VEP-017.txt

Vocabulary: http://www.ivoa.net/rdf/refframe
Author: Markus Demleitner <msdemlei@ari.uni-heidelberg.de> and J.J. Kavelaars
Date: 2024-11-17

New Term: geo_app
Action: Modification
Label: Geocentric Apparent Positions
Description: Positions given as observed by a fictitious observer at the
	Earth’ s centre for the equator of observation.
Relationships: narrower than #EQUATORIAL
Used-in: VOTable legacy

Rationale:
When the legacy VOTable terms were added to the refframe vocabulary
(which was necessary to keep validity criteria when VOTable changed
COOSYS/@system to being controlled by this vocabulary), nobody rememberd
what geo_app might have meant.  It recently turned out that it must
have been “Geocentric Apparent”, a frame used primarly in geodesy and
solar system science.  It is documented to some extent in
https://starlink.eao.hawaii.edu/docs/sun211.htx/sun211ss454.html.

This VEP replaces label, description, and relationship for the concept.
At this point, this is a deprecated concept, and since it is mixing
refposition and frame ("geocentre" vs. "apparent positions at equator of
epoch"), we quite certainly won't want anyone to use it.  We still want
to update the concept metadata and hence ask for exemption from the
“must be used somewhere” rule.

Reference:
- Calabretta and Greisen, AA, 2002, doi:10.1051/0004-6361:20021327