[MetaCRS] Lambert zone II to WSG84 issue

[Martin Desruisseaux]

Hello Christian

I suggest that you try to fix the prime meridian value in the WKT that 
you provided. The current value is:

    PRIMEM["Paris", 2.33722917]

It should be:

    PRIMEM["Paris", 2.5969213]


The former is in degrees, while the later is in gradians. The WKT 
specification defined in document OGC 01-009 explicitly said that the 
PRIMEM unit of measurement shall be the one of the enclosing GEOGCS 
element, which is UNIT["grad", 0.01570796326794897] in this case (a 
copy-and-paste of this specification can be seen at [1]). However many 
implementations ignore this specification and unconditionally fix the 
unit of measurement to degrees, maybe because this point was unclear in 
an older specification (WKT in OGC 01-009 was itself derived from WKT in 
Simple Features if my memory serve me right, and I think that the later 
was unclear about units. I guess that Proj.4 WKT is derived from the 
later). For example ESRI too seems to interpret the units that way.

     Regards,

         Martin

[1] 
http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PRIMEM

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/metacrs/attachments/20131120/c28f3d4f/attachment.html>