Date:         Mon, 15 Aug 2005 09:08:09 -0400
Reply-To:     Subject Coordinates Discussion List <[log in to unmask]>
Sender:       Subject Coordinates Discussion List <[log in to unmask]>
From:         Archie Warnock <[log in to unmask]>
Organization: A/WWW Enterprises
Subject:      Re: Question on form of coordinates
Comments: To: Subject Coordinates Discussion List <[log in to unmask]>
In-Reply-To:  <[log in to unmask]>
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Colleen R. Cahill wrote:
> As a map cataloger, I primarily deal with coordinates in two forms:
> human-readable geographic coodinates (i.e. North 42 degrees, 15 minutes,
> 10 seconds) and machine-readable decimal degrees (i.e. N0421510). For the
> proposed subject coodinates, a machine-readable form of coordinates is
> needed and so I always think of decimal coordinates.  This is form a
> standard used much?  Are there any other (better or worse) ways used to
> present coordinates?

Thanks for getting this started, Colleen.

Decimal degress are, I think, to be preferred in almost all cases
although there are certainly occasional needs for alternative coordinate
reference systems.  Decimal degrees are trivial for machines to parse,
they sort sensibly and are even relatively easy for humans to read.

Metadata standards, eg, the Z39.50 GEO Profile
(http://www.blueangeltech.com/standards/GeoProfile/geo22.htm), the FGDC
Content Standard for Digital Geospatial Metadata (CSDGM -
http://www.fgdc.gov/metadata/csdgm/), various OGC documents
(http://portal.opengeospatial.org/files/?artifact_id=1094,
https://portal.opengeospatial.org/files/?artifact_id=6716), to the
extent that they address spatial coordinates at all, require the use of
decimal degrees.

A bigger issue with geographic coordinates, it seems to me, is ensuring
that the coordinates are treated together, not as individual bounding
coordinates.  That is, a bounding rectangle needs to be considered as a
_set_ of 4 coordinates and handled together, rather than as 4
independent points.  Otherwise, footprints that cross the International
Date Line become much harder to handle.

--
Archie

-- Archie Warnock                         [log in to unmask]
-- A/WWW Enterprises                          www.awcubed.com
--       As a matter of fact, I _do_ speak for my employer.