Viewshed analysis problems

Discussion created by lekohut on Aug 19, 2011
Hey all,
I am having some trouble with my viewshed analysis and thought I would post here to see if anyone has any tips. I have run the analysis more times than I can count, tweaking the setting to try to get more accurate results, but can't get the results to even approximate the the actual visibility. What seems most peculiar to me is that the areas surrounding my viewshed points are often shown as nonvisible, despite the fact that looking at the DEM, I can't find any elevation rise that would cause that kind of result. My primary questions are:

1. DEM. I have been working with 30m ASTER DEM, one that is floating point and the other is the GDEM data in signed integer. I read that floating point is best, but the integer DEM I have is better quality. Should I avoid the integer DEM entirely, or is it usable, just not ideal?
2. When I projected the DEM I selected "bilinear" for the resampling technique. I read that either bilinear or cubic should be used for DEMs, but is one better for this type of analysis?
3. Aside from setting the OFFSETA, all other parameters should should default to maximal ranges correct (radius, viewing angle, azimuth)?

Any suggestions are much appreciated.