Ticket #32 (closed defect: fixed)
A deprecated datum shift has been listed as preferred by datum_shift_pref.csv.
|Reported by:||mikrit||Owned by:||warmerdam|
I noticed that the current gcs.csv entry for EPSG:4313 (Belge 1972) is
4313,Belge 1972,6313,Reseau National Belge 1972,6313,9122,7022,8901,1,0,6422,15749,1,9607,-106.8686,52.2978,-103.7239,-0.3366,0.457,-1.8422,1.2747
(taken from http://svn.osgeo.org/metacrs/geotiff/trunk/libgeotiff/csv). This means that the datum shift EPSG:15749 is used. But this datum shift was deprecated in March 2007, and replaced by EPSG:15929. Reason: "Error in sign of dS parameter value" (It should be -1.2747).
In general, some deprecated datum shifts can be quite useful. Because EPSG has sometimes deprecated an entire datum (and all associated datum shifts) for a trivial reason, like a spelling error in the name of the datum. In these cases, if you have old data files tagged with the deprecated datum code, it is useful if the datum shift remains in gcs.csv. (It wouldn't remain if all deprecated datum shifts are discarded when generating gcs.csv).
Unfortunately, I don't know any clever way to distinguish the harmful deprecated datum shifts from the useful ones. (Except by manual inspection, of course.)