Creating a Canopy DEM from LiDAR

In a previous post, I described how to create a hybrid hillshade from a standard bare-earth DEM and a DEM including canopy.  Well, what if you don’t have a fancy canopy DEM? Do you have classified LiDAR data, or know where to get your hands on some? Then you are in luck! I’m here to walk you through the process of creating your very own canopy DEM in ArcGIS.

CanopyHeight.jpg

Your first step is to load your LiDAR data into an LAS dataset covering your area of interest. Next, you need to filter your LiDAR data to only get the elevations of features that you want, in this case the ground and the tree canopy, but not buildings. You can access the filter by opening the LAS dataset’s properties and navigating to the Filters tab. Select the categories Ground, High Vegetation, Medium Vegetation, and Road Surface. The categories you have available will depend on how finely your LiDAR data was classified. Apply your filter and close the Properties window.

filteredLAS_categories.jpg
Classified LAS dataset, symbolized by return type.

 

Now, you’ll run the LAS Dataset to Raster tool. To make this work correctly, you’ll need to select the “MAXIMUM” cell assignment type. If you were to use any of the other methods, the ground returns underneath the vegetation would lower your canopy values. Also, I think it’s best to specify your cell size using the CELLSIZE sampling type. A cell size of 3 ft (or 1 m, depending on projection) is about right for a canopy DEM, but adjust according to the LiDAR sampling rate and your needs. Once you have all your settings how you want them, run the tool.

CanopyDEM.jpg
Finished canopy DEM, symbolized by elevation, overlaid on composite hillshade.

 

And like that, you’re done! You can create a hillshade using the standard tools in Spatial Analyst or QGIS. For best results on making a composite hillshade, you should create your bare earth DEM from the same LiDAR dataset. Also, try your hand at a little raster math to create canopy height (canopyDEM – bareEarthDEM) and canopy cover (canopyHeight > x) rasters for your study area.

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Author: jcguarneri

Mapmaker, bicycle advocate, fisherman, naturalist. Follow me on Twitter @jayguarneri.

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