[gdal-dev] Weird results with gdaldem slope

George grub80 at gmail.com
Mon Feb 11 22:17:51 PST 2013


Hi there,

I am using gdaldem to get a slope raster from a DEM (source: ASTER), but it
seems like I can't get a correct result. For comparison purposes I did the
same steps using Arcgis 10.0. In particular, I followed two procedures:

Procedure 1
1. Mosaiced different DEM rasters together
2. Projected the mosaic coordinates to linear
3. Calculated slope (for gdal: gdaldem slope with no extra options)

The result I get is ok, but there are some linear features that are clearly
artificial. ArcGIS  gave the same result.

Procedure 2
1. Mosaiced different DEM rasters together
2. Calculated slope (for gdal: gdaldem slope -s 111120)
3. Projected the slope raster in linear coord.

The result is perfect in ArcGIS, while gdaldem returns a rsater that looks
all white with some black dots (in greyscale, using the same scale of the
ArcGIS one).

What am I doing wrong? I am new to the mailing list (and gdal), so I am not
sure if it's ok to attach examples. If you need them, I'll be happy to post
the rasters.


George
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