[gdal-dev] Patch for GDAL Web Mercator Issue / trac 3962

[Michael Rosen]

I considered the very same issue and opted for a pragmatic solution.  Here's my internal notes on this:

This approach seems consistent with what Frank W proposed<http://trac.osgeo.org/gdal/ticket/3962>:
"I am thinking that we should move to treating the pseudo-mercator projection method better in WKT, and tying the various systems together properly. Either use a custom projection like ESRI ("Mercator_Auxiliary_Sphere") or introduce the "Auxilary_Sphere_Type" parameter to standard Mercator.
I'll note that some of the names are different than what EPSG-registry.org has to say about all this<http://www.epsg-registry.org/report.htm?type=selection&entity=urn:ogc:def:crs:EPSG::3857&reportDetail=long&title=&reportDetail=long&style=urn:uuid:report-style:default-with-code&style_name=OGP%20Default%20With%20Code&title=>.

-          I'd like to see ESRI recognize a Projection Name of "Pseudo_Mercator" and for GDAL to use this string instead of "Mercator_Auxiliary_Sphere" since that's the alias used by EPSG. OTOH, if we leave it as Mercator_Auxiliary_Sphere, then our fix would work for older versions of ArcGIS...

-          That the parameters are "central_meridian" and "standard_parallel_1" instead of "Latitude/Longitude of Natural Origin" seems wrong but that happens a lot comparing other GDAL/EPSG transforms.  For example we have exactly this mismatch with the Mercator_1SP projection method used by WGS84 / World Mercator (3395).  I think it would be ill-advised to push to change this.


From: gdal-dev-bounces at lists.osgeo.org [mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Stefano Iacovella
Sent: Thursday, August 29, 2013 2:22 PM
To: Even Rouault
Cc: gdal-dev
Subject: Re: [gdal-dev] Patch for GDAL Web Mercator Issue / trac 3962


2013/8/29 Even Rouault <even.rouault at mines-paris.org<mailto:even.rouault at mines-paris.org>>
Well this is the name of the projected coordinate system. But here we are
talking more about the projection method (sorry for being pedantic...). The
EPSG registry would suggest "Popular Visualisation Pseudo-Mercator" for it.

On the contrary, thank you for letting me understand better and sorry for the noise :)
Kind Regards,
Stefano

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