[gdal-dev] Unexpected results with GDALDEM

[William Hudspeth, Ph.D.]

Hello all,

I am using gdaldem that came with the GDAL 1.7.3 version on Ubuntu 
12.04. I am trying to create slope maps with a command something like this:

gdaldem slope -s scale=111120 source_DEM.tif target_SLOPE.tif

the source DEM geotiff was created with gdalwarp, re-projecting a 
National Elevation Dataset 30 meter, ESRIHdr formatted grid from 
geographic-NAD83 to geographic-WGS84. Based on a thread I found on use 
of 'gdaldem slope' on the web, the re-projection was attempted with both 
a bilinear and cubic re-sampling method.

The target geotiff has values of only 90 and Null. I am getting no 
intermediate values (in degrees, the default).

Thanks for any help in advance,

Bill