it. The former is based on the Faye
anomaly, which involves approximations of the terrain effect and
the downward continuation of the surface gravity residuals to the
geoid. The precise version is based on accurate account of the
topographic masses and downward continuation. The second
procedure leans upon the European geoid modeling; it uses the
Molodenskii theory and converts height anomalies to geoid
heights. Both procedures employ EGM08 as a reference field and
SRTM-DTED1 (3") elevations. However, the two procedures use
different maximal degrees of EGM08 and utilize its low degrees
differently. The results are compared to GPS Bench Marks and the
resulting deflection models to astro-geodetic deflections.
|
Download (ppt) (7.95 MB)
|
On the Solutions of the Geodetic Exterior/Interior Fixed Boundary
Value Problems
|
Yan Ming Wang
|
Yan Ming Wang
|
|
2006/06/01
|
Wuhan University, China
|
Hotine-Marussi Symposium 2006
|
geodetic boundary value problems
|
Show Abstract
The biggest obstacle in solving the geodetic interior boundary
value problem is the unavailability of the mass density
distribution of the Earth. However, if the density of the
topography is known, solutions valid only in the topographic
masses can always be found after some mathematical manipulations.
The disturbing potential inside the topographic masses is
“harmonized� by subtracting a non-harmonic potential field.
The “harmonized� potential field is then solved by analytical
downward continuation. A solution for the non-harmonic potential
is presented for the special case where the mass density of the
topography is a constant.
|
Download (ppt) (0.14 MB)
|
Numerical aspects of the omission errors due to limited grid size in
geoid computations
|
Yan Ming Wang
|
Yan Ming Wang
|
|
2009/07/10
|
Rome, Italy
|
VII Hotine-Marussi Symposium
|
omission error, grid size
|
Show Abstract
Based on the assumption that the ultra-high frequencies of the
gravity field are produced by the topography variations, we
compute the omission errors by using 3 arc-second elevation data
from the Shuttle Radar Topography Mission (SRTM). It is shown
that the omission errors to the geoid are in the range of dm, cm
and sub-cm level for grid sizes of 5', 2' and 1' over the
contiguous United States (CONUS), respectively. The results
suggest that a 1 arc-minute grid size is sufficient for the 1-cm
geoid, even for areas with very rough topography and high gravity
variations. The results also show that the omission errors to
gravity are significant even for 1' grid size, at which the
smoothed-out gravity still reaches tens of mGals. The omission
errors to gravity at a 5' grid size peaks above 100mGals,
demonstrating the importance of correction of residual terrain to
gravity observations in data gridding or block mean value
computations. The results are also compared with those based on
Kaula’s rule. While the omission errors based on Kaula’s rule
are 0.5 and 3.0cm for 1' and 5' grid size, respectively, the RMS
values of the omission error in this paper are 0.1 and 1.1cm. The
differences suggest Kaula’s rule may overestimate the power of
the gravity field at the ultra-high frequency band, which renders
the convergence studies of the spherical harmonic series based on
Kaula’s rule questionable.
|
Download (ppt) (2.39 MB)
|
Modeling Airborne Gravimetry with High-Degree Harmonic Expansions
|
Yan Ming Wang
|
Holmes SA
|
YM Wang, XP Li and DR Roman
|
2010/05/07
|
Vienna, Austria
|
European Geosciences Union General Assembly 2010
|
airborne gravity modeling, harmonic expansion
|
Show Abstract
Since its official unveiling at the 2008 General Assembly of the
European Geosciences Union, EGM2008 has demonstrated that
high-degree harmonic expansions constitute a useful and effective
final representation for high-resolution global gravitational
models. However, such expansions also provide a versatile means
of capturing (modeling), inter-comparing, and optimally combining
local and regional high-resolution terrestrial data sets of
different types. Here we present a general recipe for using
high-degree expansions to capture, downward-continue and
assimilate airborne survey data. This approach relies on the
production of two ‘competing’ high-degree expansions. A
first, ‘terrestrial-only’ expansion incorporates EGM2008
globally, and high-resolution terrestrial gravimetry regionally.
This expansion can be used to upward-continue the regional
terrestrial data to the flight level of the airborne survey, such
that the terrestrial gravimetry outside the survey area can be
merged with the airborne data inside the survey area, all at
flight level. Harmonic analysis of this merged data set, also at
flight level, yields a second ‘airborne-augmented’ expansion,
which closely matches the ‘terrestrial-only’ expansion
outside the survey area, but which also closely reproduces the
airborne survey data inside the survey area. Capturing the
airborne and terrestrial data in this way means that
downward-continuation of the airborne data, as well as
spectral/spatial comparison (and ultimate combination) of the
airborne data with the terrestrial (and satellite) data, can all
be achieved through spherical- and ellipsoidal-harmonic synthesis
of these two competing expansions, and their spectral
combination. This general approach is illustrated with a worked
example.
|
Download (pptx) (3.20 MB)
|
GEOID03 in Louisiana and Alaska
|
Yan Ming Wang
|
Yan Ming Wang
|
D Roman
|
2006/04/22
|
Orlando, FL
|
ACSM Annual Conference and Technology Exhibition
|
geoid in Louisiana and Alaska
|
|
Download (ppt) (6.65 MB)
|
Nuts and Bolts of submitting a Digital leveling project to NGS
|
Edward Carlson & Curt Smith
|
Edward Carlson
|
Curt Smith
|
2010/04/20
|
ASCM Anual Conference, Phoenix, AZ
|
Workshop
|
Windesc, Tranlev
|
Show Abstract
The workshop will consists of: 1. General overview digital
leveling - NGS way 2. WINDESC program - with hands on examples 3.
Translev program - with hands on examples 4. LOCUS 5. Project
reports. The goal is at the end of the 8 hours a small leveling
project will be completed. Plus, the workshop will be alot on
hands with examples and problems so everyone will need to have
their own laptop.
|
Download (zip) (150.15 MB)
|
Geodetic Datums of the U.S. Virgin Islands
|
Dave Doyle
|
Dave Doyle
|
|
2006/06/22
|
St. Croix, VI
|
2nd Annual GIS Conference
|
Datums, Virgin Islands
|
|
Download (pdf) (1.51 MB)
|
Datums Seminar, Geodetic Vertical--Part I
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/06/13
|
Menlo Park, CA
|
SBSP Restoration Project
|
geodetic vertical datum GPS geoid height NAVD88
|
Show Abstract
A 2-hour seminar was webcast live and recorded to provide researchers and scientists
working on the (San Francisco) South Bay Salt Pond Restoration Project with a clear
understanding of geodetic vertical and tidal datums in the area. The following website
includes links to the webinar as well as presentation materials and related reports
from SSF Bay studies. http://www.southbayrestoration.org/science/2011-datums-seminar/
|
Download (pptx) (14.72 MB)
|
Datums Seminar, Tidal--Part II
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/06/13
|
Menlo Park, CA
|
SBSP Restoration Project
|
tidal datum SSF Bay
|
Show Abstract
A 2-hour seminar was webcast live and recorded to provide researchers and scientists
working on the (San Francisco) South Bay Salt Pond Restoration Project with a clear
understanding of geodetic vertical and tidal datums in the area. The following website
includes links to the webinar as well as presentation materials and related reports
from SSF Bay studies. http://www.southbayrestoration.org/science/2011-datums-seminar/
|
Download (pptx) (9.72 MB)
|
NGS Updates
|
Marti ikehara
|
Marti Ikehara
|
|
2011/06/15
|
San Rafael, CA
|
CLSA Marin Chapter
|
Reference frame, CORS, 2011 adjustment, HTDP, Subscribe
|
Show Abstract
Reference frame changing for CORS;
Adjustment/Datum tag changing for passive;
CORS what's different?;
Want to keep up?;
HTDP what's different?;
RTN Guidelines;
GC Mapping tools;
Learning Resources
|
Download (pptx) (5.01 MB)
|
NGS Updates
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/06/21
|
Watsonville, CA
|
CLSA Monterey chapter
|
CBL Reference frame HTDP CGAR
|
Show Abstract
CBL Process
CBL Site Characteristics
Adoption of new reference frame for CORS
Subsequent adjustment for passive stations
HTDP
CGAR
Developments of various NGS products
|
Download (pptx) (8.29 MB)
|
Data and Datum-Informed Decision-Making: Understanding Essential Integrated Data Needs for Informing SAGE
|
Juliana Blackwell
|
Juliana Blackwell
|
Galen Scott and Brett Howe
|
2011/06/29
|
Charleston, SC
|
USACE, NOAA and FEMA Systems Approach to Geomorphic Engineering (SAGE) Conference
|
National Ocean Service, overview, NOS 101, Datums, USACE, FEMA, coastal, coastal mapping, senitnel sites, coastal management, shoreline
|
Show Abstract
The U.S. Army Corps of Engineers (USACE) National Oceanic and Atmospheric
Administration (NOAA) and the Federal Emergency Management Agency (FEMA) are in
the early stages of developing a tri-agency initiative entitled SAGE,
which stands for Systems Approach to Geomorphic Engineering. The purpose of
this tri-agency initiative is to pursue and advance a comprehensive view of
shoreline change and to utilize integrated methodologies for coastal landscape
transformation to slow/prevent/mitigate/adapt impacts to coastal communities
from the consequences of climate change. This concept will utilize a holistic
approach in exploring the idea of hybrid engineering, linking "soft"
ecosystem-based approaches with "hard" infrastructure approaches, to develop
innovative techniques and solutions to aid in the adaptation of our changing
coastlines.
This presentation is an overview of National Ocean Service (NOS) contributions
to understanding essential integrated data needs for inporming SAGE. It was
presented by Juliana Blackwell, Director of NOAA's National Geodetic Survey.
|
Download (pptx) (15.00 MB)
|
Progress Toward a Unified Geoid-Based Vertical Datum for North America
|
Dru Smith
|
Dru Smith
|
M Véronneau, D. Avalos-Naranjo, D Roman, Y M Wang and J Huang
|
2011/07/04
|
Melbourne, Australia
|
IUGG
|
Geoid, Vertical Datum
|
Show Abstract
In North America, the last attempt to unify the vertical datum, the North
American Vertical Datum of 1988 (NAVD88), was only adopted by the USA and
Mexico, while Canada elected to remain on the Canadian Geodetic Vertical Datum
of 1928. Furthermore, no attempt to provide a unified datum to the Central
American and Caribbean nations was part of NAVD88. This has led to continued
cross-border height issues on the continent.
Recently, Canada and the United States have initiated policy decisions to
replace their respective datums with new datums realized primarily through GNSS
technology and a gravimetric geoid model. The USA has decided to wait until the
GRAV-D campaign is complete (2022) to make this change. Canada will likely
adopt sooner in 2013, with a possible update in 2022 aligned with the USA.
Although Mexico has not yet adopted a policy of replacing NAVD88, they are
participating in all coordinated efforts towards obtaining a common datum.
Government geodetic agencies in the USA, Canada and Mexico are working toward
the joint computation and adoption of a single gravimetric geoid model covering
all of North America, including all parts of Alaska, Hawaii, Central America and
the Caribbean.
The adopted geoid model will be coordinated with (but may not be identical to)
the IAG's adoption of a unified World Height System. The North American
unified vertical datum will be accessible to all nations in this region through
GNSS technology. This paper discusses progress toward the unification of a
vertical datum for the entire continent.
|
Download (pptx) (4.36 MB)
|
Towards an integrated model of deformation along the western margin of North America
|
Chris Pearson
|
Chris Pearson
|
Richard Snay, Robert McCaffrey
|
2011/07/02
|
Melbourne AU
|
IUGG
|
HTDP crustal deformation
|
Show Abstract
We have developed a block model of tectonic deformation of North America west of
longitude 100° W and between latitudes 30°N and 49°N. NOAA's National
Geodetic Survey (NGS) is in the process of incorporating this model into
version 3.1 of the horizontal time dependent positioning (HTDP) software
tentatively scheduled for release in early 2011. By estimating the horizontal
linear velocity for any point on the ground, HTDP enables surveyors and others
to update (or backdate) positional coordinates measured on one date to
corresponding coordinates that would have been measured on another date. The
model consists of 59 crustal blocks with 46 independent rotation poles and 38
independent strain rate tensors. The model also includes elastic coupling
coefficients on faults that bound adjacent blocks. NGS recently updated
estimates for model parameters by using 6,063 GPS-derived velocity vectors
(including vectors from the 2009 Plate Boundary Observatory (PBO) solution and
the NGS Multiyear CORS) and 330 geological measurements of fault slip and/or
fault orientation. In general, the fault slip rates and the interseismic
coupling coefficients are consistent with the results of previous studies;
however, because of the comprehensive nature of this model, we are able to
quantitatively map deformation rates over the entire deforming region. Slip
rates on the faults range from over 30 mm/yr for the Cascadia subduction zone
and parts of the San Andreas system to near zero for faults adjacent to stable
North America. In particular, our study confirms very low deformation rates
across eastern Nevada and western Utah.
|
Download (zip) (6.57 MB)
|
Error analysis of the NGS gravity database
|
YM Wang
|
J Saleh
|
YM Wang, X Li, D Roman and D Smith
|
2011/07/04
|
Melbourne, Australia
|
IUGG2011
|
Gravity and geoid errors
|
Show Abstract
Are the National Geodetic Survey's surface gravity data sufficient for
supporting a 1cm-accurate geoid? We evaluate the errors of these surface data
and their effect on the geoid. Long wavelength errors are derived by comparison
to synthetic GRACE gravity and high-frequency errors by crossover analysis and
K-Nearest-Neighbor predictions.
|
Download (ppt) (3.20 MB)
|
Upcoming Changes to the National Spatial Reference System
|
Dave Minkel
|
Dave Minkel
|
|
2011/07/08
|
San Diego, CA
|
ACSM/ESRI Survey Summit
|
NSRS, NAD 83, datums
|
Show Abstract
Discussion of the new geometric and vertical datums NGS intends to deliver on or
about 2012.
|
Download (ppt) (10.63 MB)
|
GPS Positioning Performance from Algorithm Advances in the Network Version of OPUS
|
Neil D. Weston
|
Neil D. Weston
|
Jim R. Ray
|
2011/04/08
|
Vienna, Austria
|
European Geosciences Union 2011 General Assembly
|
OPUS, CORS, Reference Frames, Positioning
|
|
Download (ppt) (0.87 MB)
|
Achieving great heights with NOAA tools: VDatum and LOCUS
|
Michael Dennis
|
Michael Dennis
|
|
2011/07/08
|
San Diego, CA
|
ACSM/Esri Survey Summit
|
VDatum, LOCUS, Heights, Vertical datums, Datum transformations, Geodetic leveling
|
Show Abstract
Heights (elevations) are complicated. Some are reckoned as straight lines
perpendicular to a reference surface (ellipsoid heights), some are curved lines
parallel to gravity at every point (orthometric heights), and some 'heights'
have no geometric meaning at all yet tell you where water will go (dynamic
heights). The datum to which heights refer can be a mathematical
ellipsoid surface, which in turn is referenced to one of several different
global or regional frames. It can be a vertical datum defined by a geodetic
leveling network, or by a geoid, a gravitational equipotential surface
more-or-less representing global mean sea level. It can be defined by a
particular tide gage as local mean sea level, or mean high water, or mean lower
low water, etc. Adding to the complexity, heights are measured by a wide
variety of equipment, each with corrections, models, and methodologies that
yield particular types of heights referenced to various datums over a broad
range of accuracies.
NOAA has created two tools, VDatum and LOCUS, to help geospatial professionals
make better use of height data and measurements. VDatum is free software
developed jointly by NOAAs National Geodetic Survey (NGS), Office of Coast
Survey (OCS), and Center for Operational Oceanographic Products and Services
(CO-OPS). It vertically transforms geospatial data among a variety of tidal,
orthometric, dynamic, and ellipsoidal height systems. This allows users to
convert their data from different vertical (and horizontal) references into a
common system and enables the fusion of diverse geospatial data into a uniform
reference system. For example, VDatum can be used to combine a bathymetric
survey referenced to a local tidal datum with a digital elevation model based on
the North American Vertical Datum of 1988 (NAVD 88) into a single seamless
surface model.
LOCUS (Leveling Online Calculations User Service) is a free Internet-based NGS
service that checks, corrects, and adjusts leveling data submitted by users and
provides heights with respect to published NGS vertical control.
Philosophically, it is similar to the popular NGS Online Positioning User
Service (OPUS) used for GPS data. As with OPUS, the intent is to make it as
simple as possible for users to get correctly adjusted heights by uploading
their leveling data via the Internet and immediately receiving results. For
example, if a user wants to level with respect to NGS NAVD 88 benchmarks, LOCUS
will apply the appropriate corrections (including the gravity model) to convert
the observed leveled heights differences to NAVD 88 orthometric heights.
Whether combining existing vertical datasets from a variety of sources (VDatum)
or correcting and adjusting precise vertical measurements (LOCUS), NOAA has
developed tools that will assist users in achieving great heights.
|
Download (pptx) (24.24 MB)
|
A New & Improved National Spatial Reference System
|
Michael Dennis
|
Michael Dennis
|
|
2011/07/11
|
San Diego, CA
|
FGCS meeting and ACSM/Esri Survey Summit
|
NAD 83(2011) epoch 2010.00, Multi-Year CORS Solution, National Adjustment of 2011
|
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Download (pptx) (5.58 MB)
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Improved Geoid Height Models from Supplemental Data on Bench Marks
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Gerald L. Mader
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Daniel R. Roman
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2011/07/10
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San Diego Convention Center, San Diego CA
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The ACSM Annual Conference
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Geoid, Geodesy, GPS, GNSS, OPS
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Show Abstract
This presentation follows previous talks that focused on outreach and education
of surveyors. It is designed to update surveyors on the latest research related
to the development of geoid height models as tools for datum transformation
between NAD 83 and NAVD 88. All previous geoid height models have relied upon
control data existent in the National Geodetic Survey Integrated Database
(NGSIDB) to develop the conversion surface between the datums. In GEOID09,
nearly 20,000 such points were available. However, about half of these points
were located in only four of the lower 48 states. Most of the nearly 500,000
bench marks that exist in the NGSIDB have never been occupied with a GPS
receiver. Hence, the bulk of the points are unused in determining the conversion
surface. Given the disparate distribution of the few points that were occupied
with GPS and the desire to supplement these in sparsely covered regions,
alternative control data is desirable. The Online Positioning User Service
Database (OPUS-DB) is where surveyors have the option of storing their
observations for the use of others. Many of these marks were obtained on leveled
bench marks. In November of 2010, there were about 422 points pulled from
OPUS-DB with 285 representing new bench marks and providing supplemental control
not previously available. These points are spread across the country and provide
significant improvement in many regions, especially the sparsely covered western
states. The errors resulting from interpolation over hundreds of kilometers can
result in dm to multi-dm level errors in the resulting geoid height model. The
OPUS-DB determined points then supplement the existing coverage from the NGSIDB.
Many of these gaps were filled, and this reduced the interpolation error for
those regions. More over, a campaign can be put in place to identify the sparse
regions and likely candidate bench marks to target and fill these gaps. State
Advisers/Coordinators and various state surveying groups have begun to organize
efforts to collect GPS observations on the previously unoccupied bench marks and
store them in OPUS-DB. For example, the distribution of control data from the
NGSIDB points in Arizona have been examined, and that State Adviser has made
known regions that require supplemental information in the OPUS-DB. These points
will be examined as they become available and a determination made as to whether
to incorporate them into future geoid height models. Preliminary analysis does
indicate that there is some slight inferiority to the quality of OPUS-DB data in
that the apparent error signal (noise) is generally about double that of NGSIDB
data. However, noisier data can be accounted for using least squares collocation
- missing signal due to gaps cannot be easily overcome. Use of OPUS-DB to
supplement coverage shows great promise as a means of readily collecting
information without the need for following the Bluebook, but doing so where it
can provide the most improvement to future geoid height models for datum
transformations.
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Download (pptx) (17.49 MB)
|
Comparison of Extensive Aerogravity Surveys to EGM's
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Daniel R. Roman
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Daniel R. Roman
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Simon A. Holmes, Sandra A. Preaux, Theresa M. Diehl, and Vicki Childers
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2011/07/04
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Melbourne, Australia
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IUGG 2011
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Session G06S3: World Height System
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Show Abstract
Extensive airborne gravity surveys have been conducted as a part of the Gravity
for the Redefinition of the American Vertical Datum (GRAV-D) project by the U.S.
National Geodetic Survey. The intent is to capture the mid-wavelengths of the
gravity field over all of the U.S.A. GRAV-D bridges the gap between long
wavelengths determined by satellite gravity missions and shorter wavelengths
determined from surface observations as well as forward-modelling of surface
density and elevation models. The GRAV-D surveys were collected in 10-km spaced
profiles covering 400-500 km patches, which are adequate in scale to compare to
Earth Gravity Models through about degree 90. Initial comparisons with EGM2008
revealed no detectable slope across these patches, supporting the idea that no
significant long wavelength differences exist between the aerogravity and the
GRACE satellite data on which EGM2008 is based. However, only half the signal in
EGM2008 is from satellite data at degree 95; indicating that a strict comparison
of GRAV-D to the GRACE gravity field is less than exact. With the release of the
GOCE data, higher resolution EGM's based entirely upon satellite gravity models
make this comparison a more direct assessment of the long to intermediate
quality of the aerogravity. This will enable generation of an EGM with 20 km
resolution (approximately degree 2000). In turn, this model will be combined
with the existing terrestrial data to build a higher resolution model towards
defining a cm-level accurate gravimetric geoid model to be used as a new
vertical datum for the United States.
|
Download (ppt) (4.36 MB)
|
OPUS-Database: Supplemental Data for Better Datum Conversion Models
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Michael Dennis
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Daniel R. Roman
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Neil D. Weston
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2011/05/20
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Marrakech, Morocco
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F.I.G. Working Week
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OPUS, GPSBM, Hybrid Geoid
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Show Abstract
NOAA's National Geodetic Survey (NGS) is responsible for maintaining the
National Spatial Reference System. This includes the national geometric and
geopotential datums, which are the North American Datum of 1983 (NAD 83) and the
North American Vertical Datum of 1988 (NAVD 88), respectively. For NAVD 88,
Helmert orthometric heights were defined in a block adjustment of over 500,000
geopotential differences at bench marks. As an alternative to leveling from
established bench marks, NGS provides geoid height models such as GEOID09 (Roman
et al. 2011) that transform between NAD 83 and NAVD 88. This provides the ease
of calculating your position with GPS but yields more practical orthometric
heights. To develop such models requires that both the GPS-derived ellipsoidal
and leveling-derived orthometric heights on Bench Marks (GPSBM's) be known.
Because of the requirement for both heights on a bench mark, the pool of control
points is much smaller (only about 18,000) and not very equitably distributed
(with potential dm-level interpolation errors). This paucity of points is driven
by the rigorous processes ("Bluebooking") required to enter data into the NGS
Integrated Database (NGSIDB). To mitigate this, the Online Positioning User
Service Database (OPUS-DB) was explored as a source for supplemental data. This
nascent database is rapidly being accepted by the broader surveying community
and can even be used to target significantly deficient areas. A pull of OPUS-DB
in November 2010 yielded 422 points. While this number is small in comparison to
the overall NGSIDB data, the potential for growth is significant. These points
fell into three categories: (1) 80 that were common to both databases and were
used in making GEOID09, (2) 57 that were common to both but not used in making
GEOID09, and (3) 285 with new geometric observations for points not previously
observed with GPS (i.e., new control points). Residual values were formed by
removing the same geoid and orthometric heights from ellipsoid heights obtained
from NGSIDB and OPUS-IDB. Smaller values imply a better fit and less noise. For
the first group, OPUS-DB was noisier (SD 0.031 m (one sigma)) than NGSIDB (SD
0.015 m (one sigma)). For the second group, OPUS-DB was less noisy (0.037 m
(one sigma)) than the NGSIDB (0.043 m (one sigma)). For the last group, only
OPUS-DB data were available and they were a little worse (0.047 m (one sigma))
than before. This is consistent with the level of agreement seen when forming
residuals between ellipsoidal heights from NGSIDB and OPUS-DB in groups 1 and 2
(SD of 0.028 m and 0.044 m (one sigma), respectively). Overall, OPUS-DB
demonstrated very good agreement with more rigorously determined NGSIDB data,
provided expanded coverage into regions with poor coverage, and demonstrated a
significant potential for use in future geoid modeling.
|
Download (pptx) (2.10 MB)
|
Part 1: Tools to Obtain Geodetic Control
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John Ellingson
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John Ellingson
|
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2011/07/18
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Chicago, IL
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Coastal Zone 11 Conference
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Tools, DSWorld, OPUS, CORS
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Show Abstract
COOL GEODETIC RESOURCES FOR YOUR PROJECT
Nearly every effort that involves planning, protecting, or monitoring our
Nation's coasts and Great Lakes relies on knowing or establishing geographic
positions and elevations of objects or locations-of-interest in the project
area. A recommended method to accomplish that is to reference the project to
the well-known and respected reference system, the National Spatial Reference
System (NSRS). The NSRS, defined and maintained by NOAA's National Geodetic
Survey (NGS), is a consistent National coordinate system that specifies
latitude, longitude, height, scale, gravity, and shoreline throughout the
Nation. It is NGS' mission to develop and provide access to the NSRS "to
meet our Nation's economic, social, and environmental needs." This panel
discussion will improve attendees' knowledge of methods they can use to obtain
and use geodetic control. It will also update the audience about NGS' goals
for improving the definition and delivery of horizontal and vertical datums.
This session will inform the audience about new methods developed by NGS to
facilitate easy access to data for approximately 1.5 million geodetic control
marks that exist in the NGS database, with a brief description of software tools
such as DSWorld, which works with GoogleEarth. It will inform the audience
about the latest Online Positioning User Service� (OPUS) utilities, which
can be used to establish, or check, coordinates and elevations for projects
referenced to the NSRS, enabling users to complete their work more efficiently.
Also to be covered will be information about resources that are available to
anyone needing assistance with locating, using, or producing geodetic
information about their projects. Attendees will learn about NGS' Geodetic
Advisors, who are located around the United States with the purpose of educating
and assisting people in utilizing NGS products and services in their projects or
applications.
|
Download (ppt) (7.06 MB)
|
Part 2: Geodetic & Tidal Datums and Using VDatum
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/07/18
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Chicago, IL
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Coastal Zone '11 Conference
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VDATUM tidal vertical tools
|
Show Abstract
Nearly every effort that involves planning, protecting, or monitoring our
Nation's coasts and Great Lakes relies on knowing or establishing geographic
positions and elevations of objects or locations-of-interest in the project
area. A recommended method to accomplish that is to reference the project to
the well-known and respected reference system, the National Spatial Reference
System (NSRS). The NSRS, defined and maintained by NOAA's National Geodetic
Survey (NGS), is a consistent National coordinate system that specifies
latitude, longitude, height, scale, gravity, and shoreline throughout the
Nation. It is NGS' mission to develop and provide access to the NSRS "to
meet our Nation's economic, social, and environmental needs." This panel
discussion will improve attendees' knowledge of methods they can use to obtain
and use geodetic control. It will also update the audience about NGS' goals
for improving the definition and delivery of horizontal and vertical datums.
This session will discuss the relationship of geodetic and tidal vertical
datums, and the necessity of understanding how to describe the relationship.
The software program VDATUM was developed jointly by NOAA's NGS, Office of
Coast Survey (OCS), and Center for Operational Oceanographic Products and
Services (CO-OPS) to enable users to easily transform data from various vertical
and/or horizontal datums into another datum for a location that is on the
tidally influenced coastline. The input data can be elevations or (bathymetric)
soundings, and batch files can be submitted. A brief tutorial will illustrate
how to use the software, the accuracy associated with the conversions, and some
of the common errors that users make.
|
Download (pptx) (11.90 MB)
|
Part 3: International Great Lakes Datum (IGLD) Overview
|
Stephen Gill
|
Stephen Gill
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Dru Smith, Jeff Oyler
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2011/07/18
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Chicago, IL
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Coastal Zone 11 Conference
|
Dynamic Height, IGLD, COOPS
|
Show Abstract
COOL GEODETIC RESOURCES FOR YOUR PROJECT
Nearly every effort that involves planning, protecting, or monitoring our
Nation's coasts and Great Lakes relies on knowing or establishing geographic
positions and elevations of objects or locations-of-interest in the project
area. A recommended method to accomplish that is to reference the project to
the well-known and respected reference system, the National Spatial Reference
System (NSRS). The NSRS, defined and maintained by NOAA's National Geodetic
Survey (NGS), is a consistent National coordinate system that specifies
latitude, longitude, height, scale, gravity, and shoreline throughout the
Nation. It is NGS' mission to develop and provide access to the NSRS "to
meet our Nation's economic, social, and environmental needs." This panel
discussion will improve attendees' knowledge of methods they can use to obtain
and use geodetic control. It will also update the audience about NGS' goals
for improving the definition and delivery of horizontal and vertical datums.
This session will provide information about the efforts underway to produce a
new International Great Lakes Datum (IGLD), with a goal for release in
2015. Being discussed are the reasons why a new IGLD is desirable, the data
collection and analysis effort to update the datum, and examples of the impact
of the new datum on the Great Lakes region. The international GPS campaign
related to the new IGLD, completed in the Great Lakes region in 2010 by Natural
Resources Canada's Geodetic Survey Division and NOAA's NGS, will be
described.
|
Download (ppt) (1.66 MB)
|
Better Positions and Improved Access to the National Spatial Reference System
|
Michael L Dennis
|
Michael L Dennis
|
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2011/08/19
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Silver Spring, MD
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NOAA's National Height Modernization Program Partner Meeting
|
NAD 83(2011) epoch 2010.00, Multi-Year CORS Solution, National Adjustment of 2011, NGS Datasheet
|
|
Download (pptx) (4.95 MB)
|
GNSS Absolute Antenna Calibration at the National Geodetic Survey
|
Andria Bilich
|
Andria Bilich
|
Gerald Mader
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2011/08/22
|
Silver Spring, MD
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NGS Brownbag
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antenna calibration, absolute calibration
|
|
Download (pptx) (4.96 MB)
|
FGCS Update to the FGDC
|
Ronnie Taylor
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Juliana Blackwell
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Ronnie Taylor, Jeremy McHugh
|
2011/09/20
|
401 9th St NW, Washington, DC
|
Federal Geographic Data Committee, Coordination Group Meeting
|
Geodetic Control, FGDC, FGCS
|
|
Download (pptx) (0.48 MB)
|
Physical Models Used (and Not Used) in GNSS Data Processing
|
Dr. Mark Schenewerk
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Dr. Mark Schenewerk
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2011/11/03
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Casper, WY
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Professional Land Surveyors of Wyoming Technical Sesssion
|
GNSS processing models
|
Show Abstract
Global Navigation Satellite System (GNSS) data processing requires many
different numerical models to describe the physical processes affecting the
positions of the satellites and points on the ground as well as the propagation
of the GNSS signals from the satellites to the user. Some of these models are
commonly known: satellite orbits, tropo and antenna corrections are examples
from this group. Others are probably less well known: phase wrapping,
atmospheric gradients and solid Earth tides are examples from this group. In
this presentation, many of these models will be described with a focus on
broader conceptual understandings rather than detailed technical descriptions.
Real examples from data processing will be included whenever possible thereby
adding the magnitudes of these physical processes to your understanding. The
ultimate goal is to give you a better awareness of what your GNSS processing
software should be doing to give you the accuracy necessary for your needs.
|
Download (pptx) (10.04 MB)
|
New Developments at the National Geodetic Survey
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
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2011/11/03
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Casper, WY
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Professional Land Surveyors of Wyoming Technical Sesssion
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NGS CORS OPUS "height modernization" datasheet GRAV-D geoid
|
Show Abstract
The National Geodetic Survey, NGS, traces its history back to the early
1800's. Although its mission has adapted to changing times and technology,
this two hundred year history is alive in the NGS today. Using an overview of
the NGS as an organizing framework, some NGS activities of particular interest
to the surveying communities will be highlighted. Among the activities
highlighted in this presentation are: improved coordinates for the CORS and a
large subset of the passive mark networks (NAD 83(2011) and NA2011); the related
work to define a new hybrid geoid model providing improved consistency with
these new coordinates and velocities (GEOID12); the Gravity for the Redefinition
of the American Vertical Datum (GRAV-D) mission to create a snapshot of
gravity across the United States in unparalleled detail; the Online Positioning
User Service (OPUS) providing virtually hands-off, high-accuracy GNSS data
processing; and the creation of guidelines to help real-time network providers
more rigorously tie their networks to the global and national datums.
|
Download (pptx) (42.57 MB)
|
New Developments for OPUS
|
Dr. Mark Schenewerk
|
Dr. Mark Schenewerk
|
|
2011/11/04
|
Casper, WY
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Professional Land Surveyors of Wyoming Technical Sesssion
|
OPUS
|
Show Abstract
The Online Positioning User Service (OPUS) is a National Geodetic Survey tool
that provides you with a National Spatial Reference System coordinate via email
in seconds using your own GPS data file. Several notable enhancements have been
implemented or are pending for OPUS. OPUS-Projects is a new option providing
tools to handle GPS projects involving several sites occupied over several days.
OPUS-Projects includes project visualization and management tools, enhanced
processing options, and one click publishing for an entire project. OPUS
is testing a new static processing strategy. By including more CORS at various
distances and more sophisticated geophysical models, this new strategy improves
the reliability of the results without sacrificing flexibility. OPUS-RS also
offers a new CORS selection strategy which improves reliability and expands the
regions in which this is a viable processing option. Underlying these
enhancements are new CORS coordinates derived from a recently completed global
GNSS network solution. This solution provides improved coordinates for all
included CORS that are consistent with recognized reference systems such as the
ITRF2008. These and other new developments will be described.
|
Download (pptx) (13.78 MB)
|
WHY DOES THE IGS CARE ABOUT EOPs?
|
Jim Ray
|
Jim Ray
|
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2011/11/17
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Springfield, VA
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NGA Future EOP Prediction Workshop
|
Earth orientation, IGS, GPS orbits
|
|
Download (ppt) (1.36 MB)
|
Improvements to the NSRS
|
Marti Ikehara
|
Marti Ikehara
|
|
2011/11/30
|
Webinar
|
CLSA
|
CORS Coordinates Velocities NAD83(2011) DSFormat DSWorld
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Show Abstract
The California Geodetic Advisor will discuss: NEW Coordinates and epoch for the
NSRS CORS that were published on Sept 6; In-progress adjustment of nearly 80K
passive stations nationwide; Development of GEOID12 based on new ellipsoid
heights; Changes to the Datasheet format/content; and DSWorld: a GoogleEarth
mapping tool and more.
|
Download (ppt) (5.61 MB)
|
Initial Results of the Geoid Slope Validation Survey of 2011
|
Dru Smith
|
Dru Smith
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Simon Holmes, Xiaopeng Li, Yan Wang, Malcolm Archer-Shee, Ajit Singh, Cliff Middleton, Daniel Winester, Dan Roman, Beat Bürki, Sébastien Guillaume
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2011/12/09
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San Francisco, CA
|
AGU
|
GSVS11, Geoid, Airborne Gravity
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Show Abstract
The National Oceanic and Atmospheric Administration's (NOAA), National
Geodetic Survey (NGS) has embarked on a ten year project called GRAV-D (Gravity
for the Redefinition of the American Vertical Datum). The purpose of this
project is to replace the current official vertical datum, NAVD 88 (the North
American Vertical Datum of 1988) with a geopotential reference system based on a
new survey of the gravity field and a gravimetric geoid.
As part of GRAV-D, NGS plans to execute a set of "geoid validation surveys"
at various locations of the country. These will be surveys designed to
independently measure the geoid to provide a check against both the data and
theory used to create the final gravimetric geoid which will be used in the
geopotential reference system.
The first of these surveys, known as the Geoid Slope Validation Survey of 2011
(GSVS11) was executed between July and October, 2011 in the central region of
Texas. The survey took place over a 325 kilometer line running more or less
north-south from Austin to Corpus Christi, Texas. Measurements were taken at
218 marks (one per mile) and included static GPS, RTN GPS, geodetic leveling,
astro-geodetic deflections of the vertical using the Swiss DIADEM camera,
absolute gravity, gravity gradients and LIDAR. This region was chosen for many
factors including the availability of GRAV-D airborne gravity over the area, its
relatively low elevation (220 meter orthometric height max), its geoid slope
(about 130 cm over 300 km), lack of significant topographic relief, lack of
large forestation, availability of good roads, clarity of weather and lack of
large water crossings.
This talk will outline the initial results of the survey, specifically the
comparison of various geoid slopes over this region: gravimetric geoid models
(with and without airborne gravity), minimally constrained GPS and leveling and
from astro-geodetic deflections of the vertical.
|
Download (pptx) (4.85 MB)
|
Consistency of Crustal Loading Signals Derived from Models & GPS: Inferences for GPS Positioning Errors
|
Jim Ray
|
Jim Ray
|
Xavier Collilieux, Paul Rebischung, Tonie van Dam, Zuheir Altamimi
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2011/12/09
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San Francisco
|
American Geophysical Union
|
GPS, accuracy, crustal loads, positioning
|
Show Abstract
Consistency of Crustal Loading Signals Derived from Models and GPS:
Inferences for GPS Positioning Errors
After applying corrections for surface load displacements to a set of
station position time series determined using the Global Positioning System
(GPS), we are able to infer precise error floors for the determinations of
weekly dN, dE, and dU components. The load corrections are a combination of
NCEP atmosphere, ECCO non-tidal ocean, and LDAS surface water models, after
detrending and averaging to the middle of each GPS week. These load
corrections have been applied to the most current station time series from
the International GNSS Service (IGS) for a global set of 706 stations, each
having more than 100 weekly observations. The stacking of the weekly IGS
frame solutions has taken utmost care to minimize aliasing of local load
signals into the frame parameters to ensure the most reliable time series
of individual station motions. For the first time, dN and dE horizontal
components have been considered together with the height (dU) variations.
By examining the distributions of annual amplitudes versus WRMS scatters for
all 706 stations and all three local components, we find an empirical error
floor of about 0.65, 0.7, and 2.2 mm for weekly dN, dE, and dU. Only the very
best performing GPS stations approach these floors. Most stations have larger
scatters due to other non-load errors. These global error floors have been
verified by studying differences for a subset of 119 station pairs located
within 25 km of each other. Of these, 19 pairs share a common antenna, which
permits an estimate of the fundamental electronic noise in the GPS estimates:
0.4, 0.4, and 1.3 mm for dN, dE, and dU. The remaining 100 close pairs that
do not share an antenna include this noise component as well as errors due
to multipath, equipment differences, data modeling, etc, but not due to
loading or direct orbit effects since those are removed by the differencing.
The WRMS dN, dE, and dU differences for these close pairs imply station error
floors of 0.8, 0.9, and 2.1 mm, respectively, almost the same as the error
floors inferred from the global results where orbit errors should be fully
expressed. This match implies that GPS orbit errors are only a minor part
of the IGS weekly position uncertainties. A similar comparison for periodic
signals implies that about a third of the GPS draconitic harmonics probably
arise from sources local to the stations whereas the remaining two-thirds
comes from orbital effects.
|
Download (ppt) (1.68 MB)
|
SUBDAILY ALIAS AND DRACONITIC ERRORS IN THE IGS ORBITS
|
Jake Griffiths
|
Jake Griffiths
|
Jim Ray
|
2011/12/09
|
San Francisco
|
American Geophysical Union
|
GPS orbits, accuracy, subdaily EOP tides, draconitic period
|
Show Abstract
Subdaily Alias and Draconitic Errors in the IGS Orbits
Harmonic signals with a fundamental period near the GPS draconitic year
(351.2 d) and overtones up to the 8th multiple have been observed in the
power spectra of nearly all products of the International GNSS Service
(IGS), including station position time series [Ray et al., 2008;
Collilieux et al., 2007; Santamaria-Gomez et al., 2011], apparent
geocenter motions [Hugentobler et al., 2008], and orbit jumps between
successive days and midnight discontinuities in Earth orientation
parameter (EOP) rates [Ray and Griffiths, 2009]. Ray et al. [2008]
suggested two mechanisms for the harmonics: mismodeling of orbit dynamics
and aliasing of near-sidereal local station multipath effects. King and
Watson [2010] have studied the propagation of local multipath errors into
draconitic position variations, but orbit-related processes have been less
well examined.
Here we elaborate our earlier analysis of GPS orbit jumps [Griffiths and
Ray, 2009; Gendt et al., 2010] where we observed some draconitic features
as well as prominent spectral bands near 29, 14, 9, and 7 d periods. Finer
structures within the sub-seasonal bands fall close to the expected alias
frequencies of subdaily EOP tide lines but do not coincide precisely. While
once-per-rev empirical orbit parameters should strongly absorb any subdaily
EOP tide errors due to near-resonance of their respective periods, the
observed differences require explanation. This has been done by simulating
known EOP tidal errors and checking their impact on a long series of daily
GPS orbits. Indeed, simulated tidal aliases are found to be very similar to
the observed orbital features in the sub-seasonal bands. Moreover and
unexpectedly, some low draconitic harmonics were also stimulated,
potentially a source for the widespread errors in most IGS products.
|
Download (ppt) (1.79 MB)
|
Real Time Positioning - Best Methods for the Field
|
Bill Henning
|
Bill Henning
|
|
2011/11/09
|
Silver Spring, MD
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webinar
|
Real Time Positioning, Datums
|
Show Abstract
How do we achieve confidence with our Real Time (RT) work?
What pitfalls should we avoid?
Are there guidelines to follow to help us with our procedures?
How accurate are the Real Time Networks?
Should I be using Glonass?
Those are just some of the common questions surveyors, engineers and other
geospatial professionals ask when they go to the field to obtain RT GNSS
positional coordinates. Because so much of RT GNSS positioning is transparent to
the user and is entirely dependent on the field technician to bring back good
data, it is incumbent on that technician to follow correct procedures and
certain criteria to ensure a successful campaign. This webinar will show the
recommended specific criteria to achieve 4 different grades of precision at the
95% confidence level, and will present the critical areas that can affect our RT
data collection.
|
Download (pptx) (19.18 MB)
|
Evaluation of GPS Orbit Prediction Strategies for the IGS Ultra-rapid Products
|
Kevin Choi
|
Kevin Choi
|
Tae-Suk Bae, Jake Griffiths, Jim Ray
|
2011/12/08
|
San Francisco
|
American Geophysical Union
|
orbits, GPS, prediction, IGS, Ultra-rapid
|
Show Abstract
Evaluation of GPS Orbit Prediction Strategies for the IGS Ultra-rapid
Products
To serve real-time and near real-time users, the International GNSS Service
(IGS) produces Ultra-rapid GPS & GLONASS orbit product updates every 6 hr.
Each is composed of 24 hr of observed orbits, with an initial latency of 3 hr,
together with propagated orbits for the next 24 hr. We have studied how the
orbit prediction performance varies as a function of the arc length of the
fitted observed orbits and the parameterization strategy used to estimate
empirical solar radiation pressure (SRP) effects. To focus on the dynamical
aspects of the problem, nearly ideal conditions have been adopted by using
IGS Rapid orbits as observations and known Earth orientation parameters
(EOPs). Performance was gauged by comparison with Rapid orbits as truth by
examining WRMS and median orbit differences over the first 6 hr and the full
24 hr prediction intervals, as well as the stability of the Helmert alignment
parameters. Note that the actual IGS Ultra-rapid accuracy is limited mostly
by rotational instabilities, especially about the Z axis due to errors in
near real-time and predicted UT1 values.
We found that observed arc lengths of 40 to 44 hr produce the most stable and
accurate predictions during 2010. Two versions of the extended SRP orbit model
by the Centre for Orbit Determination in Europe (CODE) were tested. Adjusting
all 9 SRPs (offsets plus once-per-rev sines and cosines in each D,Y,B
component) for each satellite shows smaller mean subdaily, scale, and origin
translation differences. On the other hand, when the 4 once-per-rev SRPs in
the D and Y directions are held fixed, then smaller, more stable rotational
differences are obtained. A combined strategy of rotationally aligning the
9-SRP results to the 5-SRP frame should give optimal predictions with about
15 mm mean WRMS over the first 6 hr and 35 mm over 24 hr. Actual Ultra-rapid
performance will be degraded due to larger errors in the available near
real-time observed orbits and EOP predictions.
|
Download (pdf) (3.76 MB)
|
GNSS Absolute Antenna Calibration at the National Geodetic Survey
|
Andria Bilich
|
Andria Bilich
|
Gerald Mader, Charles Geoghegan
|
2011/12/07
|
San Francisco, CA
|
American Geophysical Union Fall Meeting
|
GPS, antenna calibration, absolute calibration
|
Show Abstract
Geodetic GNSS applications routinely demand millimeter precision and extremely
high levels of accuracy. To achieve these accuracies, measurement and instrument
biases at the centimeter to millimeter level must be understood. One of these
biases is the antenna phase center, the apparent point of signal reception for a
GNSS antenna. It has been well established that phase center patterns differ
between antenna models and manufacturers; additional research suggests that the
addition of a radome or the choice of antenna mount can significantly alter
those a priori phase center patterns. For the more demanding GNSS positioning
applications and especially in cases of mixed-antenna networks, it is all the
more important to know antenna phase center variations as a function of both
elevation and azimuth in the antenna reference frame and incorporate these
models into analysis software.
To help meet the needs of the high-precision GNSS community, the National
Geodetic Survey (NGS) now operates an absolute antenna calibration facility.
Located in Corbin, Virginia, this facility uses field measurements and actual
GNSS satellite signals to quantitatively determine the carrier phase
advance/delay introduced by the antenna element. The NGS facility was built to
serve traditional NGS constituents such as the surveying and geodesy
communities, however calibration services are open and available to all GNSS
users as the calibration schedule permits. All phase center patterns computed
by this facility will be publicly available and disseminated in both the ANTEX
and NGS formats.
We describe the NGS calibration facility, and discuss the observation models and
strategy currently used to generate NGS absolute calibrations. We demonstrate
that NGS absolute phase center variation (PCV) patterns are consistent with
published values determined by other absolute antenna calibration facilities,
and compare absolute calibrations to the traditional NGS relative calibrations.
|
Download (pdf) (1.68 MB)
|
Snow Depth with GPS: Case Study from Minnesota 2010-2011
|
Andria Bilich
|
Andria Bilich
|
Andrew G Slater, Kristine M Larson
|
2011/12/07
|
San Francisco, CA
|
American Geophysical Union Fall Meeting
|
GPS, remote sensing, snow depth, multipath
|
Show Abstract
Although originally designed to enable accurate positioning and time transfer,
the Global Positioning System (GPS) has also proved useful for remote sensing
applications. In this study, GPS signals are used to measure snow depth via GPS
interferometric reflectometry (GPS-IR). In GPS-IR, a GPS antenna receives the
desired direct signal as well as an indirect signal which reflects off of the
ground or snow surface. These two signals interfere, and the composite signal
recorded by the GPS receiver can be post-processed to yield the distance between
the antenna and the reflecting surface, that is, distance to the snow surface.
We present the results of a new snow depth product for the state of Minnesota
over the winter of 2010-2011. Although single-station examples of GPS snow
depth measurements can be found in the literature, this is one of the first
studies to compute GPS snow depth over a large regional-scale network. We chose
Minnesota because the state Department of Transportation runs a network of
continuously operating reference stations (CORS) with many desired
characteristics: freely available data, good GPS station distribution with good
proximity to COOP weather stations, GPS stations located adjacent to farm fields
with few sky obstructions, and receiver models known to have sufficient data
quality for GPS-IR.
GPS-IR with CORS has many advantages over traditional snow depth measurements.
First, because we leverage existing CORS, no new equipment installations are
required and data are freely available via the Internet. Second, GPS-IR with
CORS measures a large area, approximately 100 m2 around the station and 20 m2
per satellite.
We present snow depth results for over 30 GPS stations distributed across the
state. We compare the GPS-IR snow depth product to COOP observations and SNODAS
modeled estimates. GPS-IR snow depth is one of the few independent data sources
available for assessment of SNODAS. Ideally snow depth via GPS-IR will be
available for ingestion into operational systems such as NOAA-NWS streamflow,
weather and climate forecast systems at other locations across the US in the not
too distant future.
|
Download (pdf) (1.12 MB)
|
Modernization of the National Spatial Reference System
|
Dan Martin
|
Dan Martin
|
|
2011/09/23
|
Cape Cod, MA
|
MALSCE Annual Conference
|
NSRS, 10 year plan, new datums
|
Show Abstract
As part of the National Geodetic Survey's 10 year plan for the modernization
of the National Spatial Reference System (NSRS), entirely new horizontal and
vertical datums will be developed to replace the existing NAD 83 and NAVD 88.
The changes in these datums will have a significant impact on the users of
geodetic data nation wide. This presentation will describe the existing
components of NSRS and the rational for the need to adopt new reference frames.
|
Download (ppt) (18.32 MB)
|
Modernization of the National Spatial Reference System
|
Dan Martin
|
Dan Martin
|
|
2011/11/18
|
Providence, RI
|
RISPLS Annual Conference
|
NSRS, 10 year plan, new datums
|
Show Abstract
As part of the National Geodetic Survey's 10 year plan for the modernization
of the National Spatial Reference System (NSRS), entirely new horizontal and
vertical datums will be developed to replace the existing NAD 83 and NAVD 88.
The changes in these datums will have a significant impact on the users of
geodetic data nation wide. This presentation will describe the existing
components of NSRS and the rational for the need to adopt new reference frames.
|
Download (ppt) (42.83 MB)
|
Quantifying load model errors by comparison to a global GPS time series solution
|
Tonie van Dam
|
Tonie van Dam
|
Tonie M van Dam, Xavier Collilieux, Paul Rebischung, Jim Ray, Zuheir Altamimi
|
2011/12/09
|
San Francisco
|
American Geophysical Union
|
GPS, surface load deformation
|
Show Abstract
Quantifying Load Model Errors by Comparison to a Global GPS Time Series
Solution
Various space geodetic studies over the past two decades have shown that
temporal variations in the distribution of ocean, atmospheric, and
continental water masses cause detectable vertical displacements of the
Earth's surface. Unlike most past research that focused on a single load
component for only vertical motions, we have included the horizontal, as
well as vertical, components and considered atmosphere, non-tidal ocean,
surface water load models. Our geodetic solution is the most current
reprocessed station time series from the International GNSS Service (IGS)
for a global set of 706 stations, each having more than 100 weekly
observations. The long-term stacking of the weekly frame solutions has taken
utmost care to minimize aliasing of local load signals into the frame
parameters to ensure reliable time series of individual station motions.
Our reference load model consists of components from NCEP atmosphere
(corrected for high-resolution topographic variations), ECCO non-tidal
ocean, and LDAS surface water (cubic detrended over 1998 to 2011 to remove
inter-annual artifacts), then combined, linearly detrended, and averaged
to the middle of each GPS week as a posteriori corrections. This reference
model reduces the WRMS scatters of about 72, 63, and 87% of GPS station dN,
dE, and dU components, respectively. Alternative load models, for individual
components or the total, can be tested against the same set of GPS time
series to determine their relative accuracy. For example, not removing a
cubic trend from the LDAS surface water loads causes a global average
quadratic increase in WRMS scatters of about 0.1, 0.1, and 0.5 mm in dN,
dE, and dU. The method is sensitive to load model error differences at the
level of about 0.1 mm in the horizontal components and about 0.2 to 0.3 mm
in the vertical due to residual load aliasing in the GPS time series. We
will report relative accuracy differences for a range of load model pairs.
|
Download (pdf) (4.17 MB)
|
ICON (Ionosphere over CONus): An Overview
|
Dru Smith
|
Dru Smith
|
|
2005/04/12
|
Silver Spring, MD
|
NGS Ionosphere Workshop
|
Ionosphere, ICON, TEC
|
Show Abstract
ICON (Ionosphere over CONus) was an experimental ionosphere model developed at
NGS between 2002 and 2005. It relies solely on ambiguous phase data, and uses a
mathematical truth to arrive at absolute TEC values. This presentation
discusses ICON, and another NGS-sponsored model, called MAGIC (which ultimately
became the SWPC's USTEC engine). Unlike MAGIC, which was a 3-D (plus time)
model, ICON was a 2-D (shell, plus time) model.
ICON never left the experimental stages, due to a variety of instabilities and
the generally better performance of MAGIC. However the mathematical solution to
arrive at UNambiguous TEC from ambiguous phase data remains valid and may prove
useful in the future.
|
Download (ppt) (17.98 MB)
|
Seamless Combination of Bathymetry and Topography: Transforming Vertical Datums
|
Dennis Milbert
|
Dennis Milbert
|
Bruce Parker
|
2001/01/30
|
Silver Spring, MD
|
N/A
|
VDatum, Datums, Topography, Bathymetry
|
Show Abstract
This presentation shows the original work that led to VDatum and the pilot
projects it supported.
|
Download (ppt) (12.05 MB)
|
Kinematic GPS Control of a Hydrographic Survey in Delaware Bay
|
Dennis Milbert
|
Dennis Milbert
|
Jack Riley, Gerry Mader, Miranda Chin, Kurt Hess, Dan Roman
|
2002/08/28
|
Stennis Space Center, Bay Saint Louis, MS
|
GPS Navigation and Datum Workshop
|
Kinematic GPS, Surveying on the Ellipsoid, Vertical Datums
|
|
Download (ppt) (16.69 MB)
|
Real-Time GPS Positioning of Ships To Integrate Navigation Services
|
Dave Zilkoski
|
Dave Zilkoski
|
|
2000/07/06
|
Silver Spring, MD
|
NOS Navigation Services Offices
|
Real Time Positioning, Navigation
|
|
Download (ppt) (4.35 MB)
|
Ionospheric Data Assimilation Methods for Geodetic Applications of the Global Positioning System (GPS)
|
Doug Robertson
|
Doug Robertson
|
Paul Spencer, Gerry Mader
|
2005/04/12
|
Silver Spring, MD
|
Ionosphere Workshop
|
Ionosphere, MAGIC, CORS
|
|
Download (zip) (20.40 MB)
|
Consistency of Crustal Loading Signals Derived from Models and GPS: A Re-examination
|
Xavier Collilieux
|
Xavier Collilieux
|
Paul Rebischung,Tonie van Dam, Jim Ray, Zuheir Altamimi
|
2011/12/07
|
San Francisco
|
American Geophysical Union
|
crustal loads, GPS, GNSS positions
|
Show Abstract
Consistency of Crustal Loading Signals Derived from Models and GPS:
A Re-examination
Various space geodetic studies over the past two decades have detected
vertical displacements of the Earth's surface caused by temporal variations
in the distribution of ocean, atmospheric, and continental water masses.
Most past research has focused on a single component of the mass load and
till now only vertical motions have been examined. Successively stronger
correlations have been seen as improvements have been made in the load
models as well as in measurements by the Gravity Recovery and Climate
Experiment (GRACE) of surface mass changes and by the Global Positioning
System (GPS) of station height variations. Initial comparisons of modeled
surface mass load displacements with GPS heights were most successful for
areas with large signals, such as the Amazon River basin, where the amplitude
of annual height variations reaches ~13 mm. Following large-scale efforts to
reprocess historic GPS data series with modern analysis methods, the most
recent results find that mass load corrections reduce the WRMS scatter of
GPS verticals for ~77% of global networks of more than 100 stations.
We have re-examined this problem but included the horizontal, as well as
vertical, components and used the most current station time series from the
International GNSS Service (IGS) for a global set of 706 stations, each
having more than 100 weekly observations. The long-term stacking of the
weekly frame solutions has taken utmost care to minimize aliasing of local
load signals into the frame parameters to ensure the most reliable time
series of individual station motions. Using a combination of NCEP
atmosphere, ECCO non-tidal ocean, and LDAS surface water load models
(averaged to the middle of each GPS week) as a posteriori corrections, the
WRMS GPS scatters are reduced for 72, 63, and 87% of station dN, dE, and dU
components, respectively. Fitted annual amplitudes are correspondingly
reduced for similar fractions of stations. The weighted mean dU annual
amplitude drops from 3.9 to 1.7 mm with load corrections applied. An absence
of dU improvement is nearly only limited to island and coastal sites with
small load effects, but degradations for dN and dE are more widespread. Some
stations are clearly exceptional due to data problems. The quality and global
coverage of current GPS time series has reached a point that they can be used
as an independent reference to precisely evaluate the relative performance of
competing load models.
|
Download (pdf) (1.62 MB)
|
Better Aircraft Positioning for Airborne Gravimetry: Results from GRAV-D's "Kinematic GPS Challenge" Issued to the GPS Community
|
Theresa Diehl
|
Theresa Diehl
|
Gerald Mader, Sandra Preaux, and Carly Weil
|
2011/12/05
|
San Francisco
|
American Geophysical Union Annual Fall Meeting
|
Kinematic GPS, Airborne Gravity, GRAV-D
|
Show Abstract
To achieve the best airborne gravity data accuracy possible, the GPS position
solutions must provide not just accurate and precise positions, but accurate and
precise velocities and accelerations to be used in calculating gravity
corrections. To our knowledge, no head-to-head comparisons have been done of
available kinematic processing techniques with a focus on producing good
airborne gravity results.
ORIGINAL GOALS:
1. 0.5 mGal or less two-sigma values (precision) for free-air disturbances
calculated with different GPS position solutions, but the same gravity
processing.
2. Close comparisons to EGM08 (accuracy), the best available global gravity
model (Pavlis, et al., 2010), in an area where EGM08 is well-constrained.
Thus, in Fall 2010 the National Geodetic Survey announced the “Kinematic GPS
Challenge� to the
entire GPS community. The Challenge solicited position solutions for two GRAV-D
airborne gravity flights done in Louisiana in Fall 2008. The flights are
described in the data section. The response of the community was outstanding,
with some groups submitting multiple solutions:
Participating groups: 10; Solutions for each flight: 16; Total solutions (for 4
gravity lines): 64. GPS processing types span the range of differential and PPP
solutions, with different methods developed by each group. The results are
presented anonymously here (each solution presented with a unique f##
designator rather than the software’s & developer’s names), protecting the
GPS participants while they discuss these results but allowing the airborne
gravity community to benefit from the early conclusions.
|
Download (pdf) (1.68 MB)
|
Geodesy and GIS
|
Pamela Fromhertz
|
Pamela Fromhertz
|
|
2011/11/10
|
University of Denver, CO
|
GIS Class
|
Accuracy verses Precision; the NSRS; DS-World; CORS; OPUS; Vertical Datums; NGS Ten Year Plan
|
Show Abstract
This presentation provides an overview of why geodesy and datums are important
to GIS. Various tools and products are covered so the user is aware of how they
can use and access the NSRS and its data.
|
Download (zip) (36.85 MB)
|
Dozen New Things for 2-0-Dozen
|
Marti Ikehara
|
Marti Ikehara
|
|
2012/01/12
|
Walnut Creek, CA
|
CLSA East Bay chapter
|
CORS, 2011 Adjustment,Geoid Slope Validation, Beta Programs
|
|
Download (pptx) (7.32 MB)
|
Latest Advancements at the National Geodetic Survey
|
Ronnie Taylor
|
Ronnie Taylor
|
|
2012/01/24
|
Washington, DC
|
91st Annual Meeting of the Transportation Research Board
|
Datum, National Adjustment of 2011, NA2011, GRAV-D, gravity, 2011 Geoid Slope Validation Survey, deflection of the vertical, CORS monograph, Emergency response imagery, remote sensing,
|
|
Download (ppt) (22.05 MB)
|
New Developments for OPUS
|
Gerald L Mader
|
Mark Schenewerk
|
Gerald L Mader
|
2012/01/24
|
Hershey, PA
|
PSLS
|
OPUS
|
|
Download (ppt) (34.01 MB)
|
The NGS Gravity Program Benefits and Opportunities
|
Juliana Blackwell
|
Juliana Blackwell
|
Vicki Childers
|
2012/01/23
|
Phoenix, AZ
|
MAPPS Winter Confernce
|
MAPPS, gravity, GRAV-D
|
Show Abstract
National Geodetic Survey Director, Juliana Blackwell, gave a presentation on
NGS’s Gravity for the Redefinition of the American Vertical Datum (GRAV-D)
program at the Management Association for Private Photogrammetric Surveyors
(MAPPS) winter conference held January 22-23, 2012. MAPPS is an association of
photogrammetry, mapping, and geospatial firms, and this briefing discussed the
importance of GRAV-D and how MAPPS members and NGS can work together and support
one another towards common goals. The new vertical datum in development by NGS
will be important to both the Geographic Information Systems (GIS) and MAPPS
communities, which rely on accurate elevations to perform their missions.
|
Download (ppt) (13.35 MB)
|
CGSIC-CORS User Forum New CORS Coordinates
|
Giovanni Sella
|
Giovanni Sella
|
Jake Griffiths
|
2011/09/19
|
Portland OR
|
CGSIC
|
GPS CORS Coordinates NAD83 IGS08
|
Show Abstract
New Revised CORS Coordinates in IGS08 epoch 2005.00 and NAD 83
(2011/MA11/PA11) epoch 2010.00
|
Download (pptx) (5.42 MB)
|
OPUS improvements and plans
|
Joe Evjen
|
Mark Schenewerk
|
|
2012/02/01
|
Atlantic City, NJ
|
NJSPLS
|
OPUS
|
|
Download (pptx) (24.98 MB)
|
Better Positions and Improved Access to the NSRS
|
Michael L. Dennis
|
Michael L. Dennis
|
|
2012/02/02
|
Atlantic City, NJ
|
New Jersey Society of Professional Land Surveyors
|
NSRS, NA2011, NAD 83(2011), NGS Datasheet
|
Show Abstract
As part of the continuing efforts to improve the National Spatial Reference
System (NSRS), NOAA's National Geodetic Survey (NGS) has performed the National
Adjustment of 2011 (NA2011). This adjustment yielded updated North American
Datum of 1983 (NAD 83) coordinates on passive control stations with positions
determined using Global Navigation Satellite System (GNSS) technology. It is a
simultaneous least-squares adjustment of nearly 80,000 passive control stations
using a nationwide network of over 400,000 GNSS vectors that represent over 4100
survey projects spanning from the mid 1980s to August 2011. NA2011 is
constrained to current NAD 83 coordinates of the NGS Continuously Operating
Reference Station (CORS) network, which is a GNSS-based “active� control
system and the geometric foundation of the NSRS. These NAD 83 CORS coordinates
were determined in the NGS Multi-Year CORS Solution (MYCS) through a combined
solution of all CORS GNSS data from 1994 to April 2011. Constraining NA2011 to
the MYCS optimally aligns the GNSS passive control with the active control,
providing a unified reference frame. The resulting realization gives positions
at an epoch date of January 1, 2010, and it is formally designated as NAD
83(2011) epoch 2010.00.
To ensure consistency in the NSRS, NGS developed a new hybrid geoid model
(GEOID12) for concurrent release with NA2011. GEOID12 is based on a new
gravimetric geoid model (USGG2012) modified using NAD 83(2011) ellipsoid heights
on vertical bench marks. To improve access to the NSRS, NGS developed a new
datasheet format that will provide some of the new information associated with
NA2011, such as detailed accuracy information. The NGS “Bluebook� process
for submitting control surveys for publication has also been improved, including
a new version of the ADJUST least-squares adjustment program.
This workshop describes the methods and results of NA2011, as well as the MYCS
that provides the control for NA2011. The workshop also gives an overview of
GEOID12, the new NGS Datasheet format, and other updates, such as the new
version of ADJUST and new GIS-compatible products and services. NA2011 improves
how NGS meets its wide range of customer needs in providing the basis for
accurate and reliable georeferencing throughout the US and its territories.
Completion of NA2011 – together with related products and services –
represents a significant step toward a more integrated NGS, in terms of both
better positions and improved access to the NSRS.
|
Download (pptx) (130.00 MB)
|
Positioning America for the Future
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2012/02/28
|
Annapolis, MD
|
National States Geographic Information Council (NSGIC) Midyear Meeting
|
NSGIC, GIS, NA2011 GEOID12, geoid, gravity, GRAV-D, NSRS
|
Show Abstract
Juliana Blackwell, Director, NOAA’s National Geodetic Survey (NGS), presented
an overview of why geodesy and datums are important to geographic information
systems at the National States Geographic Information Council (NSGIC) meeting
held February 29 to March 1 in Annapolis, MD. Included in the presentation was a
background of NGS’ modernization efforts for the National Spatial Reference
System (NSRS) that are currently underway, as well as key products and services
of interest to the GIS (geographic information systems) community, including
NGS’s Gravity for the Redefinition of the American Vertical Datum (GRAV-D)
initiative, the National Adjustment of 2011 (NA2011) project, the new GEOID12
gravity model, and new GIS tools and datasets for display and analysis of survey
data. An overview of the socio-economic benefits of NOAA/NGS products and
services will also be provided.
|
Download (ppt) (14.11 MB)
|
NGS Real Time GNSS Positioning User Guidelines
|
William Henning
|
William Henning
|
|
2012/01/24
|
Hershey, PA
|
PSLS 2012 Conference
|
RTN, real time
|
Show Abstract
Surveyors use Real Time GNSS (RT) technology becauseit’s a fast, efficient
(labor saving) positioning tool that can yield survey grade coordinates used in
a wide variety of applications. But, how good do you feel about the data you are
producing with your real time gear? It is all “black box� technology after
all. Are the data collector position quality values displaying precision or are
they displaying accuracy and at what confidence level? What position deltas
would you expect if you get another shot at a different time or with different
weather? What are the factors that might be affecting your data, anyway? Would
it be better to use a new real time network (RTN)to get your data? Is there any
way to have real confidence with a RT established position? As we can see, there
are a lot of questions with this technology
and the answer to all of them is: “It depends�. That’s why NOAA’s
National Geodetic Survey (NGS) has produced a set of single base RT user
guidelines that recently left draft status to become an official NGS document.
This workshop will discuss how you can have real confidence with real time work
and go over the important criteria for the surveyor
to achieve successful field campaigns based on the guidelines. Topics of
discussion for best methods for the field include: constraining local
monumentation, DOP, weather conditions, data collection parameters,multipath,
how RT works, how RT doesn’t work, and many others
emphasizing the attendees’ area of interest.
|
Download (pptx) (15.93 MB)
|
Down to Earth: Datums & Reference Systems, Part II
|
Marti Ikehara
|
Marti Ikehara
|
|
2012/03/02
|
Santa Rosa
|
CLSA Sonoma Chapter
|
IGS08 for CORS, Passive adjustment of 2011, Geoid development, OPUS submissions, DSWorld software
|
Show Abstract
Recent and near-future changes in the geodetic datums and other developments
being done by NGS are presented by the California Geodetic Advisor. She will:
- Discuss how the new geodetic reference frame--IGS08-- was realized,
- Detail the process for the nationwide adjustment of ~80,000 passive
stations,
- Explain the development of the upcoming GEOID12 gravity model
- Introduce the RTN Validation initiative.
Looking to the far future (10 years), you will learn about the developments that
have been initiated to:
- totally revamp the horizontal and vertical datums that define the NSRS,
- obtain airborne gravity measurements to develop a geoid model accurate to 1
cm,
- collect and analyze data for a Gravity Slope Validation Survey.
There will be demonstrations of NGS software and online tools:
- DSWorld for mapping NGS control locations in Google Earth,
- DSWorld for submitting database corrections and updates (recovery notes),
- VDATUM for relating tidal datums to geodetic datums
- HTDP for getting different epoch coordinates
|
Download (pptx) (55.88 MB)
|
Positioning the Pacific: NOAA's Geospatial Activities
|
Juliana Blackwell
|
Juliana Blackwell
|
|
2012/03/06
|
Honolulu, Hawaii
|
Hawaii Pacific Geographic Information Systems (GIS) Conference 2012
|
NGS, Hawaii, Pacific, GIS, geospatial, NGS products and services, geospatial data and services, NOAA Geospatial Platform
|
Show Abstract
NGS Director, Juliana Blackwell, gave the keynote address at The Hawaii Pacific
Geographic Information Systems (GIS) Conference 2012 held in Honolulu, HI March
5 to 9, 2012. Ms. Blackwell's presentation highlighted NGS' and NOAA's
geospatial activities in the Pacific region. Topics covered included an overview
of selected NOAA geospatial data and services supporting mapping and charting,
comprehensive ocean and coastal planning, new approaches for visualizing and
using NOAA data, including the latest mobile applications, and the development
of a new NOAA Geospatial Platform for access to the breadth of NOAA's geospatial
data, services, and applications.
|
Download (ppt) (40.18 MB)
|
Digging For Datums
|
David A. Zenk
|
David A. Zenk
|
|
2012/03/21
|
Breezy Point, MN
|
MNDOT Survey Technical Workshop
|
Datums, Elevations
|
Show Abstract
Understanding the relationships between vertical datums is important, especially
when converting elevations from one datum to another. Unfortunately, the various
datums are not very far apart and it is easy to make mistakes adding or
subtracting datum shifts. The presentation will show the basic relationships
among common datums and advocate an easy to understand method of datum
conversion.
|
Download (pdf) (8.74 MB)
|
The New NAD83(2011) Adjustment in MN
|
David A. Zenk
|
David A. Zenk
|
|
2012/03/21
|
Breezy Point, MN
|
MNDOT Survey Technical Workshop
|
NAD83(2011), Adjustment, Geodetic History in MN
|
Show Abstract
The National Geodetic Survey has readjusted the passive mark network throughout
the United States to reflect the most accurate positions of the CORS network.
The adjustment results and their impacts on Minnesota will be discussed.
|
Download (pdf) (11.34 MB)
|
NGS Activities in Colorado
|
Pam Fromhertz
|
Pam Fromhertz
|
|
2012/02/28
|
Fort Collins, CO
|
Federal Surveyors Workshop
|
CORS, Leveling, heights
|
|
Download (pptx) (2.76 MB)
|
Latest Developments in NGS
|
Pam Fromhertz
|
Pam Fromhertz
|
|
2012/03/03
|
Arvada, CO
|
PLSC Rocky Mountain Surveyors Summit
|
NSRS, CORS, DS-World, RTN, New datums
|
Show Abstract
Technology has changed the face of surveying and mapping, and the National
Geodetic Survey (NGS) is at the forefront in the implementation of many of these
technologies to provide the Nation with a consistent and accurate reference
system. NGS produces the National Spatial Reference System (NSRS) ensuring
projects have the consistency and accuracy desired. There are many tools
available to access the NSRS and these will be highlighted during this session.
In particular, DS-World, CORS and the Online Positioning User Service (OPUS)
will be discussed.
Using Google Earth, DS-World, makes it possible for users to display the
million-plus geodetic survey marks and the GPS Continuously Operating Reference
Stations (CORS) that make up the NSRS. This useful tool can display all the
survey marks available in a particular geographic area and the associated
information about each point, including its description, position, and other
information gathered when the mark was set.
NGS’ OPUS program is highly automated and requires minimal user input
accessing the network of CORS for determining ones position. With OPUS, users
can obtain high-accuracy NSRS coordinates, using only a clear view of the sky
and a survey-grade GPS receiver. OPUS processes GPS data files along with CORS
coordinates to provide results consistent with those of other users. Many
variations have and are evolving.
There are many other developments occurring in NGS that will be presented. These
include: NGS role with the development of real time GPS; Modernization of the
NSRS; the new adjustment (to be completed by 2011); and the GRAV-D program and
how it may change the way we obtain vertical heights.
|
Download (pptx) (26.21 MB)
|
NGS National Height Modernization Overview
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Renee Shields
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Renee Shields
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2012/03/21
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Breezy Point, MN
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2012 Survey Technical Workshop
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Height Modernization, Geoid, Vertical Datums
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Show Abstract
Presentation is a 2-hour talk on the background and components of the NGS
National Height Modernization Program, including how it fits into NGS' Ten-Year
Plan.
|
Download (ppt) (44.72 MB)
|
The Challenges of Change: The Evolution of the NSRS and NGS Geodetic Advisor Program, Part II
|
Marti Ikehara
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Marti Ikehara
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2012/03/25
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Reno, NV
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CLSA/NALS Conference 2012
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Advisors, Learning Resources, CGPS Sources, OPUS, Datasheet, Accuracies, DSWorld
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Show Abstract
Changing Geodetic Advisor Program
LEARNING/CONT EDUCATION: NGS Resources
Non-NGS CGPS Data/Info—PBO and CSRC
OPUS: S, RS, DB, Projects
HTDP
Datasheet Format/Content Changes
VDATUM
DSWORLD Demonstration
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Download (pptx) (10.83 MB)
|
2012 State of NGS
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Marti Ikehara
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Marti Ikehara
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2012/04/05
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Riverside, CA
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LCSO's Geospatial Symposium
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Reference frame improvements, NSRS evolution, FY12 budget, advisor program, coastal products
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Show Abstract
NSRS Ref frame improvements:
For CORS, for passive, Geoid model;
NSRS Evolution:
GRAV-D, GSVS, NSRS revolution;
NGS FY12 Budget & Geodetic Advisor Program;
Coastal Products & Services:
Shoreline Change, VDATUM, SLR, GLOSS, CSC;
Lightning topics
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Download (pptx) (29.49 MB)
|
The Challenges of Change: The Evolution of the NSRS and NGS Geodetic Advisor Program, Part I
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William Stone
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William Stone
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2012/03/25
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Reno, NV
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CLSA/NALS Conference 2012
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CORS, multi-year CORS solution, national adjustment, new datums
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Show Abstract
This presentation discusses the status of the national Continuously Operating
Reference Station (CORS) network and the recent multi-year CORS solution (new
published CORS coordinates), the status of the National Adjustment of 2011
(forthcoming new published coordinates on passive network stations), and the
next generation (in about a decade) of national horizontal and vertical datums.
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Download (pptx) (49.39 MB)
|
National Geodetic Survey Highlights
|
William Stone
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William Stone
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2012/02/10
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St. George, UT
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Utah Council of Land Surveyors 2012 Conference
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CORS, multi-year CORS solution, OPUS, NGS Ten-year Plan, national adjustment, new datums, DSWorld, Geoid Slope Validation Survey 2011
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Show Abstract
This presentation discusses the NGS Continuously Operating Reference Station
(CORS) network, the recent multi-year CORS solution (new CORS coordinates), the
NGS Online Positioning User Service (OPUS), the National Adjustment of 2011
(forthcoming new coordinates for passive control network), the NGS Ten-year Plan
/ plans for new datums (in about a decade), DSWorld software, forthcoming
changes to NGS datasheets, the Geoid Slope Validation Survey of 2011, and other
topics.
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Download (pptx) (62.56 MB)
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NGS Produces New Coordinates: Is it stil NAD83? Past, Present, Future
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Marti Ikehara
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Marti Ikehara
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2012/04/12
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Sacramento, CA
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CalGIS Conference 2012
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NAD83 Realizations, Passive adjustment, Datasheet changes, Advisors
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Show Abstract
On September 6, 2011, the National Geodetic Survey (NGS) published new
coordinates for the nationwide continuous GPS network called CORS, which had not
been updated in 9.5 years. The official datum of the National Spatial Reference
System is still NAD83 but the realization of the datum changes with each
adjustment that generates new coordinates. This talk will explain what the
metadata should include, particularly in California, and give a few examples of
the differences among coordinates, between 1986 and present, even if all are
referenced to “NAD83.� NGS anticipates that, in 10 years, the NAD83 datum
will be replaced by a truly geocentric datum that will be related to the
International Terrestrial Reference Frame datum. Although the horizontal
position (latitudes and longitudes) will of course change, it is notable that
the ellipsoid heights could differ by 0.5 meters.
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Download (pptx) (15.67 MB)
|
Dozen New Things in 2012, April version
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Marti Ikehara
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Marti Ikehara
|
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2012/04/26
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Marysville and Yuba City
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CT D03 and CLSA No Counties chapter
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CORS, multi-year CORS solution, national adjustment, new datums, new DS format
|
|
Download (pptx) (7.67 MB)
|
National Geodetic Survey Highlights
|
Dave Minkel - Michael Dennis
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Dave Minkel
|
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2012/04/28
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Tempe, AZ
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APLS Annual Conference
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CORS, OPUS, NA2011, new datums
|
|
Download (pptx) (55.01 MB)
|
Evaluations of Global Geophysical Fluid Models Based on Broad-band Geodetic Excitations
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Jim Ray
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Wei Chen
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Jim Ray
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2012/04/20
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Vienna, Austria
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Workshop of the IERS Global Geophysical Fluids Center
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Earth orientation, polar motion excitation, global fluids
|
|
Download (ppt) (4.32 MB)
|
High-Accuracy Subdaily ERPs from the IGS
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Jim Ray
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Jim Ray
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Jake Griffiths
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2012/04/23
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Vienna, Austria
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European Geosciences Union General Assembly 2012
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Earth orientation, polar motion, length of day, IGS
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Show Abstract
Conclusions
• IGS produces Ultra-rapid ERPs with subdaily resolution & high accuracy
– observed ERPs updated every 6 hr with 15 hr latency
– PM accuracy roughly similar to IGS Finals: 25 to 30 μas
– IGS Rapid PM accuracy may be even better: 15 to 16 μas
– IGU dLOD accuracy may be better than IGS Finals: ~5 μs
– further study needed to assess accuracy of IGS ERPs
• Main (systematic) error components are probably:
– errors in IERS subdaily EOP tide model
– orbit mis-modeling (draconitic signals)
– instabilities in terrestrial reference frame (though none detected
directly)
• IGS Ultra-rapid PM predictions better than operational services
– IGU dLOD predictions similar to operational service
• IGS Ultra-rapid ERP observations & predictions should be assimilated by
operational EOP prediction services !
|
Download (pdf) (0.48 MB)
|
IGS preparations for the next reprocessing and ITRF
|
Jake Griffiths
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Jake Griffiths
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Paul Rebischung, Bruno Garayt, Jim Ray
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2012/04/26
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Vienna, Austria
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EGU 2012 General Assembly
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IGS, ITRF, orbit, EOP, TRF, GPS
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Show Abstract
The International GNSS Service (IGS) is preparing for a second reanalysis of the
full history of data collected by the global network using the latest models and
methodologies. This effort is designed to obtain improved, consistent satellite
orbits, station and satellite clocks, Earth orientation parameters (EOPs) and
terrestrial frame products using the current IGS framework, IGS08/igs08.atx. It
follows a successful first reprocessing campaign, which provided the IGS input
to ITRF2008. Likewise, this second campaign (repro2) should provide the IGS
contribution to the next ITRF. We will discuss the analysis standards adopted
for repro2, including treatment of and mitigation against non-tidal loading
effects, and improvements expected with respect to the first reprocessing
campaign.
International Earth Rotation and Reference Systems Service (IERS) Conventions of
2010 are expected to be implemented. Though, no improvements in the diurnal and
semidiurnal EOP tide models will be made, so associated errors will remain.
Adoption of new orbital force models and consistent handling of satellite
attitude changes are expected to improve IGS clock and orbit products. A priori
Earth-reflected radiation pressure models should nearly eliminate the ~2.5 cm
orbit radial bias previously observed using laser ranging methods. Also, a
priori modeling of radiation forces exerted in signal transmission should
improve the orbit products. And use of consistent satellite attitude models
should help with satellite clock estimation during Earth and Moon eclipses.
Improvements of the terrestrial frame products are expected from, for example,
the inclusion of second order ionospheric corrections and also the a priori
modeling of Earth-reflected radiation pressure. Because of remaining unmodeled
orbital forces, systematic errors will however likely continue to affect the
origin of the repro2 frames and prevent a contribution of GNSS to the origin of
the next ITRF. On the other hand, the planned inclusion of satellite phase
center offsets in the long-term stacking of the repro2 frames could help in
defining the scale rate of the next ITRF.
|
Download (pdf) (0.95 MB)
|
Gravity and the World Height System
|
Daniel R. Roman
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Daniel R. Roman
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2012/05/05
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Rome, Italy
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Reference Frames in Practice Seminar (F.I.G.)
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gravity, geoid, heights, vertical reference
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Show Abstract
The gravity field is directly related to the structure of the Earth and how its
mass is distributed. Every piece of mass creates a potential of gravity
(geopotential) that drops off with distance. The cumulative effect of all these
produces the Earth's gravity field. This session will focus on the relationship
between various aspects of the Earth's gravity field such as the geoid,
geopotentials, gravity, deflections of the vertical, and physical heights (e.g.,
above mean sea level). It covers different means of observing the gravity field
and how they are combined to produce models for height determination both at
global scales, such as the World Height System, and locally for National
Vertical Datums.
|
Download (ppt) (12.75 MB)
|
Beyond GEOID12: Implementing a New Vertical Datum for North America
|
Daniel R. Roman
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Daniel R. Roman
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neil D. Weston
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2012/05/08
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Rome, Italy
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F.I.G. Session TSC04B: Heights, Geoid, & Gravity
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Positioning, Heights, GPS/Leveling, Geoid, Vertical Datum
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Show Abstract
The National Geodetic Survey (NGS) is responsible for maintaining both the
horizontal and vertical datums within the U.S. National Spatial Reference System
(NSRS), which are the North American Datum of 1983 (NAD 83) and the North
American Vertical Datum of 1988 (NAVD 88), respectively. NGS periodically
produces hybrid geoid height models that transform between these datums to
facilitate GPS/leveling in surveying as well as other engineering and scientific
activities. The GEOID12 model represents the latest effort in this series.
However, both NAD 83 and NAVD 88 have significant systematic problems, which the
current hybrid geoid height models faithfully replicate. While the datums remain
internally consistent (i.e., precise) they are inconsistent with other reference
systems at the meter level (i.e., not accurate). Comparisons at tide gauges and
with global satellite gravity field models demonstrated a meter level
cross-continent trend in NAVD 88 likely due to accumulated leveling errors in
the adjustment that created it. Likewise NAD 83 is known to have a 2.2 meter
offset from IGS 2008. The Gravity for the Redefinition of the American Vertical
Datum (GRAV-D) project was started to realize a new vertical datum that is both
accurate and precise. The aim of the project is to produce a gravimetric geoid
height model that is accurate to cm-level and can be combined with an improved
geometric reference frame to produce similarly improved physical heights,
removing entirely the need to have “hybrid� geoid models which absorb
systematic datum errors. Several factors are critical to ensuring this works. In
anticipation of its adoption in 2022 at the completion of GRAV-D, an optimum
geopotential surface (geoid) was recently selected based on comparisons with
tidal bench marks around Canada and the United States and some portions of the
Caribbean. A geopotential value of 62,636,856.00 m2/s2 best fit available data.
This value is the same as that adopted by the International Astronomical Union
(IAU) & the International Earth Rotation and Reference Systems Service (IERS)
and is one of many that have been offered as the best representative of global
mean sea level (MSL). Comparisons all around the North American continent with
tide gauges, satellite altimeter measurements of the ocean surface, and models
of ocean height variability all support adoption of this number as the best
estimate of MSL for North America and future vertical reference systems defined
for the United States and Canada. Canada will be adopting this value and a geoid
height model based on it as their official vertical datum in 2013 while the
United States will follow suit in 2022. The United States continues to collect
aerogravity to remove systematic errors in the terrestrial gravity data holdings
to ensure that a cm-level of accuracy is achieved. This is on track and should
be accomplished as planned in 2022 with a new vertical datum realized by a
gravimetric geoid height model and GNSS observations.
|
Download (ppt) (4.40 MB)
|
Height Modernization in the U.S.: Implementing a Vertical Datum Referenced to a Gravimetric Geoid Model
|
Renee L. Shields
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Renee L. Shields
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Christine Gallagher
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2012/05/08
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Rome, Italy
|
F.I.G. 2012 Working Week
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Height Modernization, Geoid, Vertical Datums
|
Show Abstract
In the United States, since the mid-late 1990’s, the Height Modernization
Program has worked with the user community through education, and providing
models, tools, and guidelines to enable access to the country’s official
vertical reference frame, the North American Vertical Datum of 1988 (NAVD 88),
using the Global Navigation Satellite System (GNSS). The program has focused on
using data from stations with accurate leveled orthometric heights and high
accuracy GNSS ellipsoid heights together with a gravimetric geoid model to
create a geoid model that is fit specifically to NAVD 88.
The accuracy of the geoid model and the capability of GNSS to measure heights
have greatly improved. Users expect faster, more accurate results. But even
with Height Modernization, maintaining the NAVD 88 through passive control and
leveling is resource intensive. In dynamic regions in particular, the surveying
community using these new technologies can now see how the changes in positions
over time impact their work. Movement and velocity models have to be built into
the process, and the very definition of the national datum must be something we
can maintain. Like many other countries, the National Geodetic Survey (NGS) has
come to the conclusion that this is only possible using an accurate gravity
model and GNSS. In ten years, NGS will be replacing the NAVD 88 with a GNSS
based vertical reference frame. But now that that decision has been made, how do
they implement a new reference frame on a country-wide or continent-wide scale
that is so vastly different that the reference frame people have used for over
a 140 years?
While addressing the needs of the user community to access the NAVD 88 during
the next decade, the Height Modernization Program must also prepare that same
community for the transition to a new kind of reference frame. The Height
Modernization Program plan will include components of education, models, tools,
and guidelines that will bridge the old and new ways of accessing the vertical
datum. NGS will work closely with other federal, state, and local mapping
agencies and organizations to make sure the infrastructure and processes are in
place to support access to a National Spatial Reference System that is global
and dynamic.
|
Download (ppt) (3.19 MB)
|
Forthcoming Changes to the National Spatial Reference System
|
William Stone
|
William Stone
|
|
2012/05/16
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Las Vegas, NV
|
Nevada Geographic Information Society
|
CORS, Mutli-year CORS Solution, National Adjustment of 2011, new datums
|
Show Abstract
The National Oceanic and Atmospheric Administration’s National Geodetic Survey
(NGS) is planning substantial changes to the National Spatial Reference System
(NSRS) – the national system of latitude, longitude, elevation, and related
geodetic models and tools – which, when implemented in a decade or so, will
positively impact surveying and mapping activities nationwide. The new NSRS will
provide improved accuracy and efficiency in the nation’s positioning
infrastructure through enhanced utilization of the Global Navigation Satellite
System (GNSS) and other modern technologies. Planned changes to the NSRS
include the definition of a new vertical datum to replace the North American
Vertical Datum of 1988 (NAVD88) and the definition of a new geometric datum to
replace the North American Datum of 1983 (NAD83). This presentation will review
the current status of national datums and will present a description of the new
datums, the need for their implementation, some of the outstanding issues yet to
be resolved, and considerations for a smooth transition.
|
Download (ppt) (43.51 MB)
|
Status of the current multi-year CORS solution
|
Jake Griffiths
|
Jake Griffiths
|
M. Cline, R.L. Dulaney, S. Hilla, W.G. Kass, J. Ray,J.R. Rohde, G. Sella, T. Soler and R. Snay
|
2010/05/22
|
Silver Spring, MD
|
2010 NGS Convocations
|
reprocessing, CORS, GPS, orbits, frames
|
|
Download (pdf) (5.06 MB)
|
Reanalysis of GPS data for a large and dense regional network tied to a global frame
|
Jake Griffiths
|
Jake Griffiths
|
J.R. Rohde, M. Cline, R.L. Dulaney, S. Hilla, W.G. Kass,J. Ray, G. Sella, R. Snay, T. Soler and Z. Altamimi
|
2010/10/05
|
Marne-la-Vallee, France
|
Reference Frames for Applications in Geosciences (REFAG2010)
|
dense networks, processing, global frames, GPS
|
Show Abstract
The National Geodetic Survey (NGS) has recently reprocessed the full history of
Global Positioning System (GPS) data collected from 1994.0 to 2010.5 at stations
of the International GNSS Service (IGS) global tracking network and at stations
of the U.S. Continuously Operating Reference Stations (CORS) network managed by
NGS. This reprocessing effort focuses on using the latest models and
methodologies to accurately determine regularized positions and secular
velocities for CORS relative to the International Terrestrial Reference Frame of
2008 (ITRF2008).
The reanalysis consists of reducing the time series of RINEX observations to
obtain a fully consistent set of GPS satellite orbits, Earth Orientation
Parameters (EOPs) and weekly station positions using the NGS PAGES software. In
order to achieve the best available tie to the global framework, reduction of
RINEX observations is accomplished in two stages. The first stage is
specifically designed to obtain orbits, EOPs and station positions for sites in
the global network, consisting mostly of IGS stations. The products resulting
from this first stage of the reanalysis were submitted to the recent IGS
reprocessing campaign. The second stage is designed to obtain a time-series of
weekly SINEX files containing in addition station positions for sites in the
much denser CORS network. The CORS+global SINEX files are then stacked and
aligned to ITRF2008 using the CATREF software from Institut Géographique
National (IGN). The entire process results in positions and velocities for all
CORS in a fully-consistent global framework that can be aligned to the ITRF
accurately and consistently.
Challenges in this work include: accounting for all position and velocity
discontinuities, and tying a large and dense regional network to a global
framework without causing significant distortions to the frame. Here, we present
a summary of the automated strategies used for finding undocumented
discontinuities, an assessment of distortions caused by tying the CORS network
to the global frame and a discussion of the updated CORS velocity field.
|
Download (pdf) (4.62 MB)
|
Ensuring Accurate, Consistent Measurements with GPS
|
Pamela Fromhertz
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Pamela Fromhertz
|
|
2012/06/20
|
Denver, CO
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USGS Core Science Systems
|
2011 readjustment, new datums, DS-World, OPUS, NSRS, advisor program, USGS, GPS, datum differences, GRAV-D
|
Show Abstract
Demands for accuracy are increasing and the use of geospatial technologies, such
as Geographical Information Systems (GIS) continue to rise. But how often do you
have problems with data not aligning in your GIS? Knowing how your data is
collected in terms of reference systems, coordinate systems, and datums, is
growing more important to ensure your data layers do align properly.
The National Oceanic Atmospheric Administration’s National Geodetic Survey
(NGS) provides the basis for the critical geospatial infrastructure called the
National Spatial Reference System (NSRS). The NSRS consists of the North
American Datum of 1983 (NAD83) and the North American Datum of 1988 (NAVD88).
Come hear about the differences in datums and why this is important in your work
and the USGS products. There are several programs (DS-World, OPUS) that will be
discussed along with planned replacements to both NAD83 and NAVD88.
|
Download (ppt) (30.18 MB) Download (pdf) (15.72 MB)
|
CDOT Regional Operational Site Visits
|
Pamela Fromhertz
|
Pamela Fromhertz
|
|
2012/05/31
|
CDOT Regional Offices
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CDOT Regions (See details below)
|
NSRS, Multiyear CORS Solution, Readjustment, Geoid 12, GRAV-D, heights, New data sheets, CDOT CORS/OPUS Team efforts, DS-World, OPUS, CBLs, Advisor Program, New Datums
|
Show Abstract
Regional Operational Site visits are held with CDOTs six regions annually to provide an update of the latest developments occurring in NGS and discuss specific projects the regions are working on. This year, in addition, training was provided on using OPUS-DB. Meetings were held on the following dates and locations:
R1 - May 18, 2012 - Denver, CO
R2 - May 3, 2012 - Pueblo, CO
R3 - January 31, 2012 - Grand Junction, CO
R4 - May 31, 2012 - Greeley, CO
R5 - Scheduled for September 2012
R6 - May 1, 2012 - Denver, CO
|
Download (zip/ppt) (175 MB)
Download (zip/pdf) (139 MB)
|
GNSS and Elevation Certificates in North Carolina
|
Gary Thompson, NC Geodetic Survey
|
Gary Thompson
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Scott Lokken
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2012/07/12
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virtual - webinar
|
Height Mod monthly teleconference
|
GNSS, Elevation Certificates
|
|
Download (pdf) (0.97 MB)
|
Antenna Calibration at the National Geodetic Survey
|
Andria Bilich
|
Andria Bilich
|
Gerald L Mader
|
2012/07/25
|
Olsztyn, Poland
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IGS Workshop
|
GPS, antenna calibration, absolute calibration
|
Show Abstract
NOAA’s National Geodetic Survey (NGS) conducts antenna calibrations of
receiving antennas in order to provide more accurate access to the National
Spatial Reference System (NSRS), as an essential service for the surveying,
mapping, and engineering infrastructure of the U.S. Antenna calibrations are an
essential component of GNSS data processing and are used by both vendor- and
university-supplied software as well as NGS’ Online Positioning User Service
(OPUS). It should be noted that NGS constituents use a much larger variety of
antennas than are present in the IGS network. Therefore NGS is interested in
providing calibrations for a wide variety of geodetic-grade antennas, from types
in use at IGS reference stations to rover antennas not normally seen in the IGS
network.
Since 1994, NGS has computed relative antenna calibrations for more than 350
antennas. In recent years, the geodetic community has moved to absolute
calibrations - the IGS adopted absolute antenna phase center calibrations in
2006, and NGS's CORS group began using absolute antenna calibration upon the
release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD
83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and
have been converted to absolute, it is considered best practice to independently
measure phase center characteristics in an absolute sense.
Consequently, NGS has developed and operates an absolute calibration system.
These absolute antenna calibrations accommodate the demand for greater accuracy
and for 2-dimensional (elevation and azimuth) parameterization. NGS will
continue to provide calibration values via the NGS web site
www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as
well as the legacy ANTINFO format.
The NGS absolute system is located in Corbin, Virginia, and uses field
measurements and actual GNSS satellite signals to quantitatively determine the
carrier phase advance/delay introduced by the antenna element. In this poster,
we intend to cover several topics of interest to the IGS community, by:
* describing the NGS calibration facility and assumptions which underpin the
setup and method
* discussing the observation models and strategy currently used to generate NGS
absolute calibrations
* demonstrating that NGS absolute PCO and PCV values are consistent with other
IGS-sanctioned absolute antenna calibration facilities
* outlining future planned refinements to the system
* discussing features of the NGS Calibration Policy and Procedures documents,
which outline the relationship between NGS and its customers
|
Download (pdf) (0.84 MB)
|
GEOID12 Model Overview
|
Daniel Roman
|
Daniel Roman
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Xiaopeng Li and Simon Holmes
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2012/07/22
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San Diego Convention Center
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ESRI Survey Summit (AAGS and NSPS members)
|
GEOID12, USGG2012, GPSBM2012, OPUSDBBM12
|
Show Abstract
The recently released GEOID12 model provides an update for surveying and
engineering applications requiring transformations between the North American
Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88).
GEOID12 incorporates a number of recently completed adjustments to the NGS
Database. The National Adjustment of 2011 (NA2011) was completed and released at
the same time as GEOID12 and represents the most recent realization of
ellipsoidal or geometric coordinates for bench marks. This complements recent
adjustments to the leveled heights in several states particularly those in the
central Gulf Coast region where subsidence is an issue. Underpinning this is the
United States Gravimetric Geoid for 2012 (USGG2012) that incorporates gravity
field observations from multiple satellite gravity missions (GRACE, GOCE).
USGG2012 provides the fine detail that fills in the information in between the
control data represented by both the GPS on leveled Bench Marks for 2012
(GPSBM2012) and archived values in the OPUS-DB on leveled Bench Marks for 2012
(OPUSDDBM12). The preponderance of these control points derive from GPSBM2012
(around 23,000) but the OPUSDBBM12 provides additional coverage to reduce
interpolation across gaps in the GPSBM2012 coverage. The control data were used
to develop a conversion surface with Least Squares Collocation following the
same techniques used for GEOID03 and GEOID09. This surface provides the
transformation necessary to change USGG2012 into GEOID12. It also provides
insight into the expected shift between NAVD 88 and the future vertical datum of
the United States to be implemented in 2022.
|
Download (pptx) (7.85 MB)
|
Rotational Errors in IGS Orbit & ERP Products
|
J. Ray
|
J. Ray
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J. Griffiths, P. Rebischung, J. Kouba, W. Chen
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2012/07/26
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Olsztyn, Poland
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IGS Workshop 2012
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GPS orbits, Earth rotation parameters, IGS
|
Show Abstract
* Systematic rotations are a leading IGS error
- they affect all core products except probably clocks
* Sources include defects in:
- IERS model for 12h + 24h tidal ERP variations
- intra-AC product self-consistency & use of over-constraints
- AC realizations of ITRF
- models for GNSS orbit dynamics (SRP, gravity field variations)
* Examine evidence in IGS products
* Finals appear rotationally less stable than Rapids !
|
Download (ppt) (3.15 MB)
|
IGS Classic Products, Status and Towards the Future
|
Jake Griffiths
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Jake Griffiths
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Kevin Choi
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2012/07/23
|
Olsztyn, Poland
|
IGS 2012 Workshop
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IGS products
|
Show Abstract
The International GNSS Service (IGS) continues to provide satellite orbits and
clocks, station clocks, Earth orientation parameters (EOPs), and terrestrial
reference frame products. Currently, there are three product lines, namely the
IGS Final, the IGS Rapid, and the IGS Ultra-rapid. These products are made
available on a weekly basis, with a delay up to 13 (for the last day of the
week) to 20 (for the first day of the week) days. These products are the basis
for the IGS terrestrial reference frame and are intended for those applications
demanding the highest internal consistency and best quality. The IGS Rapid
products have a quality comparable to that of the Final products. They are made
available on a daily basis with a delay of about 17 hours after the end of the
previous observation day. IGS Ultra-rapid products are released four times per
day with 3 hours latency—i.e., released at 03:00, 09:00, 15:00, and 21:00
UTC—making them available for real-time and near real-time use. Contrary to
all other IGS orbit products, the IGS Ultra-rapid orbit files contain 48 hours
of tabular orbital ephemerides, and the start/stop epochs continuously shift by
6 hours with each update. The first 24 hours of each IGS Ultra-rapid orbit are
based on the most recent GPS observational data. The next 24 hours of each file
are predicted orbits, extrapolated from the observed orbits. Normally, the
predicted orbits between 3 and 9 hours into the second half of each Ultra-rapid
orbit file are most relevant for true real time applications. All other orbit
products contain only the 24 hours from 00:00 to 23:45 UTC.
The IGS generally aims to provide ~1 cm orbits and ~1 mm terrestrial frame
products to meet the most demanding user needs. While the goal has not yet been
met, the IGS has made good progress. Ray and Griffiths recently reported that
the IGS GPS Final orbits have an accuracy better than 2.5 cm; the Rapids are of
similar quality, with an inaccuracy of ~2.5 cm; and the 24h observed parts of
the IGS Ultra-rapids have an accuracy of ~3.0 cm while the 24h predicted parts
have an accuracy of about 5 cm. Inaccuracies of the IGS GLONASS orbits are about
twice as large as for GPS. About half of the total error in the GPS orbits can
be attributed to systematic time-varying rotational misalignment of the orbital
frames (Griffiths and Ray, 2009; Gendt et al., 2010; Griffiths et al., 2012).
Orbit mismodeling also contributes to these errors. Sub-daily alias and
draconitic errors in the GPS orbits are largely caused by errors in the IERS
diurnal and semi-diurnal EOP model (Griffiths et al., 2011). For most
applications, the user of IGS orbit products will not notice significant
differences between results obtained using the IGS Final and the IGS Rapid
products. IGS weekly realizations of the combined terrestrial frame have
accuracies of ~2 mm in each orthogonal horizontal component and ~5 mm in the
vertical. The errors in the terrestrial frame probably arise mainly from
inadequacies of the GNSS tracking stations, including the presence of
uncalibrated radomes, near-field multipath effects and equipment changes, and
mismodeling of tropospheric and ionospheric propagation delays. Many of these
outstanding issues are indeed the focus of the IGS second reprocessing (i.e.,
IG2) campaign, the processing for which could be underway by early 2013. If all
model changes intended for IG2 are in fact made, then the orbit and terrestrial
frame errors should be reduced. However, there is currently no plan for a new
IERS sub-daily EOP model or for mitigating inadequacies of the tracking
stations, so one should temper their expectations for these aspects.
|
Download (pdf) (2.52 MB)
|
Do Annual Geopotential Variations Affect IGS Products?
|
J. Ray
|
J. Ray
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S. bettadpur, J. Ries, T.-S. Bae, X. Collilieux, T. van Dam, K. Choi, J. Griffiths
|
2012/07/26
|
Olsztyn, Poland
|
IGS Workshop 2012
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geopotential variations, GPS orbits
|
Show Abstract
* Test effect of GRACE RL05 annual model fits from CSR
- consider terms (2,0), (2,1), (2,2), & (3,1)
* Compare GPS results for two extreme weeks
- 1668 = 25 - 31 Dec 2011
- 1694 = 24 -30 Jun 2012
* Impacts at levels up to several mm
* Other ACs should test & consider using in Repro2
|
Download (ppt) (2.08 MB)
|
Datums and Tools to Connect Geospatial Data Accurately
|
Pamela Fromhertz
|
Pamela Fromhertz
|
|
2012/08/21
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across country webinar
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USGS Natural Science Information Team
|
NSRS, datums, CORS, OPUS, DS-World
|
Show Abstract
Requested presentation to primary group within USGS who interfaces with public.
The presentation covered the basics of NGS, the NSRS, datums, NGS tools and
products such as DC-World, CORS, OPUS as well as NGS-USGS collaborative
projects.
|
Download (ppt) (28.09 MB)
|
National Geodetic Survey–Continuously Operating Reference Stations & Online Positioning User Service
|
William Stone
|
William Stone
|
|
2012/07/24
|
San Diego, CA
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Esri User Conference
|
CORS, OPUS, geodesy, datums
|
Show Abstract
This presentation describes the NOAA/National Geodetic Survey’s network of
permanent GNSS Continuously Operating Reference Stations (CORS) and the related
Online Positioning User Service (OPUS) utility. The CORS network and OPUS both
support centimeter-level positioning capability, thereby enhancing a broad range
of user applications, including those demanding extremely high positional
accuracy. The material presented should be of interest to professionals involved
in surveying, mapping, GIS, and other geospatial disciplines.
The CORS network comprises a network of approximately 2,000 sites, each
containing a geodetic-quality GNSS receiver
whose data are freely available via the Internet. Presentation topics include
the development of the CORS network, CORS
applications, and CORS data access.
OPUS is an automated utility that processes submitted GNSS observation data with
respect to the CORS network and provides positional results to the submitter via
email, usually within minutes. The development, use, and applications of OPUS
will be discussed.
|
Download (ppt) (11.23 MB)
|
Absolute Gravimetry in NGS: Instrumentation and Applications
|
Daniel Winester
|
Daniel Winester
|
|
2012/09/17
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Lafayette, CO
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Micro-g LaCoste workshop
|
gravity, GRAV-D
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Show Abstract
Summary of NGS absolute gravity and related activities over time, emphasizing
station coverage, GRAV-D, GSVS-11 and SAVSARP.
|
Download (pptx) (21.77 MB)
|
Datums and Tools to Connect Geospatial Data Accurately
|
Pamela Fromhertz
|
Pamela Fromhertz
|
|
2012/09/18
|
Denver, CO
|
ESRI Southwest User Conference
|
Datums, Accuracy, NSRS, Tools, DS-World, CORS, OPUS, metadata, geoid, GRAV-D
|
Show Abstract
Demands for accuracy are increasing and the use of geospatial technologies, such
as Geographical Information Systems (GIS) continue to rise. But how often do you
have problems with data not aligning in your GIS? Knowing how your data is
collected in terms of reference systems, coordinate systems, and datums, is
growing more important to ensure your data layers do align properly.
The National Oceanic Atmospheric Administration’s National Geodetic Survey
(NGS) provides the basis for the critical geospatial infrastructure called the
National Spatial Reference System (NSRS) to ensure projects have the consistency
and accuracy desired. The NSRS consists of the North American Datum of 1983
(NAD83) and the North American Datum of 1988 (NAVD88).
Come hear about the differences in datums and why this is important in your
work. There are several programs (DS-World, OPUS) that will be discussed along
with planned replacements to both NAD 83 and NAVD 88.
|
Download (pdf) (14.04 MB)
|
Datums and Tools to Connect Geospatial Data Accurately
|
Pamela Fromhertz
|
Pamela Fromhertz
|
|
2012/09/20
|
Denver, CO
|
GIS in the Rockies
|
Datums, Accuracy, NSRS, Tools, DS-World, CORS, OPUS, metadata, geoid, GRAV-D
|
Show Abstract
Demands for accuracy are increasing and the use of geospatial technologies, such
as GIS continue to rise. But how often do you have problems with data not
aligning in your GIS? Knowing how your data is collected in terms of reference
systems, coordinate systems, and datums, is growing more important to ensure
your data layers do align properly.
The National Geodetic Survey produces the National Spatial Reference System
(NSRS) ensuring projects have the consistency and accuracy desired. The NSRS
consists of the North American Datum of 1983 (NAD83) and the North American
Datum of 1988 (NAVD88). There are many tools available to access the NSRS
(DS-World, CORS, OPUS) and these will be highlighted during this session.
DS-World, makes it possible for users to display the million-plus geodetic
survey marks and the GPS Continuously Operating Reference Stations (CORS) that
make up the NSRS in GoogleEarth. This tool displays survey marks and its
associated information. You can access, locate and survey these marks and tie
your data layers directly to the NSRS and the most recent datums.
NGS’ OPUS program is highly automated and requires minimal user input
accessing the network of CORS for determining ones position. OPUS processes GPS
data files along with CORS coordinates to provide results consistent with those
of other users in the NSRS.
There are many developments occurring in NGS that will be presented including
the new adjustment, new datums (in 2022) and the GRAV-D program (which will
change the way we obtain vertical heights).
|
Download (pdf) (24.56 MB)
|
Transitioning to the new reference frame NAD 83(2011)2010.00
|
Mark L. Armstrong, PLS
|
Mark L. Armstrong
|
|
2012/09/21
|
Salem, OR
|
OSBEELS Symposium
|
Transitioning to the new reference frame NAD 83(2011)2010.00 from NAD 83(CORS96)2002.00
|
Show Abstract
Transitioning to the new reference frame NAD 83(2011)2010.00 from NAD
83(CORS96)2002.00 in the Pacific Northwest.
Topics include:
-National Spatial Reference System
New NAD 83 reference frame: NAD 83(2011, MA11, PA11)epoch 2010.00
-Global Reference Frame Coordinates: IGS08(2005)
-Review the change to absolute antenna calibrations
-NA2011 completed (~80k passive marks)
-GEOID12A (now available)
-Review how CORS positions are computed with the MYCS
-The OPUS Suite
-OPUS Projects (beta)
-Updating coordinates for the ORGN (Real-Time Network) from
NAD 83(COR96)epoch 2002.00 to NAD 83(2011)epoch 2010.00
|
Download (pdf) (7.42 MB)
|
Integration of Gravity Data Into a Seamless Transnational Height Model for North America
|
Daniel Roman
|
Daniel Roman
|
Marc Véronneau, David Avalos, Xiaopeng Li, Simon Holmes, and Jianliang Huang
|
2012/10/10
|
San Servolo, Venice, Italy
|
Gravity, Geoid, and Height Systems (GGHS)
|
gravity, geoid, vertical datum
|
Show Abstract
The National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic
Survey (NGS) is responsible for defining, maintaining, and providing access to
the National Spatial Reference System (NSRS) for states and territories of the
United States. To best ensure the integrity of the NSRS, additional information
outside of the U.S. is required. To that end, NGS has been engaged with Mexico
for the past half-decade and Canada for the past two decades. The two ongoing
satellite gravity missions, GRACE and GOCE, provide a broader reference system
in which to define a unified vertical reference system for height determination.
The IAG Sub-Commission 2.4c for Gravity and Geoid in North and Central America
is specifically focused upon defining a geoid height model for that purpose.
Together the United States, Canada, and Mexico have been working toward
determining and fixing any systematic defects in national gravity datasets and
making these mutually available. Most of the data in Canada have been deemed
sufficient already by way of comparisons to global satellite gravity field
models. Significant problems remain in American and Mexican data sets that need
to be resolved. The Gravity for the Redefinition for the American vertical Datum
(GRAV-D) project is the primary means for addressing this in the U.S., while
Mexico has adopted a program that will revisit all base station ties to
determine any systematic effects on derived relative gravity values. For the
U.S., grids of aerogravity data have been integrated with the satellite models
to provide a reference field for determining and fixing the systematic errors in
over 1400 different surveys containing biases of to 6 mGal across regions of
several hundreds of kilometers. The impact of removing these systematic effects
was to remove many decimeters of error from the derived geoid height model and
thereby move closer to the goal of a cm-level accurate model. Overflights into
Canada and Mexico will likewise ensure integrity of the model across the U.S.
border into the broader transnational region. Mexico has been engaged with
countries in Central America and the Caribbean to conduct training on gravity
collection and development of geoid height models, with several countries moving
forward now with collection programs and data sharing. Data sharing with IAG
Sub-commission 2.4.b, Gravity and Geoid in South America, has also been
discussed with the intent to obtain data to the Equator and provide as much data
as the IAG SC 2.4b group needs to complete their model. This will provide a
seamless transition over the Americas consistent with the intent of a unified
world height system.
|
Download (ppt) (5.38 MB)
|
Progress towards a common North American Geoid in 2012
|
Daniel Roman
|
Daniel Roman
|
Yan Wang & Xiaopeng Li
|
2012/06/04
|
Banff, Canada
|
Canadian Geophysical Union/Geoid Workshop
|
Geoid, Datum, W0 adoption, North America
|
Show Abstract
The release of USGG2012 marks another step closer to a common North American
Geoid and future Vertical Height System. The geopotential surface adopted in
USGG2012 was determined after careful analysis of geopotential values at tide
gauges around Canada and the United States spanning the Pacific, Gulf of Mexico,
and Atlantic regions as well as parts of the Arctic. The intent was to determine
a value that best fits tide MSL around the continent. Models of ocean topography
were also used to mitigate local variations. Additionally, comparisons were made
to multiple regional and global models to settle upon the optimal value, which
will also be utilized in CGG2013. CGG2013 will mark the first use of a geoid
height model to define a vertical datum in Canada. The United States is
committed to moving to a similar model in 2022 after significant problems are
resolved in the terrestrial data holdings used to make the models. The impact on
Canadian regions is minimal but much more profound for regions in the U.S.A
because of the aerogravity coverage. Aerogravity flights continue over the Great
Lakes region to resolve some of these issues in the border region to ensure that
these are more likely available for the generation of CGG2013 and the impending
IGLD15 update. Aerogravity profiles have already been released for the Gulf
Coast region and preliminary analysis does show that the cm-geoid is achievable
for coastal regions.
|
Download (ppt) (5.95 MB)
|
A New Approach for New Datums (lightning talk)
|
Ronnie Taylor
|
Ronnie Taylor
|
|
2012/07/22
|
San Diego, CA
|
Survey Summit (the ACSM annual conference)
|
datums, geometric datum, geopotential datum, vertical datum, gravity, grav-d
|
|
Download (ppt) (7.45 MB)
|
Geoid improvement over Alaska/Yukon area by GRACE and GOCE models
|
Yan Ming Wang
|
Xiaopeng Li
|
|
2012/03/26
|
Vinna, Austria
|
EGU
|
geoid, satellite gravity model
|
|
Download (pptx) (2.57 MB)
|
GEOID12/GEOID12A
|
Yan Ming Wang
|
Yan Ming Wang
|
|
2012/10/25
|
Fair Oaks, Fairfax, VA
|
GeoTech 2012
|
geoid
|
|
Download (ppt) (20.55 MB)
|
Data fusion for geoid computation – numerical tests in Texas area
|
Yan Ming Wang
|
Yan Ming Wang
|
Xiaopeng Li
|
2012/10/10
|
Venice, Italy
|
International Symposium on Gravity, Geoid and Height Systems
|
geoid, method of optimal combination
|
|
Download (ppt) (2.99 MB)
|
A Comparison of topographic effect by Newton’s integral and high degree spherical harmonic expansion – Preliminary Results
|
Yan Ming Wang
|
Yan Ming Wang
|
S. Holmes, J Saleh, XP Li and D Roman
|
2010/06/22
|
Taipei, Taiwan
|
WPGM 2010
|
topography, gravity, spherical harmonic expansion
|
|
Download (pptx) (9.28 MB)
|
Absolute Heights and the Elusive 1 cm Geoid
|
Dru Smith
|
Dru Smith
|
|
2007/09/11
|
Washington, D.C.
|
NRC - National Academies' Mapping Science Committee Meeting
|
Height, Datum, Geoid
|
|
Download (ppt) (3.22 MB)
|
Confirming 1 cm differential geoid accuracy: The Geoid Slope Validation Survey of 2011
|
Mark Eckl
|
Dru Smith
|
Simon Holmes, Xiaopeng Li, Sébastien Guillaume, Yan Wang, Beat Bürki, Dan Roman, Mark Eckl
|
2012/10/11
|
Venice, Italy
|
GGHS -- IAG's International Gravity Field Service
|
Height, Datum, Geoid
|
|
Download (pptx) (7.72 MB)
|
Converting GPS Height into NAVD 88 Elevation with the GEOID96 Geoid Height Model
|
Dru Smith
|
Dru Smith
|
Dennis Milbert
|
1996/11/20
|
Denver, CO
|
GIS/LIS 1996
|
Geoid, Height, Datum
|
|
Download (pdf) (3.16 MB)
|
A New High Resolution Gravimetric Geoid Model for the United States Using the EGM96 Potential Coefficient Model
|
Dru Smith
|
Dru Smith
|
Dennis Milbert
|
1996/12/16
|
San Francisco, CA
|
AGU
|
Geoid, Height, Datum, EGM96
|
|
Download (pdf) (1.48 MB)
|
North American Geoid Computations Status Report
|
Dru Smith
|
Dru Smith
|
|
1997/08/01
|
Columbus, OH
|
North American Geoid Committee
|
Geoid, Height, Datum, GEOID96
|
|
Download (pdf) (2.83 MB)
|
The Impact of Different Satellite Altimeter Gravity Anomaly Data Sets on Geoid Height Models
|
Dru Smith
|
Dru Smith
|
|
1997/12/08
|
San Francisco, CA
|
AGU
|
Geoid, Height, Datum, Altimetry
|
|
Download (pdf) (5.08 MB)
|
Various Geoid Issues at NGS
|
Dennis Milbert
|
Dru Smith
|
Dennis Milbert
|
1998/04/01
|
Ottawa, Canada
|
Geodetic Survey Division
|
Geoid, Height, Datum, Altimetry, DEM, FFT
|
|
Download (pdf) (3.46 MB)
|
The CARIB97 High Resolution Geoid Height Model for the Caribbean Sea
|
Dru Smith
|
Dru Smith
|
Howard Small
|
1998/08/18
|
Silver Spring, MD
|
North American Geoid Committee
|
Geoid, Height, Datum, Altimetry, CARIB97
|
|
Download (pdf) (1.42 MB)
|
Geoid Computation Difficulties in the Pacific Northwest
|
Dru Smith
|
Dru Smith
|
|
1998/08/18
|
Silver Spring, MD
|
U.S. Geoid Committee
|
Geoid, Height, Datum, Altimetry, DEM, Terrain Correction
|
|
Download (pdf) (2.25 MB)
|
Localized Impacts Very-High Resolution Digital Elevation Data on Geoid Modeling
|
Dru Smith
|
Dru Smith
|
|
1999/05/10
|
Banff, Alberta, Canada
|
Canadian Geophysical Union
|
Geoid, Height, Datum, Altimetry, DEM, Terrain Correction
|
|
Download (pdf) (3.09 MB)
|
Reducing the Impact on the Geoid of Systematic Errors in the DEM and Computational Approximations in Terrain Reductions
|
Dru Smith
|
Dru Smith
|
|
1999/06/02
|
Boston, MA
|
AGU
|
Geoid, Height, Datum, Altimetry, DEM, Terrain Correction
|
|
Download (pdf) (2.87 MB)
|
Recent Advances in the Acquisition and Use of Terrain Data for Geoid Modeling over the United States
|
Dru Smith
|
Dru Smith
|
|
1999/07/23
|
Birmingham, UK
|
IUGG
|
Geoid, Height, Datum, Altimetry, DEM, Terrain Correction
|
|
Download (pdf) (3.08 MB)
|
Orthometric Heights from GPS and the GEOID99 high resolution geoid model for the United States
|
Dru Smith
|
Dru Smith
|
Dan Roman
|
1999/09/16
|
Nashville, TN
|
ION
|
Geoid, Height, Datum, GEOID99
|
|
Download (pdf) (1.20 MB)
|
Using GEOID99 and GPS to Determine Orthometric Heights in the United States
|
Dru Smith
|
Dru Smith
|
Dan Roman
|
1999/10/19
|
Tsukuba, Ibaraki, Japan
|
GPS99
|
Geoid, Height, Datum, GEOID99
|
|
Download (pdf) (2.04 MB)
|
NAVD 88 Helmert Orthometric Heights from NAD 83 GPS heights and the GEOID99 high resolution geoid height model
|
Dru Smith
|
Dru Smith
|
Dan Roman
|
2000/03/21
|
Little Rock, AR
|
ACSM
|
Geoid, Height, Datum, GEOID99
|
|
Download (pdf) (2.32 MB)
|
Recent Research at The National Geodetic Survey: The Geoid Slope Validation Survey of 2011
|
Dru Smith
|
Dru Smith
|
|
2012/11/14
|
URI (11/14/2012) and UNH (11/16/2012)
|
University of Rhode Island Coastal Institute and University of New Hampshire JHC/CCOM
|
NGS, Geodesy, Heights, GSVS11
|
Show Abstract
The United States National Geodetic Survey (NGS) has embarked on a ten year
project called GRAV-D (Gravity for the Redefinition of the American Vertical
Datum). The purpose of this project is to replace the current official
vertical datum, NAVD 88 (the North American Vertical Datum of
1988) with a geopotential reference system based on a new survey of the
gravity field and a gravimetric geoid. As part of GRAV-D, the National
Geodetic Survey plans to execute a set of "geoid validation surveys" at
various locations of the country. These will be surveys designed to
independently measure the geoid to provide a check against both the data and
theory used to create the final gravimetric geoid which will be used in the
geopotential reference system. The first of these surveys, known as the
Geoid Slope Validation Survey of 2011 (GSVS11) was executed between July and
October, 2011 in the west central region of Texas. The survey took place
over a 325 kilometer line running more or less north-south from Austin to
Corpus Christi, Texas. Measurements were taken at 220 marks (one per mile)
and included static GPS, RTN GPS, geodetic leveling, astro-geodetic
deflections of the vertical using the Swiss DIADEM camera, absolute gravity,
gravity gradients and LIDAR. This region was chosen for many factors
including the availability of GRAV-D airborne gravity over the area, its
relatively low elevation (220 meter orthometric height max), its geoid slope
(about 130 cm over 300 km), lack of significant topographic relief, lack of
large forestation, availability of good roads, clarity of weather and lack
of large water crossings. This talk will outline the results of the survey,
specifically the comparison of various geoid slopes over this region:
gravimetric geoid models (with and without airborne gravity), minimally
constrained GPS and leveling and from astro-geodetic deflections of the
vertical. In addition to a variety of interesting conclusions that came from
the multi-technique survey, GSVS11 conclusively proved that the addition of
recent GRAV-D airborne gravity data reduced the errors in gravimetric geoid
models in this region to 1 cm over all wavelengths from 0 to 325 km.
|
Download (pptx) (9.34 MB)
|
Datums and Tools to Connect Geospatial Data Accurately
|
Pamela Fromhertz
|
Pamela Fromhertz
|
|
2012/11/14
|
Colorado Springs, CO
|
Air Force Academy GIS Day
|
datums, GPS, GNSS, accuracy, NSRS, metadata, heights, OPUS, DS-World, GRAV-D, velocity
|
|
Download (pdf) (12.64 MB)
|
Rigorous Geodetic Positioning in the Americas
|
Neil D. Weston
|
Neil D. Weston
|
Tom Soler
|
2012/11/26
|
Montevideo, Uruguay
|
FIG
|
Positioning
|
|
Download (pdf) (0.79 MB)
|
Using and Understanding OPUS
|
Dan Martin
|
Dan Martin
|
|
2012/11/09
|
Holliston, MA
|
MALSCE Seminar
|
OPUS, OPUS-RS, GNSS, OPUS-DB
|
Show Abstract
The national Geodetic Survey (NGS) operates the On-line Positioning User Service
(OPUS) as a means to provide GPS users easier access to the National Spatial
Reference System (NSRS). OPUS allows users to submit their GPS data files to
NGS, where the data will be processed against the Continuously Operating
Reference Station (CORS) network to determine a position using NGS computers and
software. This seminar will discuss:
The history and development of OPUS products
A discussion of OPUS accuracies (and things that affect the accuracies)
Recommended collection procedures, data requirements, and data management
A discussion of how to use each of the OPUS products and how they work
An in-depth look at the output of OPUS and a discussion of OPUS statistics
and quality indicators
What can be done to make a poor solution better?
A discussion on datums and coordinate systems for OPUS
The recent CORS Multi-Year Solution and National Adjustment of 2011
|
Download (pptx) (106.81 MB)
|
Evolution of the National Spatial Reference System
|
Dan Martin
|
Dan Martin
|
|
2012/12/07
|
Concord, NH
|
NHLSA Annual Conference
|
NSRS, 10-year Plan, Datums, NA2011, Geoid
|
Show Abstract
In July of 2012, the National Geodetic Survey released the latest realization of
NAD 83 and a new companion geoid model. This presentation will discuss a brief
history of NAD 83, and reasons for its ongoing evolution. We will discuss the
data used to produce the National Adjustment of 2011 (NA2011), and the concept
(and need) to introduce velocities. Also discussed will be the relationships of
geoid models to various versions of NAD 83 and what can happen if these
relationships are ignored.
|
Download (pptx) (99.70 MB)
|
Kinematic GPS and Airborne Gravimetry Tutorial
|
Dr. Theresa Diehl
|
Dr. Theresa Diehl
|
|
2012/11/30
|
Pennsylvania State University, Wilkes-Barre Campus
|
Surveying Engineering 3rd-year students
|
vertical datum, airborne gravity, kinematic GPS, field work
|
Show Abstract
This is a formal presentation given for an hour at the start of a three-hour
tutorial on Kinematic GPS and airborne gravimetry to 3rd-year surveying
engineering students. The presentation focuses mostly on why and how NGS is
updating the vertical datum in 2022 to a gravimetric geoid, as well as the field
methodology used by GRAV-D to conduct large-scale airborne gravity campaigns
year-round.
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Download (ppt) (20.00 MB)
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NGS' Current and Future Programs
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Dr. Theresa Diehl
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Dr. Theresa Diehl
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2012/11/30
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Pennsylvania State University, Wilkes-Barre Campus
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Surveying Engineering students of all levels
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NGS, 10 year plan, NSRS, datums, modernization, CORS, OPUS, shoreline mapping,
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Show Abstract
This is an overview of NGS' current projects and plans included in the draft
10-year plan, which will be effective in 2013. The presentation touches lightly
on all the major programs and responsibilities of NGS, with projections about
their futures.
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Download (ppt) (20.12 MB)
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Latest Advancements at the Geodetic Survey
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Juliana Blackwell
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Juliana Blackwell
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2013/01/15
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Washington, DC
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Transportation Research Board
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New Datums, Update of NAD83, Geoid12A, OPUS, GRAV-D, Geoid Slope Validation Study, CORS, NDGPS
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Download (ppt) (16.22 MB)
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NGS Tools and Products
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Pamela Fromhertz
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Pamela Fromhertz
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2013/01/24
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Golden, CO
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Central Chapter of the Professional Land Surveyors of Colorado
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NSRS, NAD83 (2011) Adjustment, New Data Sheets, Geoid 12A, Heights, OPUS, DS-World, GRAV-D
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Show Abstract
There are many changes occurring at NGS, including new ways to access the
National Spatial Reference System (NSRS). Pam Fromhertz, the CO State Geodetic
Advisor, will cover the basics of the latest development occurring in NGS
including the latest NAD 83 Adjustment (2011), the latest geoid model (12A), the
new datasheets, as well as the tools to access the NSRS, such as DS-World and
OPUS, particularly OPUS-DB. She will provide the status on heights in CO, CBLs
and CORS. These topics will be discussed in much more detail at her 4 hour
session at the PLSC Annual Survey Summit.
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Download (ppt) (51.09 MB)
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2013 Update of NGS Products, Geodetic Services and Tools
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Marti Ikehara
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Marti Ikehara
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2013/01/25
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Clovis, CA
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CSUF Geomatics Engineering student Conference
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CORS, OPUS, Coordinate changes, Geoid12A, Datasheet, Advisors, DSWorld, Education
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Show Abstract
The California geodetic advisor will give updates on some of NGS' more popular
programs, including the CORS network, OPUS, and DSWorld software. The adoption
of ITRF2008 for CORS coordinates, the shift to absolute antenna calibrations,
and the publication of NAD83(2011) geometric coordinates and GEOID12A are
explained. There will be a review of the Datasheet fields, including the absence
of accuracy orders, as well as clarification of textual metadata. In light of
increasing concerns about planning for Sea Level Rise, there will be a brief
primer on tidal datums and usage of VDATUM software, which incorporates geodetic
datums.
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Download (pptx) (12.54 MB)
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NGS Geodetic Tools and Education Services
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Marti Ikehara
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Marti Ikehara
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2013/02/07
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Sacramento
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CLSA Sacramento Chapter
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CORS, California, Geoid12A, Datum Tags, Datasheet, Advisors, Education, VDatum, DSWorld
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Show Abstract
Topics addressed include the doubling of NGS CORS in California in 2012, the
development of Geoid12A, summary of recent datum tags for CORS and passive
monuments, datasheet format changes,modification of the advisor program, and
NGS' opportunities for continuing education which include posted presentations,
recorded webinars, conference workshops and classroom training opportunities.
Short demonstrations of Vdatum and DSWorld software conclude the presentation.
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Download (ppt) (7.29 MB)
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Latest Improvements from NGS
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Pamela Fromhertz
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Pamela Fromhertz
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2013/02/06
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Loveland, CO
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Northern Chapter of the Professional Land Surveyors of Colorado
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NSRS, GPS, Datums, MetaData, Latest Adjustment NAD 83 (2011), Geoid 12A, New data Sheets, CORS, OPUS, DS-World, New Datums, Training
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Download (ppt) (31.86 MB)
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