Opened 6 years ago

Last modified 2 years ago

#4127 new enhancement

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

Reported by: armin Owned by: warmerdam
Priority: normal Milestone:
Component: GDAL_Raster Version: unspecified
Severity: normal Keywords: ECW, CRS
Cc: dgrichard


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

Attachments (2)

ecw_cs_eu.wkt (62.7 KB) - added by armin 6 years ago.
ecw_cs.wkt.patch (46.9 KB) - added by armin 6 years ago.

Download all attachments as: .zip

Change History (9)

Changed 6 years ago by armin

Attachment: ecw_cs_eu.wkt added

comment:1 Changed 6 years ago by yjacolin


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?



comment:2 Changed 6 years ago by warmerdam

Cc: dgrichard added

comment:3 Changed 6 years ago by 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"]]

comment:4 Changed 6 years ago by 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.

Changed 6 years ago by armin

Attachment: ecw_cs.wkt.patch added

comment:5 Changed 6 years ago by 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.

comment:6 Changed 2 years ago by Jukka Rahkonen

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

comment:7 Changed 2 years ago by Jukka Rahkonen

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