Projection WGS84 in decimal degree

[Frank Warmerdam]

On 1/12/06, zze-SIGALE PORTANERI F ext RD-BIZZ-SOP
<fportaneri.ext at rd.francetelecom.com> wrote:
> Hi Frank & Ed,
>
> Thanks for your prompt and efficient answers!!!
>
> You're right, the pbm seems to come from the prime meridiam mismatch (and not decimal degree conversion issue as I thought before).
> I was able to confim this by manually doing some conversion tests using the Convers useful little tool (http://vtopo.free.fr/convers.htm ).
>
> As per example, for a WGS84 GPS point in Paris: longitude=2.38388   latitude=48.85562
>
> In Lambert II Etendu, I have today (wrong value) : X=775063.135566471  Y=2431242.54750943
> which is given using "Paris" as origin in Convers and which corresponds to the postgis transform call :
>
>   psql> select public.transform(GeometryFromText('POINT (2.38388 48.85562)',  4326), 27582);
>    SRID=27582;POINT(775063.135566471 2431242.54750943)
>
> So I have to find other EPSG values to get the correct X/Y that should be:
> X=603478.33780249   Y=2428587.76696934.
>
> I didn't find it yet, but I keep investigating in the spatial_ref_sys postgis (0.9.1) table!!!

FP,

I think what you will need to do is correct the PROJ.4 definition
in the spatial_ref_sys table.  If you examine the +pm and +lon_0
settings you should be able to adjust things.  Generally
the problem generating the proj.4 was that the +pm setting
was made *and* the +lon_0 was offset by the prime meridian
(or something like that).

Best regards,
--
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