[MetaCRS] Lambert zone II to WSG84 issue

[Martin Desruisseaux]

Hello Christian

Le 20/11/13 11:05, Christian Gendreau a écrit :
> I can confirm that using PRIMEM in gradians I'm getting :
> POINT (2.4173355764792475 48.83520898436396)
> Which seems to be exact.
Thanks for the confirmation.

> So my next question is, how can I be aware of that?
> There is no unit directly associated with PRIMEM and the definition of
> spatialreference.org
> (http://spatialreference.org/ref/epsg/27572/ogcwkt/) is using degrees.
The only way I can imagine is to be aware of who is the WKT producer, 
and adapt accordingly:

  * If the producer is GDAL, PostGIS or ERSI, then units are degrees.
  * If the producer is GeoTools, Apache SIS or Cadcorp (I presume, since
    they are the spec. author), then units are those of the enclosing
    GEOGCS element.
  * I don't know for Oracle WKT...


Frank Warmerdam wrote a page of WKT issues at [1]. Some of the 
variations that we observe in WKT interpretations are also listed at 
[2]. Those problems are one of the main motivations why OGC/ISO started 
a "WKT 2" effort. A "WKT 2" specification is close to final stage and is 
expected to be available as the international standard ISO 19162. It 
would hopefully solve the problems that we currently see with WKT 1.

     Martin

[1] http://home.gdal.org/projects/opengis/wktproblems.html
[2] 
https://builds.apache.org/job/sis-jdk7/site/apidocs/org/apache/sis/io/wkt/Convention.html#OGC

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