John Stevenson schrieb:
Hi,
I have imported some tiles of 1 arcsecond SRTM data into GRASS 6.3 using
r.in.srtm into a lat-long region. Whenever I import them to a UTM
region, res=30, I get aliasing problems. This results in a grid of
lines of jumps in elevation running through my data.
This happens when I use r.proj. I have also tried generating a text
file of UTM coordinates via r.stats -1g, and cs2cs. Importing this as a
raster or vector, and interpolating with r.surf.rst or v.surf.rst also
give aliasing errors.
What is the best way round this? Importing at a higher resolution? How
much higher? My ultimate aim is to compare the SRTM with LiDAR data, so
if possible I would like to use an exact interpolation where possible.
Cheers
John
You have to check what interpolation methods are used. If you don't
specify anything, Grass might use "nearest", but I'm only using Grass
rarely.
For myself I use gdalwarp with cubic or cubic spline resampling for that
task.
http://gdal.org/gdalwarp.html
Regards
Wolfgang
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user