[postgis-users] Adding to Spatial Ref Sys table

[Frank Warmerdam]

Craig Miller wrote:
> What is the "correct" way to add SRS definitions to the spatial_ref_sys
> table.
> 
> I noticed that ogr only inserts the srid and srtext fields.  Are the other
> fields required?  If they aren't required what is the proj4text field used
> for.  Does it just improve performance by removing the need to determine the
> proj4 string from the wkt string on the fly?

Craig,

As far as I know the WKT is just informative, and the proj4text is what is
actually used.  The OGR PG driver should be inserting the proj4text.  Without
it the SRS creation option in the OGR PG driver is basically useless.

If you file a bug on this, I'll try and get it fixed.

> I'm assuming that by populating the auth_name and auth_srid columns that I
> can essentially define a "shortcut" to my any new definitions that are
> created.  E.g. I could specify SPATIALMINDS as the authority, and start
> numbering SRS definitions at 1 and refer to it as SPATIALMINDS:1 just like I
> refer to EPSG:4329 in various places.

My take on this is that you should leave the auth_name and auth_srid blank
if the coordinate system isn't from EPSG or another standard authoritative
source.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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