Date:         Tue, 18 Jul 2006 09:25:48 -0700
Reply-To:     [log in to unmask]
Sender:       Subject Coordinates Discussion List <[log in to unmask]>
From:         Mary Larsgaard <[log in to unmask]>
Organization: UCSB Map & Imagery Lab, Library
Subject:      Re: elevation in authority records
Comments: To: Subject Coordinates Discussion List <[log in to unmask]>
In-Reply-To:  <[log in to unmask]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Not that I'm suggesting we race off
and write yet another MARBI proposal
to include fields for elevation in 034:-)
It's just once Joe suggested this,
I felt kinda dumb for not thinking
of it myself. So I started to turn
around in my mind how this might
be done:
As i visualize it, there would have to the option
to have an elevation subfield for each lat/long pair
and there would have to be a way to associate
the correct elevation with the correct lat/long pair.

Maybe it would work like 034 |s and |t -
the long and lat for each vertex
of a non-bounding-box polygon; the software
"knows" that when there is a string of
|s followed by |t, followed by another |s and
another |t, and so forth, that each s is related
to one, and only one, |t.

Perhaps something like
034    |d |f |subfield for elevation |d |g |subfield for elevation |e |f 
|subfield for elevation |e |g  |subfield for elevation

and then for vertices of polygons, it would be:
|s |t |subfield for elevation |s |t |subfield for elevation |s |t 
|subfield for elevation [etc.]

Mary

Joe Aufmuth wrote:

>Hi Paige,
>
>Hope all is well.  Its been a long time since we talked.
>
>"What we are after is identifying the geographical location of a place on the Earth's surface via a set of coordinates, and what has been proposed is that this can be done as a bounding box, as X,Y point coordinates, or as a polygon. This is the same as what we are able to provide in the MARC format for bibliographic records so their is nothing new here." 
>
>Your statement is a great description.  This is what I also understood as the basis for the proposal.  Elevation (as Dean mentioned) and time/date also are an important component of spatial analysis.  If we could find a way to include them in searchable subfields it would be useful too.
>
>"If coordinate values vary that much from one type of GPS unit to the other (I find that a bit 
>surprising since these units are downloading information from the same 
>satellites, is that right?)"  
>
>Even though a common ephemeris may be used, a lot of GPS accuracy is based upon the clock used in the GPS receiver, and the number of channels each receiver has.  The more expensive receivers have more accurate clocks to measure the time to receive a signal (and thus determine distance to satellites) as well as having more channels to use in calculating position through trilateration.
>
>"Accuracy is certainly important for this data, but I wouldn't put the onus of testing said accuracy on catalogers"
>
>Agreed.  The only reason I brought it up is because I sensed from previous posts that catalogers may be out using GPS to collect coordinates for local authority records.  My point was, who ever collects original coordinates for a record should be able to make an accuracy statement about the coordinates collected.  How many people or organizations are in a position to do that?  How does one become an accepted local authority for catalog records?  
>
>"If the majority of the coordinate data comes from already-trusted sources such as the Board on Geographic Names then perhaps the accuracy issue will not be that big of a headache?"
>
>Correct.  Because BGN and other organizations are a recognized authority.  Granted, sometimes their information is wrong too.  Perhaps we need to determine how individuals or organizations can become the local authority for coordinates and place names -- I have never heard of any agreement on this topic when discussing gazetteers.  Because someone uses GPS to record a location does that make them a local authority?
>
>I am not a cataloger.  The only investment I have in this process is as a GIS user of the new coordinate fields.  My goal is to discuss the format of the fields created and how the data is collected and entered so that it will be useful for spatial/temporal search interfaces.
>
>Joe
>
>
>
>At 09:42 AM 7/3/2006, Joe Aufmuth wrote:
>  
>
>>If we're going to use GPS for authority records, what level of accuracy 
>>will be acceptable?  Will there be a standardized method of 
>>collection?  Typical handheld "walmart" receivers greatly vary in their 
>>measurements.  Elevations in particular can be quite poor.  So, who will 
>>be generating the authority records and the subsequent coordinates and 
>>elevations?  Surveyors?  GNIS?  NGA? Catalogers?  Who will be testing the 
>>accuracy of the coordinates used?
>>
>>Joe
>>
>>Joe Aufmuth
>>GIS coordinator
>>George A. Smathers Libraries
>>Government Documents
>>University of Florida
>>P.O. Box 117001
>>Gainesville, Florida 32611-7001
>>352-273-0367
>>Fax: 352-392-3357
>>[log in to unmask] <mailto:[log in to unmask]>
>>
>>
>>
>>
>>
>>-----Original Message-----
>>From: Subject Coordinates Discussion List [mailto:[log in to unmask]]On
>>Behalf Of Dean C Rogers
>>Sent: Friday, June 30, 2006 11:20 AM
>>To: [log in to unmask]
>>Subject: Re: [SUBCOOR] The proposal passed MARBI!
>>
>>
>>Yes, great. And since GPS includes elevation, so will the authority
>>records, right? (I hope).
>>
>>Dean Rogers
>>Map Cataloger
>>Library
>>U.S. Geological Survey
>>Reston, Va.
>>
>>
>>
>>"Houghton,Andrew" <[log in to unmask]>
>>Sent by: Subject Coordinates Discussion List <[log in to unmask]>
>>06/30/2006 07:49 AM
>>Please respond to
>>Subject Coordinates Discussion List <[log in to unmask]>
>>
>>
>>To
>>[log in to unmask]
>>cc
>>
>>Subject
>>Re: The proposal passed MARBI!
>>
>>
>>
>>
>>
>>
>>    
>>
>>>From: Subject Coordinates Discussion List
>>>[mailto:[log in to unmask]] On Behalf Of Colleen R. Cahill
>>>Sent: 30 June, 2006 07:15
>>>To: [log in to unmask]
>>>Subject: [SUBCOOR] The proposal passed MARBI!
>>>
>>>We now face some choices, primarly in what format we want the
>>>coordinates to appear in authority records.  This can be
>>>either degrees, minutes, seconds or decimal degrees: both
>>>have advantages and disadvantages. Here are a few I have
>>>thought of and am hoping for your input:
>>>
>>>Degrees, minutes, seconds format
>>>Pro:
>>>-Format most often printed on maps
>>>-Familiar to most people
>>>-Easy to quality review
>>>-Format most often used in bib records
>>>
>>>Con:
>>>-Not format used by GIS search engines
>>>
>>>Decimal Degrees
>>>Pro:
>>>-Format used by GIS search engines
>>>-Can harvest data from GIS tools
>>>
>>>Con:
>>>-Not as easy to quality review
>>>-Not as familiar a format to the average person
>>>      
>>>
>>Handheld GPS devices can output either format and output from
>>the GPS device may be used to create local authority records.
>>In addition, the conversion between decimal degrees and DMS
>>is trivial.  If the catalog uses decimal degrees, it can be
>>easily converted to DMS for user friendly displays.  This
>>point negates Con(2) under Decimal Degrees.
>>
>>I'm not throwing my two cents either way, just providing a
>>few additional thoughts.  So long as the data is in its own
>>subfield and it doesn't need to be parsed out of other textual
>>data, then either format can be used effectively.
>>
>>
>>Andy.
>>
>
>  
>


-- 
Mary Lynette Larsgaard
Director, Map Library
Assistant Head, Map and Imagery Laboratory
Davidson Library
University of California, Santa Barbara
Santa Barbara CA 93106-9010
USA
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voice: 805/893-4049; 2779, reference desk
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