[postgis-users] ST_Transform Z heights between ODN and WSG [solved]

[Paul Ramsey]

Put a whole write-up here
http://blog.cleverelephant.ca/2023/02/proj-network.html

On Thu, Feb 2, 2023 at 8:00 AM Paul Ramsey <pramsey at cleverelephant.ca> wrote:
>
>
>
> > On Feb 2, 2023, at 1:58 AM, James Howe <jmh205 at cam.ac.uk> wrote:
> >
> > Thanks for the help to look in the right direction.
> > I downloaded the missing data files and it works now.
> >
> > # projsync --system-directory --source-id uk_os
> >
> > postgres=# SELECT st_asewkt(ST_Transform('SRID=7405;POINT(545068 258591 8.51)'::geometry, 4979));
> >                                st_asewkt
> > -------------------------------------------------------------------------
> > SRID=4979;POINT(0.121584703519227 52.20646902224667 54.461915505876696)
> > (1 row)
> >
> > I guess 3.0 reduced what was included by default?
>
> No, this is very much a proj and packaging thing. We just call the API.
> As modern proj got better at grid shifts and finding the best transform chains, the proj team started collecting more grids. Eventually the grid collection got so large that distributing it as one unitary package stopped seeming reasonable. So network/cdn access was adopted, but as a result a "bare" distribution now includes zero grids, whereas before it was common for a packaged proj to at least include grids for the "more common" transforms.
>
> P.
>
>
> >
> > James
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>