[PROJ] Wrong transformation in NL?

[Lesparre, Jochem]

Hi Even,

Amersfoort ellipsoidal heights were used in the past and could still be used under certain conditions. The transformation via 3D Amersfoort (your 1st example) taken here is needlessly complex (using the horizontal grid for the interpolation CRS of the geoid, but not for the horizontal coordinates), but it is correct within the accuracy. In the area of use, the maximum differences with the transformation via ETRS89-NLD [AGRS2010] recommended by the national authorities (your 2nd example) are 0.25 m horizontally and a few centimetres vertically.

Nevertheless, I'm still going to ask EPSG for changes that will favour or force transformation via ETRS89-NLD [AGRS2010] instead of 3D Amersfoort.

Regards, Jochem


1st example
$ echo 52 5 0 |  PROJ_NETWORK=ON bin/cs2cs -d 4 --3d EPSG:4326+3855 Amersfoort | PROJ_NETWORK=ON bin/cs2cs --3d -d 4 Amersfoort "Amersfoort + NAP height"
52.0010    5.0004 0.1953

2nd example
$ echo 52 5 0 |  PROJ_NETWORK=ON bin/cs2cs -d 4 EPSG:4326+3855 "Amersfoort + NAP height"
52.0010    5.0004 0.2000


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