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eden_dem_cm_nov07.nc

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Frequently-anticipated questions:


What does this data set describe?

Title: eden_dem_cm_nov07.nc
Abstract:
This is the 1st release of the third version of an Everglades Depth Estimation Network (EDEN) digital elevation model (DEM) generated from certified airborne height finder (AHF) and airboat collected ground surface elevations for the Greater Everglades Region. This version includes all data collected and certified by the USGS prior to the conclusion of the AHF collection process. It differs from the previous elevation model (EDEN_EM_JAN07) in that the modeled area of WCA3N (all the WCA3A area north of I-75) is increased while the modeled area of the Big Cypress National Preserve (BNCP) has been both refined and reduced to the region where standard error of cross-validation points falls below 0.16 meters. EDEN offers a consistent and documented dataset that can be used to guide large-scale field operations, to integrate hydrologic and ecological responses, and to support biological and ecological assessments that measure ecosystem responses to Comprehensive Everglades Restoration Plan. To produce historic and near-real time maps of water depths, the EDEN requires a system-wide DEM of the ground surface.

This file is a modification of the eden dem released in October of 2007 (i.e., eden_em_oct07) in which the elevation values have been converted from meters (m) to centimeters(cm) for use by EDEN applications software. This file is intended specifically for use in the EDEN applications software. Aside from this difference in horizontal units, the following documentation applies.

  1. How should this data set be cited?

    Kevin Chartier John Jones, 200711, eden_dem_cm_nov07.nc.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -81.363536
    East_Bounding_Coordinate: -80.22176
    North_Bounding_Coordinate: 26.683613
    South_Bounding_Coordinate: 25.229604

  3. What does it look like?

    <http://sofia.usgs.gov/eden/models/groundelevmod.php> (php)
    graphic showing the coverage of EDEN_EM_OCT07

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 1995
    Ending_Date: 2007
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: raster digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: Greater Everglades region
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 402 x 284 x 1, type Grid Cell

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 17
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -81
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000
      False_Northing: 0

      Planar coordinates are encoded using Row and Column
      Abscissae (x-coordinates) are specified to the nearest 400
      Ordinates (y-coordinates) are specified to the nearest 400
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 1
      Altitude_Distance_Units: centimeters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    The CF-compliant metadata in the header of the NetCDF file provides spatial information for projecting the data into a GIS as well as the start date and time step for the time-series of data in the file. It also provides information about the conventions used for attributes in the dataset and the source software used to create the dataset.
    Entity_and_Attribute_Detail_Citation:
    NetCDF Climate and Forecast (CF) Metadata Conventions, Version 1.0, 28 October, 2003 at <http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.0/>


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    Kevin Chartier
    University of Florida
    3205 College Avenue
    Davie, FL 33314-7719

    954 577-6382 (voice)
    kchart@ufl.edu


Why was the data set created?

These data were specifically created for the development of water depth information using interpolated water surfaces from the EDEN stage data network.


How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: 2007 (process 1 of 2)
    The EDEN domain was broken into a large number of equal-sized rectangles (cells) that in total are referred to as the "grid". Characteristics of this grid, such as location of the centroid, the representative area of the Everglades, elevation, and percentage of vegetation type, define the grid spatial parameters. To match the Airborne Height Finder (AHF) data sampling spacing, the spatial resolution or the dimension (in ground distance) of each grid cell is 400 meters on each side. The ground surface DEM development process is iterative as additional high accuracy elevation data (HAED) are collected, water surfacing algorithms improve, and additional ground-based ancillary data become available. The DEMs used in the EDEN analysis through the summer of 2006 rely on version HAEDbeta2 of HAED. However, this version was produced by using all available AHF points posted to SOFIA as of August 2007. To create a realistic region-wide elevation model for EDEN purposes, the elevation data were segregated by Water Conservation Areas and National Park boundaries so that local trends could be isolated, sub-region specific interpolation models could be developed, and realistic breaks in elevation along sub-region boundaries could be imbedded in a final, region-wide DEM, To date the best performing DEMs for all subareas have been produced using the geostatistical approach called "anisotropic ordinary kriging". The latest iteration of the EDEN DEM used in EDEN applications is referenced as eden_em_oct07.

    Person who carried out this activity:

    John Jones
    U.S. Geological Survey
    Project chief
    521 National Center
    Reston, VA 20192
    USA

    703 648-5543 (voice)
    703 648-4165 (FAX)
    jwjones@usgs.gov

    Date: Nov-2007 (process 2 of 2)
    The DEM with elevations in meters was converted to a NetCDF file with the elevations in centimeters for use with the EDENapps. The conversion was done with JEM NetCDF writer software.

    Person who carried out this activity:

    Kevin Chartier
    University of Florida
    3205 College Avenue
    Davie, FL 33314-7719

    954 577-6382 (voice)
    kchart@ufl.edu

  3. What similar or related data should the user be aware of?

    Telis, Pamela, 2006, The Everglades Depth Estimation Network (EDEN) for support of ecological and biological assessments: USGS Fact Sheet 2006-3087, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

    Jones, J. W., 2001, Image and in situ data integration to derive sawgrass density information for surface-flow modeling in the Everglades: International Association of Hydrological Sciences, Wallingford, Oxfordshire, UK.

    Other_Citation_Details:
    in Remote Sensing and Hydrology 2000, editors Manfred Owe, Kaye Brubaker, Jerry Ritchie, and Albert Rango, publicaton 267, ISBN 1-901502-46-5
    Desmond, G. B., 2003, Measuring and mapping the topography of the Florida Everglades for Ecosystem Restoration: USGS Fact Sheet 021-03, U.S. Geological Survey, Reston, VA.

    Online Links:


How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    Horizontal positions are established by GPS observations and are referenced to the North American Datum of 1983 (NAD83). The desired horizontal accuracy is +/- 15 centimeters. This level of accuracy is consistent with GPS differential techniques which use two stations - a high-quality dual-frequency GPS receiver base station and a roving GPS station. The density and accuracy of a given GPS data observation varies from a few meters to a few centimeters according to the Position Dilution of Precision (PDOP) in the study area. Generally if the PDOP is observed to be excessive, data collection is discontinued or the data are discarded. The PDOP is an indicator of the positional accuracy of the GPS that be can derived from the current GPS satellite geometry, which varies continuously. Generally the smaller the PDOP number, the higher the data quality. The PDOP is a permanent part of the recorded data and is also included in the post processing procedures during reduction of the GPS observations to NAD 83. Where possible, the GPS base station has an ellipsoid height to an accuracy of two centimeters relative to the Continuously Operating Reference Stations (CORS) or the High Accuracy Reference Network (HARN), both operated by the National Geodetic Survey (NGS).

  3. How accurate are the heights or depths?

    Source data (HAED) collected to better than +/- 15cm. Standard errors of cross-validation for the DEM range from ~7cm to 17cm depending on the EDEN subarea. This version is composed of new models created for WCA3N and the BCNP combined with the mosaic of two versions (i.e., eden_v002a for WCA1 and eden_v002c for all other EDEN subregions) that comprised EDEN_EM_JAN07. The previous mosaic was selected based on analysis of model performance in the water depth estimation process. The WCA1 surface was produced by removing all "upland" AHF points as defined by a reclassification of the Florida GAP process. For WCA1, the krigging model was developed based on statistics from the entire EDEN domain (the process for eden_v002a production). For each other EDEN sub-area (i.e., the other WCAs and the National Park) region specific krigging models were developed and applied.

  4. Where are the gaps in the data? What is missing?

    Ground-surface elevation data were collected by the USGS at more than 50,000 points with an approximate spacing of 400 meters covering almost the entire Greater Everglades. The EDEN water-level network consists of hourly water-level data from 253 gaging stations (230 existing gaging stations and 23 new installations) and includes freshwater (nontidal) marsh gaging stations, boundary gages on canals, and coastal gaging stations operated by the Big Cypress National Preserve (BCNP), Everglades National Park (ENP), South Florida Water Management District (SFWMD), and USGS. The U.S. Army Corps of Engineers (USACE) and SFWMD recently documented or surveyed a majority of the hydrologic gages in the Greater Everglades to obtain correct values for converting water-level data from NGVD 29 to NAVD 88. The NAVD 88 datum is consistent in comparing water-level data across the Greater Everglades and computing accurate water depths.

  5. How consistent are the relationships among the observations, including topology?

    The EDEN monitoring network includes ground-elevation measurements and continuous water-level data.


How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
These data were produced for EDEN operational water depth estimation and applications.
Use_Constraints:
The user is cautioned that this elevation model was produced specifically for EDEN applications and is based on input data of approximately 400m sample spacing and +/- 15cm vertical accuracy. No statement of appropriateness for uses other than that intended are implied.

  1. Who distributes the data set? (Distributor 1 of 1)

    Heather S.Henkel
    U.S. Geological Survey
    600 Fourth St. South
    St. Petersburg, FL 33701
    USA

    727 803-8747 ext 3028 (voice)
    727 803-2030 (FAX)
    hhenkel@usgs.gov

  2. What's the catalog number I need to order this data set?

    EDEN DEM in centimeters

  3. What legal disclaimers am I supposed to read?

    The data have no explicit or implied guarantees.

  4. How can I download or order the data?


Who wrote the metadata?

Dates:
Last modified: 20-Nov-2007
Metadata author:
Heather Henkel
U.S. Geological Survey
600 Fourth Street South
St. Petersburg, FL 33701
USA

727 803-8747 ext 3028 (voice)
727 803-2030 (FAX)
sofia-metadata@usgs.gov

Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


This page is <http://sofia.usgs.gov/metadata/sflwww/eden_dem_cm_nov07_nc.faq.html>

U.S. Department of the Interior, U.S. Geological Survey
Comments and suggestions? Contact: Heather Henkel - Webmaster
Generated by mp version 2.8.18 on Wed Nov 21 15:30:59 2007