[gdal-dev] Support for QSC in GDAL (was: Warp API / gdalwarp: using projection supported by PROJ4, but not explicitly by GDAL?)

Jed O. Kaplan jed.kaplan at unil.ch
Mon Nov 10 09:37:53 PST 2014

Dear GDAL developers,

I would like to resurrect this thread from a couple of years ago regarding GDAL support for the Quadrilateralized Spherical Cube (QSC) projection in GDAL.

Now that the QSC projection is supported by proj4 and works well, would it be possible to have the projection fully supported in GDAL, i.e., identifiable in a WKT string?

The QSC projection has many potential uses whenever working with global data and would be a valuable additional feature for GDAL.

Thanks in advance for your help!

Best regards,

Jed Kaplan

On Fri, 13 Jul 2012 12:01:21 +0200, Even Rouault wrote: 
> > I could certainly do that, but with the '+wktext' mechanism, there 
> > is no reason to add this patch anymore, is there? 
> Your patch is a cleaner solution than the +wktext mechanism, which 
> remains something a bit hacky (although I must admit I had never 
> heard before of that QSC projection ! and it is probably some niche 
> projection). The advantage of having it properly recognized is that 
> you can then embed its WKT representation in a .aux.xml file and all 
> tools using GDAL will be able to deal properly with it. 

Yes, QSC is very limited in scope and absolutely not widely used. It is 
a perfect fit for my use case (planetary-scale terrain rendering using 
quadtree hierarchies for data management), but I'm not sure it is worth 
adding general support for it to GDAL. For me, the '+wktext' solution 
already works fine since the transformation of data to the quadtree 
hierarchies is typically one way only: the resulting files are only 
ever used by the renderer. 

> But reading again your initial email, I didn't realize that it is not 
> yet supported in proj, only proposed. So we will wait for it to be 
> committed in PROJ first before committing its support in GDAL. 

OK, if QSC is accepted into PROJ and full support for it in GDAL is 
considered worthwhile, I can update the patch and create a ticket. 

Best regards 

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