Week 11 - Vector Analysis 2

This week we were doing more with vector analysis. This was a lab with a lot of new material. We learned about a couple of the more common modeling tools in ArcGIS, buffer and overlay. We learned about the dissolve tool, which merges overlapping borders of buffer zones. One of the most interesting aspects of this week's lab was learning about ArcPy and Python scripting to run the buffer tool. We learned about simple buffers and variable distance buffers. We learned about the 6 overlay operations available and when to use each one, and to convert between singlepart and multipart layers.

This lab was very interesting and I learned a lot about what kind of buffers to use and when. Our objective for this map was to show areas for potential new campground locations. One of our first buffers was on the Roads layer. We wanted our campground location to be within 300 meters of a road for ease of access. We also wanted our campground to be within 150 meters of a lake (for recreation) and within 500 meters of a river (a little further away to avoid pollution of the river and flooding of the campsite).

The first thing I did was to created the roads buffer and used dissolve to merge borders of overlapping buffer zones. For the water layer, I needed to use a variable distance buffer (lakes and rivers buffers are different distances), so I needed to insert a new field into the attribute table, select by attributes (to select lakes or rivers), and type in the desired buffer distance depending on the attribute. I created a buffer as described for the roads layer, this time using the "buffdist" field and the "List" dissolved type. At this point the lab assignment had us create different buffers at once using Python, which I feel is a very valuable time-saving tool. In both the water_buffer and road_buffer layers, I added a field that ends up having a value of "1" or "0". Basically, a "1" means that feature is within the buffer and a "0" means that it is not. Our campground needs to fit the requirements of both buffers, so I created a union between the two buffers; this layer indicates only features that follow the parameters of what we want concerning the road and water layers. Now I needed to consider the conservation areas, as we don't want a campground in these areas. I added that data layer and used the erase tool along with my union layer to exclude any conservation areas from my output. One final step was to convert from multipart to singlepart to show individual features on the attribute table. This layer is what is displayed on my map in dark green and satisfies all the conditions we want for our new campground. I then arranged my map and added the essential map elements. I used a rectangular gradient fill and drop shadows to give the map a better look.

This lab really packed a lot of information in and I learned a lot, especially about the variable distance buffers and using ArcPy. I appreciated that this lab made me think about why I was doing a certain step - I always had to think about what information the output was showing me, which is important when making a map. It's also useful (to me) to have a "reason" or a "project" (in this case sites for a new campground), as it helps me understand the concepts better.