[gdal-dev] Encoding EPSG:3857 (WebMercator) in GeoTIFF, and ArcGIS interoperability

[Even Rouault]

Hi Pepijn,

> 
> How does this relate to http://trac.osgeo.org/geotiff/wiki/RefiningGeoTIFF?
> <http://trac.osgeo.org/geotiff/wiki/RefiningGeoTIFF?>

Very much (although I'm foolishly attempting to reach interoperability with 
existing implementations)

> 
> Frank wrote there that
> 
> > accepted industry practice has been to accept newer EPSG PCS and GCS
> > codes even though they are not explicitly listed in the GeoTIFF
> > specification
> 
> It’s not clear to me from the GeoTIFF spec what the correct way to convert
> EPSG PCS codes to GeoTIFF PCS codes is, but it does seem to indicate that
> this is done somehow already.

The relevant section is :
http://www.remotesensing.org/geotiff/spec/geotiff6.html#6.3.3

6.3.3.1 Projected CS Type Codes

Ranges:
   [    1,   1000]  = Obsolete EPSG/POSC Projection System Codes
   [20000,  32760]  = EPSG Projection System codes
   32767            = user-defined
   [32768,  65535]  = Private User Implementations

But there's a big hole for ]1000,20000[, and 3857 is in it. And even if it was 
in the [2000,3276] range, it didn't exist at the time of the latest GeoTIFF 
spec. Frank's "accepted industry practice" is to just make Projected CS Type 
Code = EPSG PCS code.

> 
> OGC started a SWG to do this GeoTIFF spec refinement work. Might be
> worthwhile to ask that group for input, although looking at their mailing
> list, github repo and wiki pages there doesn’t seem to be much going on at
> the moment (or at least there’s no record of it).

Yes, I've contacted one of the members.

I can't see a geotiff list at https://lists.opengeospatial.org/mailman/listinfo 
. Is it a public one ?

Thanks,

Even

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