I just can't get my head around it... :(
I have a Mars DEM rasterdata set that is projected in polar
stereographic with this Wkt:
PROJCS["POLAR_STEREOGRAPHIC MARS",
GEOGCS["GCS_MARS",
DATUM["D_MARS",
SPHEROID["MARS",3396190,169.8944472236118]],
PRIMEM["Reference_Meridian",0],
UNIT["degree",0.0174532925199433]],
PROJECTION["Polar_Stereographic"],
PARAMETER["latitude_of_origin",-90],
PARAMETER["central_meridian",0],
PARAMETER["scale_factor",1],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0]]
and a worldfile (output of ds.GetGeoTransform()
(-707109.6954345703,
115.08946865797043,
0.0,
707109.6954345703,
0.0,
-115.08946865797043)
So, currently, to find the corrent sample/line coordinates to determine
what raster window to read, I need to know the projected coordinate in
meters and using this via gdal.ApplyGeoTransform() works fine, in both
directions.
But I would like to find my data by providing a pair of unprojected,
i.e. geographical coordinates. So something like
sample, line = gdal.ApplyGeoTransform(t, lat,lon)
So I understand that I need a transformation between
polar_stereographic and lat/long projection, but I am stumped at how I
get a new wordfile?
I guess I can just take the above Wkt and change projection to lat/long
and remove the parameter section, but what do I do with the affine
transformation parameters? Where do I have to put them into the proj4
system to achieve what I need? Somehow no examples I can find explain
this part (or I can't see the forest because of all the trees.)
Any help would be appreciated deeply!!
Best regards,
Michael
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