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

[Dmitry Baryshnikov]

Sorry for some spam in GeoTIFF topic.

I'll create some shape files and screenshots and attach them to the 
ticket #3962 to explain what  I mean.

Best regards,
     Dmitry

16.04.2015 00:10, Even Rouault пишет:
>> The ArcGIS (or QGIS in qpj) save 3857 in such prj file:
>>
> I hoped that this thread could remain focused just about GeoTIFF encoding.
> Shapefile encoding issues are a different matter (see
> http://trac.osgeo.org/gdal/ticket/3962)
>
>> PROJCS["WGS 84 / Pseudo-Mercator",
>>       GEOGCS["WGS 84",
>>           DATUM["WGS_1984",
>>               SPHEROID["WGS 84",6378137,298.257223563,
>>                   AUTHORITY["EPSG","7030"]],
>>               AUTHORITY["EPSG","6326"]],
>>           PRIMEM["Greenwich",0,
>>               AUTHORITY["EPSG","8901"]],
>>           UNIT["degree",0.0174532925199433,
>>               AUTHORITY["EPSG","9122"]],
>>           AUTHORITY["EPSG","4326"]],
>>       PROJECTION["Mercator_1SP"],
>>       PARAMETER["central_meridian",0],
>>       PARAMETER["scale_factor",1],
>>       PARAMETER["false_easting",0],
>>       PARAMETER["false_northing",0],
>>       UNIT["metre",1,
>>           AUTHORITY["EPSG","9001"]],
>>       AXIS["X",EAST],
>>       AXIS["Y",NORTH],
>>       EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0
>> +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext
>> +no_defs"],
>>       AUTHORITY["EPSG","3857"]]
>>
> Are you 100% positive that ArcGIS generates such a .prj ? This doesn't look
> like classical ESRI WKT (which generally lacks most AUTHORITY nodes and has no
> EXTENSION PROJ4 stuff), but like GDAL WKT.
>
>> And GDAL opens such shape file and set the spheroid.
>> But if I save the shape file in 3857 via GDAL I get ellipsoid:
>>
>>     PROJCS["WGS_84_Pseudo_Mercator",
>>       GEOGCS["GCS_WGS_1984",
>>           DATUM["D_WGS_1984",
>>               SPHEROID["WGS_1984",6378137,298.257223563]],
>>           PRIMEM["Greenwich",0],
>>           UNIT["Degree",0.017453292519943295]],
>>           PROJECTION["Mercator"],
>>           PARAMETER["central_meridian",0],
>>           PARAMETER["false_easting",0],
>>           PARAMETER["false_northing",0],
>>           UNIT["Meter",1],
>>           PARAMETER["standard_parallel_1",0.0]]
> Yes, that's the result after morphToESRI(). Which is probably not the right
> ESRI WKT for WebMercator, anyway... Should rather be something like the
> following according to http://trac.osgeo.org/gdal/ticket/3962 :
> PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
>      GEOGCS["GCS_WGS_1984",
>          DATUM["D_WGS_1984",
>              SPHEROID["WGS_1984",6378137.0,298.257223563]],
>          PRIMEM["Greenwich",0.0],
>          UNIT["Degree",0.0174532925199433]],
>      PROJECTION["Mercator_Auxiliary_Sphere"],
>      PARAMETER["False_Easting",0.0],
>      PARAMETER["False_Northing",0.0],
>      PARAMETER["Central_Meridian",0.0],
>      PARAMETER["Standard_Parallel_1",0.0],
>      PARAMETER["Auxiliary_Sphere_Type",0.0],
>      UNIT["Meter",1.0],
>      AUTHORITY["ESRI","102100"]]
>
>> And both GDAL(QGIS) and ArcGIS open this shape file and set the ellipsoid!
> I don't understand what you mean here.
>