With further experimentation it seems that 32767 does seem to be the
correct value for the -srcnodata option. I've also found that if I
omit the -dstnodata option from the gdalwarp command the black holes
do not appear, presumably because the void data is then not included
in the reprojected image.
Cheers
Adam
On 1/10/2009, at 3:56 PM, Adam Ratcliffe wrote:
I've created a hillshade image using the NASA SRTM3 data following
the notes at: http://wiki.openstreetmap.org/wiki/HikingBikingMaps.
Looks great except for the occasional 'black hole' in the image, I
expect this is due to data voids not being rendered correctly.
What's got me puzzled about this is that the wiki page suggests
using a value of 32767 for the -srcnodata and -dstnodata options to
gdalwarp, howver in the NASA docs (http://dds.cr.usgs.gov/srtm/version2_1/Documentation/Quickstart.pdf
) it says data voids are assigned the value -32768.
Should I be using the NASA value for -srcnodata and -dstnodata
instead?
Cheers
Adam Ratcliffe
Software Developer
GeoSmart
PO Box 101001
29 Apollo Drive, Mairangi Bay, Auckland, NZ
Ph: +64 9 9668757 Fx: +64 9 966 8721
Email: [email protected]
Web: www.GeoSmart.co.nz
SmartNAV - The premier Car Navigation dataset for NZ
SmartFIND - Web and Mobile mapping solutions by GeoSmart
www.aamaps.co.nz - For FREE web maps and directions within NZ
Route2GO - Optimised journey planning to create the most efficient
routes to your customers for your sales or service calls
<ATT00001.txt>
Adam Ratcliffe
Software Developer
GeoSmart
PO Box 101001
29 Apollo Drive, Mairangi Bay, Auckland, NZ
Ph: +64 9 9668757 Fx: +64 9 966 8721
Email: [email protected]
Web: www.GeoSmart.co.nz
SmartNAV - The premier Car Navigation dataset for NZ
SmartFIND - Web and Mobile mapping solutions by GeoSmart
www.aamaps.co.nz - For FREE web maps and directions within NZ
Route2GO - Optimised journey planning to create the most efficient
routes to your customers for your sales or service calls
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