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OSGeo / PROJ-data

Repository for proj datum grids (for use by PROJ 7 or later)
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Adding geoid file for vertical transformation at Svalbard #86

Closed himsve closed 2 years ago

himsve commented 2 years ago

Adding geoid file for vertical transformation at Svalbard, ETRS89 height (EPSG:4937) > SVD2006 height (EPSG:20000).

All crs'es, datums and tranformations are already registered in EPSG.

rouault commented 2 years ago

TYPE=VERTICAL_OFFSET_VERTICAL_TO_VERTICAL for the metadata in the GeoTIFF file isn't correct. It should be TYPE=VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL

himsve commented 2 years ago

The branch is probably prepared for reindexing @rouault.

rouault commented 2 years ago

@himsve can you try reverting the changes in files.geojson ? (UTF-8 encoding corruption). I'll regenerate on my side

rouault commented 2 years ago

All crs'es, datums and tranformations are already registered in EPSG.

@himsve will you follow up with a PR to PROJ to add the mapping from the EPSG grid name to the PROJ one ?

jjimenezshaw commented 2 years ago

Hi @himsve I'm now having a look at the GeoTIFF. Do you know why the file covers such a big area while the specs says "Arctic - 81°10'N to 76°10'N, 4°W to 38°E" ? gdalinfo on the geotiff says:

Corner Coordinates:
Upper Left  (-180.0000000,  90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"N)
Lower Left  (-180.0000000,  64.0000000) (180d 0' 0.00"W, 64d 0' 0.00"N)
Upper Right ( 180.0000000,  90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"N)
Lower Right ( 180.0000000,  64.0000000) (180d 0' 0.00"E, 64d 0' 0.00"N)
Center      (   0.0000000,  77.0000000) (  0d 0' 0.00"E, 77d 0' 0.00"N)

in ETRS89

himsve commented 2 years ago

That's correct, the file is bigger than the specified extent "Arctic - 81°10'N to 76°10'N, 4°W to 38°E" - EPSG:4058. The grid is based on results from the project "Arctic Gravity Project 2006". From that project a new geoid model of the north pole area was released. The geoid model was named arcgp-2006. Later on a modified version of arcgp-2006 was released to fit the Mean Sea Level at Svalbard.

Registration at EPSG: https://epsg.org/crs_20000/SVD2006-height.html?sessionkey=ui7a9oaoup: "Mean Sea Level (MSL) at Ny-Ålesund. The SVD2006 surface (arcgp-2006-sk) is the Arctic Gravity Project 2006 (arcgp-2006) surface adjusted to two benchmarks tied to the Ny-Ålesund tide gauge. arcgp-2006-sk=arcgp-2006 - 0.8986m."

arcgp-2006-sk has the same size as the original model arcgp-2006 . The completed arcgp-2006-sk model is registered at EPSG in Gravsoft bin-format with usage scope "Arctic - 81°10'N to 76°10'N, 4°W to 38°E", without any clipping of the model to fit the extent.