[Gdal-dev] srtm warping question

[Frank Warmerdam]

Michael Heins wrote:
> listers;
> 
> Continuation of my SRTM reprojection problem.
> 
> I convert SRTM - BIL format into GeoTiff using Gdal_translate:
> (so GeoTiff is in lat/long geographic coords)
> gdal_translate -ot CInt16 -a_nodata -32768 c:\srtmtest\N43W071.bil c:\srtmtest\outll.tif
> 
> Then I reproject lat/long GeoTif into a utm projection GeoTiff:
> gdalwarp -t_srs "+proj=utm +zone=11 +datum=WGS84" -ot CInt16 c:\srtmtest\outll.tif c:\srtmtest\oututm.tif
> 
> The resulting outll.tif is representative of the BIL in a grayscale representation.  This is as expected.
> HOWEVER, the resulting oututm.tif is all null; when viewed, it is all black.??  why?
> I have experimented with other sample tifs, and they seemed to be reprojected no problem.  This leads me to believe the Bil->Tif conversion is producing an errored Tif in some manner?
> 
> Can someone help me out with why this reprojection is not working?  does it have something todo with forcing the output type to 16bits?  And how can I go about to fix this?

Mike,

Why did you pick the data type CInt16 as opposed to Int16?  CInt16 is
"complex int 16", and involves a real and imaginary component.  I suspect
that the warper is not supporting complex data properly and that is why
you aren't getting a result.

Best regards,
-- 
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