[GRASS-user] wierd artifacts in DEM from seamless.usgs.gov

[Dylan Beaudette]

Howdy,

downloaded a 1/3 arc-second (about 10m res) DEM from the seamless.usgs.gov 
site. 

projected the lat/lon raster to UTM via gdalwarp using the -tps option

import into grass, and compute shaded relief... and it looks like crap:
http://169.237.35.250/~dylan/temp/seamless_dem_artifacts.png

so far the only way that i have been able to get a somewhat decent DEM from 
this file is to :

a) average the heck out of it via r.neighbors size=15 or so
b) smooth it with r.param.scale size=15 or so

the artifacts appear to be at a regular interval ... 

any thoughts one what could be causing this? I have never had this happen 
before, although I have seen numerous scan-line style errors like this in 
USGS DEM products. thoughts of artifact removal bring to mind the recently 
mentioned Albani and Klinkeberg paper [1] and another by Oimoen [2] .

Any thoughts on how to proceed? perhaps a combination of band filters applied 
in the direction and orthagonal to that of the artifacts?

1.http://scholar.google.com/url?sa=U&q=http://www.geog.ubc.ca/courses/geog516/notes/Albani_and_Klinkenberg_ASPRS2003.pdf

2.http://scholar.google.com/url?sa=U&q=http://edna.usgs.gov/Edna/pubs/artifacts.pdf


I was hoping to use this area in the upcoming Where 2.0 talk, and it is 
looking like I might have to choose an area with better elevation data if 
this cannot be resolved. If it can be, then it would be a great slide to add!

Cheers,

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341