Module 2: Shenandoah National Park-DEM/DSM, Tree Height and Tree Density LIDAR Analysis

LiDAR, or light detection and ranging, data is a very useful tool for foresters to understand the forest canopy and terrain, which is useful information for monitoring forest health, calculating forest biomass, classifying terrain, identifying watersheds, etc. In this lab, ArcGIS Pro was used to analyze USGS Lidar data in the form of a .las file to create a digital elevation model, which shows bare earth elevations, and a digital surface model, which shows both natural and man-made features, like buildings and trees. The LAS DATASET TO RASTER tool was used to create both the DEM and DSM. However, the DEM appearance was set to filter for Ground points before using the tool, while the DSM appearance was set to filter for Non Ground points. The Minus tool can calculate the difference in height from the ground and the tree canopy surface, or essentially the tree height. The negative values are located along roads or clearings. This likely means there was some return issue along the forest edges, but the number of negative values wasn’t large enough to have an impact on the analysis results. The below map shows the resulting tree height raster and tree height distribution chart. Lower tree heights, or areas with no trees, are purple and the tallest trees are red.

To calculate the tree density, several tools were used, including LAS TO MULTIPOINT, POINT TO RASTER, IS NULL, CON, PLUS, FLOAT, and DIVIDE. The final tree density raster is shown below, in which the lowest density is red and the highest tree density is blue: 

This map shows a man-made road toward the southeast corner and tree clearings in the southwest corner. 

Finally, a 3D scene of the DSM was created. The HILLSHADE tool, under Raster Functions, was used to create a shaded hillshade layer that is placed beneath the DSM layer. The DSM layer color symbology is updated to a green to red color ramp and is made transparent so the hillshade layer comes through to create a 3D appearance. Then, the map is converted into a local 3D scene, found under the View tab, and positioned using the control rings. The final map is below with a tilted angle and shows the higher elevations as red and lower elevations as green:

I think these maps are the most interesting maps I have created so far. This module also introduced creating DEM and DSM data, which has many applications. Also, it provided the opportunity to work in a local 3D scene and see the data in different angles, which was very cool to see!