[postgis-users] How to do inverse projection?

[Nicolas Ribot]

> Hi,
>   I'm a bit naIve when it comes to this stuff about projections and
> coordinates.
> Suppose I have data that have been projected with a particular system (i
> suppose the SRID determines which projection it is)
> How do I get the inverse projection in terms of latitude and longitude of a
> point from the point's coordinates in the projection?
> Is there a general function for that in PostGis?
> Thanks
> Henri

Hi,
Use st_transform(geometry, srid)
(http://postgis.org/documentation/manual-1.5/ST_Transform.html), for instance:

(A point in french projection, srid=2154, tranformed to WGS84, srid=4326 ) :
select st_transform(st_geomFromText('POINT ( 576376 6265916)', 2154), 4326);

Nicolas