[postgis-devel] Re: [postgis-users] 3D Datum shifts from postgis
strk at refractions.net
strk at refractions.net
Tue Oct 24 06:42:52 PDT 2006
I've committed a patch sending Z values to pj_transform().
When input is 2d only Z are sent as 0.0.
We need some test cases to check if it's really working.
--strk;
On Mon, Oct 23, 2006 at 03:40:58PM -0400, Frank Warmerdam wrote:
> Paul Ramsey wrote:
> >Well, I am pretty sure PostGIS only does transform() in 2d, no matter
> >what. But I also suspect that Proj4 only has a 2d internal model, which
> >means at the library level nothing may be available either.
> >
> >Frank, can you confirm what proj4 provides in terms of 3d shifts?
>
> Paul,
>
> The PROJ.4 pj_transform() function attempts to transform "z" as well
> as x and y. Note that datum shifts performed with grid shift files
> normally have no z shift. But 3/7 parameter transformations also affect
> Z, and if the shift is done strictly ellipsoid to ellipsoid then Z shifts
> are also possible.
>
> I think it would be desirable to connect up this Z shifting in
> pj_transform()
> to the Z coordinate of postgis geometries.
>
> Best regards,
More information about the postgis-devel
mailing list