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Map Algebra

Question asked by faithgreycloud on Jun 8, 2018

Hello my friendly GeoNet community!  I need to create a Canopy Height Model. I have a "DSM" that includes man-made structures. and a DEM. I digitized the structures, turned them into a raster and used a Con in Raster Calculator to create a raster layer of just the DEM values, and then mosaiced the DSM into the structures raster layer. So, hypothetically I would has a DSM with no man-made structures. I then used Raster Calculator to Subtract the DEM from the DSM (DSM - DEM) to get a CHM. the result has a bunch of values from -23 to 0... the DSM and the DEM are both 3 ft resolution from the same lidar flight. Does anyone have any ideas what may have gone wrong, or what I can do to fix it? 


Thank you!!