Hi David, Can you clip out a small section of your DEM that contains both ocean and land and send it to me? Your question sounds interesting, and I'd like to take a look at the data before I comment on it.
Thanks, Roger -- On Wed, Apr 7, 2010 at 9:08 PM, David <dbainbri...@gmail.com> wrote: > Hello. I am having a terrible time trying to figure out how to convert > what should be value/height of 0 in the SRTM/hgt data file to the alpha > layer in a tiff. I was experimenting with making ocean areas transparent. > I tried the following with no success: > > gdalwarp -of GTiff -co "TILED=YES" -dstalpha -srcnodata 0 -wt Float32 -ot > Float32 -wo SAMPLE_STEPS=100 -multi N40W125.hgt test.tiff > > gdalinfo -mm gives: > Band 1 Block=256x256 Type=Float32, ColorInterp=Gray > Computed Min/Max=-32768.000,1233.000 > Band 2 Block=256x256 Type=Float32, ColorInterp=Alpha > Computed Min/Max=0.000,255.000 > > Since this may affect the hillshading for any land areas inland I was also > going to attempt the same affect by masking the ocean after the hillshading. > > The resulting tiff in either case would be overlaid onto another layer that > would have any land areas filled in with the resulting color that would have > been used with height 0 in the hgt file. I am doing this because I have a > coastline shapefile that represents land areas but not ocean areas. > > Is my approach a good idea and/or what am I missing to mask the ocean areas > into the alpha layer? > Thanks for any help. > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev >
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