[gdal-dev] gdaldem aspect is grid-oriented

Even Rouault even.rouault at spatialys.com
Fri Jun 25 03:26:14 PDT 2021


A general solution would have more appeal, although I suspect it will be 
a bit more computation intensive as you'll probably have to transform to 
invoke PROJ multiple times per grid point to compute the direction to 
the North


Le 25/06/2021 à 06:29, Michael Sumner a écrit :
> Hello, we're using `gdaldem aspect` on polar grid products and we need 
> to convert the grid-oriented directions to compass oriented ones, 
> location-specific directions, where "compass north" is dependent on 
> longitude.
> It's easy but inefficient for us to do this after running gdal dem for 
> our polar grids at latitude -90, and a more general solution would 
> require a general approach to "where north is" for any location in a 
> projection.
> I'll be able to modify GDAL to do this as an option to gdaldem for a 
> simple polar grid (e.g. EPSG:3031), and that will make our use of it 
> much more efficient. Is there any interest in a more general approach?
> Best, Mike
> -- 
> Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> Hobart, Australia
> e-mail: mdsumner at gmail.com <mailto:mdsumner at gmail.com>
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> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
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My software is free, but my time generally not.

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