[MetaCRS] Lambert zone II to WSG84 issue

[Christian Gendreau]

Hi Martin,

Thanks for your answer.

I can confirm that using PRIMEM in gradians I'm getting :
POINT (2.4173355764792475 48.83520898436396)
Which seems to be exact.

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.

Thanks again,

Christian

On Wed, Nov 20, 2013 at 8:34 AM, Martin Desruisseaux
<martin.desruisseaux at geomatys.fr> wrote:
> 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
>
>
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-- 
Christian Gendreau ing. jr
Ingénieur logiciel / Software Engineer
Canadensys - www.canadensys.net

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Email: christian.gendreau at umontreal.ca