[postgis-users] Datum Change

[Armin Burger]

Jaime,

you need to add the parameters for the datum shift to your 
spatial_ref_sys table in the proj4text field as '+towgs84=' parameter 
for all projections where you want to have the datum shift. I guess the 
reason why these parameters are not added by default is that you can 
have different sets per projection system, depending on the region.

A short list for some projections is available at
http://freegis.org/cgi-bin/viewcvs.cgi/*checkout*/grass/src/libes/gis/datumtransform.table

for Europe you can find parameters eg. at
http://crs.bkg.bund.de/crs-eu/

And the EPSG database (at www.epsg.org) has also a bigger set of those 
parameters. There was once a posting of somebody on this list providing 
additional tables and views to extract the information from the EPSG tables.

Armin

jaime villanueva wrote:
> Hi list users
> 
> How can i make Datum transformations with postgis?
> 
> i have tried with transform function, with diferents SRID's, but the 
> reproyection works fine (transform() function using srid's with the same 
> datum), but the transformation between different DATUMS give me wrong 
> coordinates.
> 
> Regards
> 
> 
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