Date:         Mon, 17 Jul 2006 10:38:30 -0700
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Sender:       Subject Coordinates Discussion List <[log in to unmask]>
From:         Mary Larsgaard <[log in to unmask]>
Organization: UCSB Map & Imagery Lab, Library
Subject:      Re: coordinates in decimal degrees or in degrees/minutes/seconds
Comments: To: Subject Coordinates Discussion List <[log in to unmask]>
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It seems to me this comes down to
a practical matter of what form
a trusted source has these in -
if we can get a set of bounding-box
coords for each country, each U.S.
state (and of course states for other
countries) and each U.S. county,
and they're in decimal degrees,
then that's the way they are.
As noted, it's easy from a computer-software
point of view to convert from one to the other.
The only cautionary note I would
sound is that when one converts
degrees/m/s coordinates to decimal
degrees, one may need 10 or 12
decimal points in order to make
sure it's the same number.
(I found this out the hard way
when I was writing a procedure
for catalogers who didn't have
access to the Web to convert
d/m/s to decimal and vice versa,
using a calculator - when I had
coordinates that were odd -
e.g., W 17d 21 m 43 s - 8
decimal points wasn't enough
to enable me to convert back
to the original dms # from the decimal degrees).

Mary

Colleen Cahill wrote:

>Paige Andrew wrote:
>
> As to the accuracy of a set of coordinates, of course that depends on the
>source and I believe (Colleen, help me out here) that we are going to rely
>on data primarily from trusted sources such as GNIS and GEOnet, but also are
>gathering datasets from ESRI and other like institutions.
>
>---------------
>
>Paige is correct that coordinate data will need to come from trusted
>sources, but there are some that might be constrained from offering their
>data.  Since the Broad of Geographic Names is the body that establishs the
>US officially recognized name for foreign places, they would hestitate to
>give bounding box coordinates as this could be constrused to mean the
>coordinates had some legal US definition of borders.  It would also be
>possible for coordinates to be added by the cataloger who is creating the
>authority record an in some cases, this might be the best source for that
>data, as they could have access to local information. If they are trusted to
>establish the name, why not the coordinates, if easily found?
>
>One thing to keep in mind is these are thematic coordinates, not legally
>bindings ones.  Like any authority data, they can be updated and corrected
>as needed. Since their primary purpose is for subject searching, the
>question of who is an authority needs to be tempered with that.  And for
>historical data, we are likely to have to look beyond GNIS, focuses on
>current coordinate information. 
>
>Colleen 
>  Colleen R. Cahill                   |  [log in to unmask]
> Digital Production Coordinator      |  (202)707-8540
>  & Recommending Officer for         |  FAX (202)707-8531
>       Science Fiction & Fantasy     |  Library of Congress
>These opinions are mine, Mine, Mine! |  Washington, DC 20540-4652
>  
>


-- 
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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