GIS4043 - Week 10 - Vector Analysis Part 2

Potential Campsites In DeSoto National Forest, MS

In the second phase of our understanding Vector Analysis we were tasked with taking features from a provided geodatabase and creating a map of potential campsites.  We applied different analysis tools to a vector layer (Roads) and a polygon layer (Water) to create buffer zones or areas within a certain range of a feature.  The first analysis tool was the Buffer tool.   Per the lab instructions we created road buffer zones of various distances (100 meters - 300 meters).   We later used only the 300 meter road buffer zone layer to further develop our map.  In order to create these road buffer layers we used two methods, the first method used a fixed distance or linear unit to define the buffer zone.   Later we created road buffer zone layers by using Python scripts (arcpy) to create multiple processes at once.   By simply using copy/paste we could create buffer zones for the road layer of different set distances (100, 200, 250, 300).  We also used the Buffer tool to create a variable distance buffer for the Water layer.   We had two types of water features, rivers and lakes.   The lab required different buffer distances for each water type.   Rivers had a buffer distance of 500M and Lakes had a buffer distance of 150M.  This method required that we create a new field in the Water attribute table called buffdist (buffer distance) and assign the different distance values according to the water type (river, lake).

Next, we used Overlay tools to combine feature attributes of input layers to create new output layers.  Specifically, the lab used the Union tool to preserve all of the features in both input layers to create a new output layer.   Our input layers were the Water_Buffer layer we created with the varying buffer distances per water type, and the Roads_Buff300M layer which was our road buffer of 300 meters.  This union created an output layer with nine records.   From this output layer we then narrowed our selection by choosing records that only resided within our road buffer (300M) and our water buffer (150M and/or 500M).   This new Buffer_Union_Export layer became our input layer to create Possible_Sites, a layer of potential campsites.   After adding the provided conservation_areas feature class to the map, I then used the "Erase" overlay tool to exclude any conservation areas from our Buffer_Union_Export layer.   This newly created Possible_Sites layer was complete however, we could not view individual polygons (campsites) because features had been grouped together into a multipart layer.   We used the Data Management Tool, multipart to singlepart to create single polygon records, campsites.   Using this final singlepart layer I created a final map highlighting these potential campsites that met our site requirements of being located within 300 meters of a road and within our water buffer zone (150 meters of a lake and/or 500 meters of a river).  I used a World Terrain basemap underneath the feature data as well as for an inset map for reference of the location, DeSoto National Forest, Mississippi.

This assignment was a challenge for me mainly because of some ArcMap difficulties in exporting and saving files to an existing database.   I learned a work around to schema lock error messages (create shapefile and import shapefile into geodatabase).  I also had to take time to thoughtfully understand the overlay tools and the output layers they actually created from the input layer(s).   Creating a description field really helped me visually see what features were combined, excluded, etc.