Week 10 - Vector Analysis 2

The purpose of this week's lab was to explore the most common modeling tools in ArcGIS - buffer and overlay - and create a script in ArcPy for the buffer tool to combine or exclude multiple vector features. The resulting map includes final possible campsite areas, after applying the overlay tools.  

First, I used the Buffer tool to create a feature class with a fixed distance. The resulting feature class included areas within 300 meters of roads, dissolving all buffer borders so that areas of overlap were merged. 

Next, I created a feature class with a variable distance from the water features (150 m for lakes and 500 m for rivers). To do this, I added a field to the attribute table of the water feature that included the desired buffer distance for each feature type, and then I used the Buffer tool with these fields as the buffer distance and dissolve type. I also used ArcPy to create a script to use the Buffer tool to create feature classes with variable buffer distances from the roads feature class. 

Next, I used the Union tool to merge the roads buffer and water buffer feature classes. Before using this tool, I prepared the buffer layers by adding a field to each attribute table defining the areas near the roads and water. These fields were called "insd_rbuf" and "insd_wbuf", respectively, and assigned a value of 1, i.e. "yes." I used the Union tool to combine the buffer areas. I then selected the records where the "insd_" fields equaled 1 in the resulting union and created a feature class from the selection. 

Finally, to exclude areas within conservation areas from the new union feature class, I used the Erase tool. The resulting feature class was a multipart layer, meaning that selecting one polygon, selected many features in the layer. I preferred to isolate each polygon within the layer, which meant creating a singlepart layer. To do this, I used the Mutltipart to Singlepart tool. In addition, I added an Area field to the final attribute table and used the Calculate Geometry function to calculate the area in hectares for all the polygons in the final layer.

Because the final map represents possible campsites between two wilderness areas and the likely audience for the map would be outdoor enthusiasts interested in the topography of the area, I elected to use a USA Topo Map as the basemap.

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