The Coastal Ecosystem Mapping and Media Viability Project

Figure 31. Raster dataset with pixels having either tree height values or 0 (grey) if they do not overlap with tree features; output from the DSM - DTM calculations using Raster Calculator. Figure 25: Raster dataset with pixels having either tree height values or 0 (grey) if they do not overlap with tree features; output from the DSM - DTM calculations using Raster Calculator . Calculating Tree Volume After creating a raster dataset with tree height values, we calculate the mangrove trees’ base area values. The mangrove trees base area values can be simply computed using the “Calculate Geometry” tool in the attribute table of the mangrove tree polygon shapefile (figure 19). Using the Zonal Statistics tool with the statistics options as MEAN (spatial analyst => zonal), we then estimate the average value of each pixels from the tree height raster dataset (figure 25) that overlap with a tree feature from the mangrove tree polygon shapefile (figure 19). In the attribute table of the mangrove tree polygon shapefile, we now have two columns: one with the total area value for individual or cluster of tree feature, and another with their average height. To finalize our volume calculations, using the “Field Calculator” tool on a new field in the attribute table, we multiply values from the tree average height column with values from the tree base area value column to obtain volume estimates for each mangrove tree or cluster of mangrove trees features (figure 26).

The Coastal Ecosystem Mapping and Media Viability Project

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