[postgis-users] How to do inverse projection?

[Henri De Feraudy]

Thankyou Nicolas,
So you are telling me that the SRID of WGS84 is 4326 and that the coordinates of 
WGS84 are latitude and longitude? 
I'm going to use these resulting coordinates for the GoogleMaps api, and I am 
guessing that input to the latter can be WGS84.
Henri



________________________________
From: Nicolas Ribot <nicolas.ribot at gmail.com>
To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
Sent: Sun, January 23, 2011 12:31:44 PM
Subject: Re: [postgis-users] How to do inverse projection?

> 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
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