[PATCH] Additional CRS definitions for ECW file ecw_cs.wkt

[armin]

I have put together some additional definitions for various national European and pan-European projections, including datum definitions.

[yjacolin]

Hello,

I see in your file this line (l. 88):

RGF93,GEOGCS["RGF93",DATUM["Reseau_Geodesique_Francais_1993",SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6171"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4171"]]

But RGF83 already exists, a little bit different:

RGF93,GEOGCS["FRANCE 1993",DATUM["RGF93",SPHEROID["GRS80",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]]

What this modification improve projection?

Regards,

Y.

[dgrichard]

the data/ecw_cs.wkt of the trunk, one can be find another (third) RGF93 definition !

The addition seems to be correct, except for the AXIS definition part where IGN (the French NMA in charge of maintaining the CRS) uses the longitude, latitude order explicitly.

I would then suggest to keep the AXIS order explicit in the WKT definition.

Another point to agree upon is related with the AUTHORITY clause : currently, data/ecw_cs.wkt uses IGNF for this system, whilst the new definition uses EPSG. As the AUTHORITY clause allows an external authority to manage the definition of an entity, I would prefer keeping IGNF.

Therefore, I am more in favor of keeping the current record in the data/ecw_cs.wkt file with the appropriate changes on AUTHORITY for geogcs and datum clauses :

RGF93,GEOGCS["RESEAU GEODESIQUE FRANCAIS 1993",DATUM["RESEAU GEODESIQUE FRANCAIS 1993",SPHEROID["IAG GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0.0000,0.0000,0.0000,0,0,0,0],AUTHORITY["IGNF","REG024"]],PRIMEM["Greenwich",0.000000000,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AXIS["Longitude",EAST],AXIS["Latitude",NORTH],AUTHORITY["IGNF","RGF93G"]]

[armin]

I just have overlooked the other definitions for RGF93, otherwise I would not have added it a 3rd time...

I found now also a few other entries that seem to exist already, but are missing parameters like datum shift, like OSGB36 or TM65. So I think it would make more sense to modify the current file from trunk and add a DIFF file to this ticket. And I found a few more EU projections which I was missing in the current file, I will add them as well.

I am not sure about the naming conventions and what's best, I tried to base them on the ones from GDAL and EPSG and just putting them in a short form. Sometimes not really easy to give them names that somehow make sense, and I didn't know what is the maximum length.

[armin]

I uploaded a patch for the modified and newly added EU projection and datum definitions. Compared to my first file I removed also the datum parameters from the pure projection definition since this seems to be the standard way how it is done.

[Jukka Rahkonen]

This patch has not been applied yet into /trunk/gdal/data/ecw_cs.wkt

[Even Rouault]

This ticket has been automatically closed because Trac is no longer used for GDAL bug tracking, since the project has migrated to GitHub. If you believe this ticket is still valid, you may file it to ​https://github.com/OSGeo/gdal/issues if it is not already reported there.