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OSGeo / PROJ-data

Repository for proj datum grids (for use by PROJ 7 or later)
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Add geoid grid fr_ign_RAF20.tif #83

Closed p-assali closed 2 years ago

p-assali commented 2 years ago

Add the up to date geoid grid for mainland France RAF20.

For mainland France, the RAF20 geoid grid was updated at the end of 2021 to take into account the maintenance operations of the RGF93 geodetic system.

Following grid tools have been used to produce and check the Geodetic TIFF grid (GTG) file :

rouault commented 2 years ago

See https://github.com/OSGeo/PROJ-data/blob/master/CONTRIBUTING.md for the other files to update (the version to indicate in the version_added column of copyright_and_licenses.csv will be 1.10) Looking at the metadata of the GeoTIFF file, it should be amended. The geographic CRS to use should be EPSG:9781 for the 3D geographic CRS "RGF93 v2b" . See https://epsg.org/transformation_9876/RGF93-v2b-to-NGF-IGN69-height-5.html A corresponding pull request to the https://github.com/OSGeo/PROJ repository would be appreciated to register the new grid (as indicated in the above mentioned CONTRIBUTING.md)

rouault commented 2 years ago

@p-assali quick remainder that this pull request needs follow-up to be integrated. update w.r.t my previous comment: the version number will be 1.11 since 1.10 is about to be released

p-assali commented 2 years ago

@rouault Thanks for the reminder and all the previous indications that I had not considered. My bad ! Everything should be fine now, since GeoTiff metadata has been updated with the dedicated EPSG:9781, and all other files edited as requested (with version number 1.11). Regarding the request of a corresponding PR to https://github.com/OSGeo/PROJ repository, I'm not sure if this is necessary, or how this should be done. The transformation between source and target CRS is already referenced in the PROJ database (file grid_transformation.sql).

INSERT INTO "grid_transformation" VALUES('EPSG','9876','RGF93 v2b to NGF-IGN69 height (5)','Replaces RAF18b geoid model [RGF93 v2 to NGF-IGN69 height (4)]. Accuracy at each grid node is in the geoid model file. Recommended interpolation method is bilinear. For reversible alternative see RGF93 v2b to RGF93 v2b + NGF-IGN69 height (5) (code 9877).','EPSG','1073','Geographic3D to GravityRelatedHeight (IGN2009)','EPSG','9781','EPSG','5720',0.01,'EPSG','8666','Geoid (height correction) model file','RAF20.tac',NULL,NULL,NULL,NULL,NULL,NULL,'IGN Fra 20',0);

Please let me know if I still need to do something on that point.

rouault commented 2 years ago

could you please drop the changes in files.geojson ? There are encoding issues and other suspicious changes. I'll regenerate that file on my side, once your PR is merged.

yes, a pull request to OSGeo/PROJ is needed so that the 'RAF20.tac' name in the EPSG dataset is bound to the fr_ign_RAF20.tif file. See https://github.com/OSGeo/PROJ/commit/098a661d7e57df71fddf064a55318df9cee4a280 for a very similar use case. To check that it works properly, "projinfo -s EPSG:9781 -t EPSG:5720 -o PROJ" should display a PROJ string with the .tif filename in it.

p-assali commented 2 years ago