I have a problem with my DEM again. I decided to use ASTER GDEM2 (for different reasons). ASTER GDEM2 have its problems, I know, and I dont want to discuss that again. I have to use it, because SRTM (USGS, CSI; Viewfinder) is not usable for my purpose.

So, there are 2 bad areas in my ASTER DEM: enter image description here

These areas a nearly okay in CSI so I could fill these errors of the ASTER GDEM2 with it. But I guess, the result wont be as good as I want to (the mountain in fact is 500m from ground! SRTM say 350m). I also have a topographic map, a very old one, but the contours seems to be more accurate then SRTM and ASTER.

How can I correct the ASTER GDEM with SRTM or analog contours from my map?


1 Answer 1


The interpolation modules in GRASS can work with a line vector, such as contour lines, to create a DEM raster. So you could create a DEM raster from your contour lines, then "correct" the ASTER GDEM with this data. The catch will be in matching elevations from the contour-based raster to the ASTER GDEM, to avoid a terrace effect at the edge. The procedure might be:

# Import the contour lines, 
# clipping to include only the area you want to correct, then:  
v.in.ogr dsn=contour.shp out=contour type=line spatial=xmin,ymin,xmax,ymax
# Set the region to match this new vector, 
# and choose resolution suitable for the size of the area
g.region -p vect=contour res=10
# Now interpolate contour-based dem
v.surf.rst in=contour elev=ctour_dem
# Import your ASTER tile and set region to that map
r.in.gdal in=aster.tif out=aster_dem
g.region -p rast=aster_dem
# Finally, patch the two rasters such that 
# pixels from the correct dem replace the aster_dem
# r.patch users the first raster in the list, 
# then fills in null cells from the second
r.patch in=ctour_dem,aster_dem out=correct_dem

That might help

  • 1
    You must be aware of the vertical differences of the two models, because of 3D different ellipsoids (but these differences do not go over 50 m). Commented Jan 31, 2013 at 12:05

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