[PROJ] Vertical Transformations?

[Paul Ramsey]

On Wed, Feb 20, 2019 at 3:58 AM Even Rouault <even.rouault at spatialys.com> wrote:

> With the vertconc.gtx grid available, you'll get
>
> $ echo "45 -100 100" | cs2cs -f "%.8f" EPSG:7406 EPSG:5500
> 44.99998071     -100.00039555 30.85853056
>
> Without it, you'll get just us-ft to metre for the vertical part:
> 44.99998071     -100.00039555 30.48006096

So, this is interesting... when running at the command-line, I get
your "no grid" result...

echo "45 -100 100" | cs2cs -f "%.8f" EPSG:7406 EPSG:5500
44.99998071 -100.00039555 30.48006096

When running the same thing in PostGIS, I get an error code back...

select st_astext(st_transform('SRID=7406;POINT(-80 40 100)'::geometry, 5500));
NOTICE:  PostGIS was unable to transform the point because either no
grid shift files were found, or the point does not lie within the
range for which the grid shift is defined. Refer to the ST_Transform()
section of the PostGIS manual for details on how to configure PostGIS
to alter this behaviour.
ERROR:  transform: couldn't project point (-80 40 100): failed to load
datum shift file (-38)

Specifically, error -38.
I guess now we get into angels-on-head-of-pin territory, but are there
proj error conditions that are best ignored? Raise a NOTICE? Something
else?

Also, I just installed version 1.8 of the proj grids project, is it
expected that I still not have the vertical grids in place for
NGVD29/NAVD88 conversion?

Thanks!
P