[OSGeo Africa] SRID

Gavin Fleming GavinF at mintek.co.za
Tue Feb 17 08:14:16 EST 2009

In PostGIS: SELECT * FROM spatial_ref_sys;

The only problem is, for SA projections like the LOs on Hartebeesthoek
datum, proj4 can't handle a south-facing projection (yet) and be aware
in PostGIS that while their EPSG codes are defined properly, the
matching proj4 strings are undefined (at 1.2 at any rate). 

I have some LO 27 data in PostGIS that QGIS and uDIG couldn't project,
yet GeoServer did. For the South African EPSG LO definitions to apply
though, you have to swap your x and y signs (though not the axes). 

A workaround in South Africa is to use normal Transverse Mercator on
Hartebeesthoek and standardise the axes and signs (i.e. make them look
conventional like the rest of the world) - then just define your own
EPSG (and proj4) code and add a record to PostGIS. 

Here's an Albers one I use a lot:

40000,EPSG,40000,PROJCS["South Africa Albers Equal Area
a +lat_1=-18 +lat_2=-32 +lat_0=0 +lon_0=24 +x_0=0 +y_0=0 +ellps=WGS84
+units=m +no_defs 


-----Original Message-----
From: africa-bounces at lists.osgeo.org
[mailto:africa-bounces at lists.osgeo.org] On Behalf Of Tim Sutton
Sent: 17 February 2009 13:57 PM
To: Africa local chapter discussions
Subject: Re: [OSGeo Africa] SRID


On Tue, Feb 17, 2009 at 12:10 PM,  <bartvde at osgis.nl> wrote:
> Hi,
> SRID is an Oracle term so I assume you are talking about Oracle
> It's in a table called CS_SRS in the MDSYS schema:
> select * from MDSYS.CS_SRS
> Best regards,
> Bart
>> Hi All,
>> First posting!!!
>> Where can I get a list of SRID's.
>> Regards,
>> Clinton Papenfus
>> 0833767083

For a user friendly list of CRS's you can also click on the icon in
the bottom right corner of the QGIS window, and you will be presented
with a CRS list. Click on any CRS entry to see its proj4 definition.



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