Ticket #1611 (assigned defect)

Opened 1 year ago

Last modified 7 months ago

EPSG 8903 - PRIMEM - VALUE - UOM

Reported by: Philippe Assigned to: warmerdam (accepted)
Priority: normal Milestone: 1.6.0
Component: OGR_SRS Version: unspecified
Severity: normal Keywords: epsg prime meridian
Cc:

Description

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

Attachments

ocean_prime_meridian_8903.pdf (2.1 kB) - added by Philippe on 05/04/07 03:26:06.
Source of the attached PDF file : http://ocean.csl.co.uk/experimental/index.php

Change History

05/04/07 03:26:06 changed by Philippe

  • attachment ocean_prime_meridian_8903.pdf added.

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

05/04/07 11:19:46 changed by warmerdam

  • keywords set to epsg prime meridian.
  • status changed from new to assigned.
  • component changed from default to OGR_SRS.
  • milestone set to 1.4.2.

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!

06/21/07 13:49:05 changed by warmerdam

  • milestone changed from 1.4.2 to 1.5.0.

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"]]

12/11/07 10:05:34 changed by warmerdam

  • milestone changed from 1.5.0 to 1.6.0.