[gdal-dev] Transformations with same horizontal datum but different geoid outputs the same Z value

[Even Rouault]

Diogo,

There are far more CRS definitions in the PROJ database, mostly coming 
from the EPSG dataset, than there are known transformations from/to 
those CRS to other ones
>
> Genoa 1942 height (Italy)
>
> $echo  "14.995 37.755 3357"  |  PROJ_NETWORK=ON gdaltransform --debug on -s_srs"EPSG:4326+3855"  -t_srs"EPSG:32632+5214"
> >>  1028333.73796622 4195591.29690422 3357
In that situation, "projinfo -t EPSG:32632+5214 -s EPSG:4326+3855 
--spatial-test intersects" shows a potential transformation, but that 
requires that you need to get (buy) the geo_igm_mar06.grd grid which 
does the "ETRS89 to Genoa 1942 height" transformation from 
https://www.igmi.org/en and convert it into a format understood by PROJ
>
> N2000 (Finland)
>
> $echo  "25.15296 62.50195 269"  |  PROJ_NETWORK=ON gdaltransform --debug on -s_srs"EPSG:4326+3855"  -t_srs"EPSG:3067+3900"
> >>  404861.868388335 6931460.32557422 269

There's no known transformation between N2000 and ETRS89 or WGS84 in the 
database.

That said 
https://www-maanmittauslaitos-fi.translate.goog/kartat-ja-paikkatieto/asiantuntevalle-kayttajalle/koordinaattimuunnokset/fin2005n00-geoidimalli?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp 
shows that there is a FIN2005N00 geoid model that exists for N2000 <--> 
ETRS89, so there's potential if that was registered in EPSG.

That said, if you use the online converted at 
https://kartta.paikkatietoikkuna.fi/?lang=en to do the N2000 <--> 
ETRS89, you can get the result:

1) Transform from EPSG:4326+3855 to ETRS89 3D

$ echo 25.15296 62.50195 269 | PROJ_NETWORK=ON gdaltransform -s_srs 
EPSG:4326+3855 -t_srs EPSG:4939
25.15296 62.50195 287.822128823693

2) Use the online transformer from EUREF-FIN-GRS80h (~= EPSG:4939) to 
EUREF-FIN-GRS80 + N2000

==> lat=62.50195 lon=25.15296 H=269.2867

3) Transform fromEUREF-FIN-GRS80 +  N2000 to EPSG:3067+3900

$ echo 25.15296 62.50195 269.2867  | PROJ_NETWORK=ON gdaltransform 
-s_srs EPSG:4258+3900 -t_srs EPSG:3067+3900
404861.868388335 6931460.32557422 269.2867


> EVRF2007 (Estonia)
>
> $echo  "27.059167 57.714444 318"  |  PROJ_NETWORK=ON gdaltransform --debug on -s_srs"EPSG:4326+3855"  -t_srs"EPSG:3301+5621"
> >>  682284.606829111 6401087.4159131 318

There's only one known transformation between EVRF2007 and ETRS89 or 
WGS84, but it is for Slovakia.

Even


-- 
http://www.spatialys.com
My software is free, but my time generally not.
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