EPSG 8903 - PRIMEM - VALUE - UOM

[Philippe]

0 grad Paris = 2° 20' 14.025" = 2.33722917° = 2.5969123 grad E Greenwich So, in my opinion, PRIMEM["Paris",2.33722917,AUTHORITY["EPSG","8903"]] should rather read PRIMEM["Paris",2.5969213,AUTHORITY["EPSG","8903"]] as the UOM for PRIMEM 8903 is not degree but grad. Thanks Philippe

[Philippe]

Source of the attached PDF file : ​http://ocean.csl.co.uk/experimental/index.php

[warmerdam]

The problem would appear to be that the ogr_fromepsg.cpp code assumes that all prime meridians are in decimal degrees and just ignores the units set in EPSG. This needs to be fixed!

[warmerdam]

trary to my previous reading, the prime meridian is being converted from grads to degrees and 2.33... degrees is the right value for Paris.

So the only issue is whether, in fact, the angular units in PRIMEM ought to match the angular degree unit for the GEOGCS. Perhaps it should, but for now this is not negatively impacting GDAL/OGR. So, I am putting this off as a 1.5.0 issue.

Note, this issue can be demonstrated by expanding EPSG:4807:

WKT[EPSG:4807] =
GEOGCS["NTF (Paris)",
    DATUM["Nouvelle_Triangulation_Francaise_Paris",
        SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936265,
            AUTHORITY["EPSG","7011"]],
        TOWGS84[-168,-60,320,0,0,0,0],
        AUTHORITY["EPSG","6807"]],
    PRIMEM["Paris",2.33722917,
        AUTHORITY["EPSG","8903"]],
    UNIT["grad",0.01570796326794897,
        AUTHORITY["EPSG","9105"]],
    AUTHORITY["EPSG","4807"]]

[warmerdam]

remove non-serious milestone.milestone

[Jukka Rahkonen]

The WKT from EPSG:4807 is still the same as 7 years ago. Meanwhile it has obviously not bothered anybody seriously. I feel that closing this ticket would not do any big damage.

[Jukka Rahkonen]

Closing now.