Date:Tue, 16 Aug 2005 16:40:14 -0400
Reply-To:Subject Coordinates Discussion List <[log in to unmask]>
Sender:Subject Coordinates Discussion List <[log in to unmask]>
From:Joe Aufmuth <[log in to unmask]>
Subject:Re: Question on form of coordinates
Comments:To: Subject Coordinates Discussion List <[log in to unmask]>
The Alexandria project is a prime example of an integer field which will
allow a variable range search. Where as a leading "+" sign and 0 place
holder in MARC limits the records to character based searches. Therefore
additional programming would be required for any MARC catalog interface to
extract the integer values from the character set and then compare them
against a patron's request. It's not the most efficient method. I presume
at the time the change was made to accept some format of decimal degree
coordinates, a visual spatial catalog search engine was not envisioned.
While mapping international dateline spatial data is tricky, treating them
as a series of points is not a problem. If the bounding box column names
are well defined only 2 coordinate pairs are needed, I.E. Upper Left X,
Upper left Y , Lower Right X and Lower Right Y. By definition of a box any
system could read the UL and LR coordinates and calculate the remaining 2
corners. Or, the additional X,Y coordinates for LL and LR columns could be
included and calculated by a cataloging macro. If the points are treated as
a set of coordinates in a single field additional programming also would be
required to extract the integer values from the set.
Has anyone seen the Geographic Code Indexing thread on the Maps-L listserv.
Perhaps we can tie in those discussions with ours? I am not a cataloger and
have a very basic question: what does the 052 field offer in terms of format
(integer vs. character), indexing, searching, and reporting?
And one last larger question. What will come of our discussions? Where is
MARC headed in terms of compatibility with FGDC or other spatial metadata
standards? -- sorry if this is off the thread's topic, but it is another
major issue facing GIS Librarians and digital spatial data related to MARC
records. Will additional MARC fields for digital spatial metadata, be
created? Will existing field formats be changed from character based to
integer based to enhance searching? What is the long term vision for MARC
and spatial metadata? My focus is rather biased towards digital spatial
data indexes and metadata search engines for our patrons.
Sorry to ramble on
George A. Smathers Libraries
University of Florida
P.O. Box 117001
Gainesville, Florida 32611-7001
[log in to unmask] <mailto:[log in to unmask]>
From: Subject Coordinates Discussion List [mailto:[log in to unmask]]On
Behalf Of Rebecca S. Guenther
Sent: Tuesday, August 16, 2005 10:06 AM
To: [log in to unmask]
Subject: Re: [SUBCOOR] Question on form of coordinates
For the record, I thought I would mention that a few years ago we made
some changes to the MARC field that contains the structured form of
coordinates, field 034 (MARC also has a field for the human readable form,
field 255). Field 034 has separate data elements (subfields) for
westernmost, easternmost, northernmost and southernmost coordinates. We
changed it to allow for variable length values and to use either the form
Colleen asked about (e.g. N0421510) or decimal degree format (e.g.
+079.533265, etc.). At the time we made this change, we were told that
there was not a need to specify the format used, since the format is
easily recognized by the number of characters and the placement of the
^^ Rebecca S. Guenther ^^
^^ Senior Networking and Standards Specialist ^^
^^ Network Development and MARC Standards Office ^^
^^ 1st and Independence Ave. SE ^^
^^ Library of Congress ^^
^^ Washington, DC 20540-4402 ^^
^^ (202) 707-5092 (voice) (202) 707-0115 (FAX) ^^
^^ [log in to unmask] ^^
On Mon, 15 Aug 2005, Archie Warnock wrote:
> 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
> > 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
> 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 Warnock [log in to unmask]
> -- A/WWW Enterprises www.awcubed.com
> -- As a matter of fact, I _do_ speak for my employer.