csny490

Detect areas of "crystal/pyrite forest" in LiDAR DTM

Discussion created by csny490 on Sep 12, 2013
Latest reply on Sep 18, 2013 by csny490
Looking for some creative ideas...

Here in Western WA State, we have a lot of dense forest/brush. Often the LiDAR laser has a hard time getting good ground returns in dense shrubberies - which results in a funny looking "crystal forest" shapes in the DTMs, where the facets of the ground surface TIN are readily visible due to low mass ground point densities. Here's a picture:[ATTACH=CONFIG]27414[/ATTACH].

I am trying to come up with a reasonably good/fast method of locating "crystal forest" areas like this, given ONLY the bare earth DEM (not the original LAS/ascii raw point files). The best method I have come up with is to create an aspect raster, and do a 3-5 cell radius focal variety - thus counting the "diversity" of aspect angles in a relatively small analysis window. The idea being that areas of low aspect variety (and a slope >= 5% of so) are indicative of these rather planar TIN facet shapes. One issue is that there are also areas of quite planar hill slopes where the aspect is also very similar (think a large planar hill slope facing north). So, while the aspect focal variety method does a pretty good job finding the crystal forest areas, it also is pretty good at finding the planar hillslopes as well. I already have a mask screeing out flat areas such as lakes/ag field/etc.  so that's been taken care of.

Super bonus points if you have any good ideas!

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