[postgis-users] OSGB to lat/long conversion

[Mark Cave-Ayland]

On Mon, 2007-09-24 at 00:29 +0100, Chris Jewell wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hi all,
> 
> I have a problem converting OSGB coordinates to lat/long coordinates.  Currently, my
> data exists in OSGB (SRID 27700), and I need to convert to WGS84 for inclusion in a KML
> file.  However, currently all the points turn out as approximately 100-200m from where
> I expect them to be.  Looking at the PROJ4 mailing list, it seems that there was some
> issue with the datum used for the conversion
> (http://lists.maptools.org/pipermail/proj/2006-May/002265.html).  This has been fixed
> in the latest version of PROJ4, which I downloaded, compiled, and installed.  However,
> this has not fixed my problem with PostGIS.  Do I have to modify the spatial_ref_sys
> table to use the new datum in PROJ4?  If so, how?
> 
> Many thanks,
> 
> Chris


Hi Chris,

Yes, you need to make sure you are using PROJ 4.5.0 and perform an
update on your spatial_ref_sys table to append the extra datum parameter
to the proj4text field - see
http://postgis.refractions.net/pipermail/postgis-users/2007-July/016525.html for more information.


HTH,

Mark.

-- 
ILande - Open Source Consultancy
http://www.ilande.co.uk