The Coastal Ecosystem Mapping and Media Viability Project

Figure 12. Explanation figure to differentiate the Digital Surface Model (DSM) that shows change in elevation/pixel including features such as trees from the Digital Terrain Model (DTM) that shows change in elevation/pixel at the ground level, excluding above ground features. By subtracting the DTM from the DSM it is possible to create a raster dataset with tree height values that will be used to calculate mangrove tree volume. Although it is possible to also create a DTM output in Pix4D, it is still a beta tool, and thus far, outputs using that tool have been of very low quality. Therefore, we chose to use the DSM raster dataset supplemented with GPS elevation data, to create our own DTM of the study area. To create a DTM, we first mask the tree features from our DSM raster dataset using the Extract by Mask tool (spatial analyst => extraction) (figure 21).

Figure 27. DSM Raster dataset with NoData (white) values for where trees were originally located. The Extract by Mask tool was used to create this output.

The Coastal Ecosystem Mapping and Media Viability Project

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