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I am late on reporting these useful tidbits and for that I apologize. I learned of these techniques from Ian Madin from DOGAMI while I was at the AASG meeting in Park City way back in June. Ian is my LiDAR hero for the time being. Basically, he showed me some simple tricks that make complete sense in hindsight but struck me as nothing short of revolutionary when I applied them to my data set. Before I get into it, I will say again that LiDAR changes everything. It is a truly revolutionary tool for geologic mapping of any kind, but particularly for surficial geologic mapping.

OK. So you have your LiDAR and you love the super neato hillshade images that it can be used to generate. But, hey, what about those damn shadows in areas of key interest? Well, you can apply a redundant brute force approach to making hillshade images with different solar geometries…but that would be downright nutty. You could crank it up a methodological notch and use GlobalMapper or Surfer to create these images far more quickly and choose your favorite to export…but that would be silly as well (but kind of fun…except for the exporting part).
Step back and think about what you are trying to visualize with the hillshade….wait for it….slopes, right?!. So, what you do is effectively create a universal \ isotropic (?) hillshade image by using the ‘slope’ tool in the ArcGIS toolbox (3D analyst\ raster surface\ slope). Trust me, it works. However, you can’t just go with the default settings. You have to stretch the resulting data (std dev works best for me), invert the grayscale ramp (important) and sit back and take it all in. Sweet! But wait, you need to overlay a slightly tranparensized color ramp of the elevation data (stretched as well for simplicity) to make it tasty. Now you have it all. For some real fun, change the n value in the standard deviation stretch and see what happens (maybe stay between 1 and 3).
Click through the photoset for some comparisons and you just may become a believer. Obviously, having all of these visualizations at your immediate disposal is the way to go…the beauty of GIS for geology, no?
Maybe you noticed that the last one has a comfortably smooth contour overlay…how the hell did that get there? Stay tuned for a tip that even took an ESRI LiDAR braniac by surprise at the Users Conference.

Posted via email from Fresh Geologic Froth

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