Hi,
The -cc parameter is only taken into account if there's a CRS associated
to the DEM, as the sphere diameter isn't hardcoded to be the one of Earth.
So you should first check that there's a lunar one associated to yours
If you use PROJ >= 8.1, you can use IAU:30100 or otherwise the PROJ4
style string "+proj=longlat +R=1737400 +no_defs +type=crs"
Or you can create a VRT wrapping your DEM with something like:
gdal_translate your_input_dem temp.vrt -a_srs "+proj=longlat +R=1737400
+no_defs +type=crs"
and then use temp.vrt as input for gdal_viewshed and use -cc 1 as
there's no atmosphere on Moon (just thinking that gdal_viewshed should
probably default to -cc 1 for non-Earth bodies)
Even
Le 30/08/2022 à 01:45, Bradner, Kevin M. (ARC-TI) via gdal-dev a écrit :
Hello,
I'm interested in using gdal_viewshed
<https://gdal.org/programs/gdal_viewshed.html#gdal-viewshed> to
calculate a viewshed for a point on the surface of the Moon. My DEM
stores heights relative to a reference sphere approximately the size
of the Moon.
Could I calculate a valid viewshed from this data by passing in a -cc
of roughly 3.6 (Earth diameter / Moon diameter)? Some comments in the
algorithm's source code make this seem reasonable, but I would like to
confirm that this is the only correction I would need to make.
Thank you,
Kevin Bradner
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