GIS4048 M2, Digital Elevation Mapping
This was a frustrating lab, because I had trouble getting the initial LAS file to convert and render. It was provided in the module and we had instructions for getting it from the Virginia LiDAR site, but I had trouble with the first not loading and the latter not being accessible because of display setting issues on my computer. Once I got this figured out with help from UWF staff, I was able to do most of the lab in a short sitting.
I used the LAS Dataset to Raster tool twice, first filtering to ground points for the Digital Elevation Map, and then to non-ground for the DSM. Using the Minus tool to subtracting the DEM from the DSM gave me a height raster with values ranging from around -5 to 163. This was the basis for the tree height map, and the DEM was a separate map.
I created a histogram from the height raster to analyze vegetation height distribution. I used “value” in the histogram after some trial and error.
I ran the LAS to Multipoint tool twice, for ground and vegetation. I used the average point spacing from the Point File Info table. The Gorund Multipoint filled the area completely, while the Vegetation multipoint didn’t’ fully render. However, once converted to a raster all the data was there.
I converted both multipoint layers to rasters using Point to Raster with a cell size of 3. Then I used IS NULL and Con tools to prep the rasters for analysis, followed by Plus, then Float, then Divide to find canopy density. Getting the correct version of each tool (Spatial Analyst version) was confusing, because several of these tools are named the same but with different descriptions (spatial analyst, image analyst, 3-d analysis, etc.)
In the final layouts, I made 3 final maps showing tree height, canopy density, and a DEM. I included the histogram in the tree height map per instructions, but I couldn’t figure out inserting a chart, it wouldn’t populate in any insert menus. I was finally able to do it by copying the chart and pasting directly to the map, which didn’t give me as much aesthetic control, but still ultimately worked.
I used the LAS Dataset to Raster tool twice, first filtering to ground points for the Digital Elevation Map, and then to non-ground for the DSM. Using the Minus tool to subtracting the DEM from the DSM gave me a height raster with values ranging from around -5 to 163. This was the basis for the tree height map, and the DEM was a separate map.
I created a histogram from the height raster to analyze vegetation height distribution. I used “value” in the histogram after some trial and error.
I ran the LAS to Multipoint tool twice, for ground and vegetation. I used the average point spacing from the Point File Info table. The Gorund Multipoint filled the area completely, while the Vegetation multipoint didn’t’ fully render. However, once converted to a raster all the data was there.
I converted both multipoint layers to rasters using Point to Raster with a cell size of 3. Then I used IS NULL and Con tools to prep the rasters for analysis, followed by Plus, then Float, then Divide to find canopy density. Getting the correct version of each tool (Spatial Analyst version) was confusing, because several of these tools are named the same but with different descriptions (spatial analyst, image analyst, 3-d analysis, etc.)
In the final layouts, I made 3 final maps showing tree height, canopy density, and a DEM. I included the histogram in the tree height map per instructions, but I couldn’t figure out inserting a chart, it wouldn’t populate in any insert menus. I was finally able to do it by copying the chart and pasting directly to the map, which didn’t give me as much aesthetic control, but still ultimately worked.
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