Hi,
depending on the parameters you defined in spatial_ref_sys, PostGIS
decides how to process the transformation, see
https://blog.cleverelephant.ca/2019/02/proj4-postgis.html
Try to define proj4text only:
insert into public.spatial_ref_sys (srid,proj4text)
select 93004,proj4text from spatial_ref_sys where srid =3004;
update spatial_ref_sys set proj4text ='+proj=tmerc +lat_0=0 +lon_0=15 +k=0.9996 +x_0=2520000 +y_0=0
+ellps=intl +nadgrids= +units=m +no_defs' where srid =93004; Florian
Am 16.12.2021 um 10:57 schrieb andy:
Hi,
I have a NTV2 file, and it works properly if I hardcode the parameters
in the query:
SELECT ST_AsText(
ST_Transform(
ST_GeomFromText('POINT(13.335462 41.132282)',4326),3004
)
) AS not_corrected,
ST_AsText(
ST_Transform(
ST_GeomFromText('POINT(13.335462 41.132282)',4326),
'+proj=tmerc +lat_0=0 +lon_0=15 +k=0.9996 +x_0=2520000
+y_0=0 +ellps=intl
+nadgrids=40441123_43581445_R40_F00.gsb +units=m +no_defs'
)
) AS corrected;
The output is:
- POINT(2380292.276247742 4554785.392090227)
- POINT(2380294.3337390865 4554784.22045453)
If I insert it in PostGIS
-- create new record
insert into public.spatial_ref_sys (srid, auth_name, auth_srid,
srtext, proj4text) select 93004 , auth_name, auth_srid, srtext,
proj4text from spatial_ref_sys where srid = 3004;
-- update it
update spatial_ref_sys set proj4text = '+proj=tmerc +lat_0=0 +lon_0=15
+k=0.9996 +x_0=2520000 +y_0=0 +ellps=intl
+nadgrids=40441123_43581445_R40_F00.gsb +units=m +no_defs' where srid
= 93004
and then I run
SELECT ST_AsText(
ST_Transform(
ST_GeomFromText('POINT(13.335462 41.132282)',4326),3004
)
) AS not_corrected,
ST_AsText(
ST_Transform(
ST_GeomFromText('POINT(13.335462 41.132282)',4326),93004
)
) AS corrected;
I obtain two equal results, as if it did not apply what was read in
the proj string in spatial_ref_sys:
- POINT(2380292.276247742 4554785.392090227)
- POINT(2380292.276247742 4554785.392090227)
I'm using PostgreSQL 13.5, compiled by Visual C++ build 1914,
64-bit, 3.1 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
I can't figure out what the problem could be. Why does it work
hardcoded and not via spatial_ref_sys?
Thank you
--
___________________
Andrea Borruso
website: https://medium.com/tantotanto
38° 7' 48" N, 13° 21' 9" E, EPSG:4326
___________________
"cercare e saper riconoscere chi e cosa,
in mezzo all’inferno, non è inferno,
e farlo durare, e dargli spazio"
Italo Calvino
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