[postgis-users] transform() does not do work for NGO1948 zone III -> WGS84 longlat (epsg:27393->epsg:4326)

[strk at refractions.net]

On Tue, Dec 20, 2005 at 04:46:16PM -0000, Mark Cave-Ayland wrote:
...
> Actually, looking through the source lwgeom_transform.c I see the following
> comment around line 500:
> 
> //this is *exactly* the same as PROJ.4's pj_transform(), but it doesn't
> //do the datum shift.
> 
> So does this mean that the PostGIS transform() function won't do datum
> shifts? Can anyone with a bit more PROJ4 knowledge say if this is correct,
> and if so, why PostGIS can't support it?

I'm not responsible for that code, anyway with a closer look, that
function is only invoked as a second attempt if pj_transform()
returns -38. Line 930:

                if (pj_errno == -38)  //2nd chance

Finding meaning of -38 would be the next thing to do ...

--strk;