Lab 8

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Lab 8 Information

The intent of this lab was to advertise GIS in a creative way, using at least two data sets and two data processing tools. I used this week's lab to make fun of my home state, and symbolize mean speed limit and total length of paved roads within each Wisconsin county.

First, I downloaded Wisconsin shapefiles for this project from a couple places and used them for the following:

• Wisconsin road speed limits (http://download.geofabrik.de)

I used this to calculate the mean speed limit within each county.

• Wisconsin road polyline (http://download.geofabrik.de)

I used this to calculate total road length within each county and to symbolize the roads on the final map.

• Wisconsin county boundaries (https://www2.census.gov/)

This layer served as the boundaries the road length and mean speed limits were calculated within, and I used it to symbolize the counties on the final map.

To actually do the calculations mentioned above, I used two ArcGIS Pro tools:

• Clip

I used the Clip tool to clip the road polyline layer to the Wisconsin county boundaries, because it had some roads that bled over into Minnesota and Michigan. Any roads that fell outside the Wisconsin layer were removed and a new polyline layer was created of just the roads that fell within the Wisconsin boundary. This served to make the final map cleaner, and potentially corrected any length and mean speed limit calculations. I was already aware of this tool from earlier lectures, so it was an easy choice to include in my workflow.

• Summarize Within

The Summarize Within tool summarizes a layer based on the boundaries of a user-selected polygon shapefile. I used it here with the Wisconsin county boundaries and summarized the total length of roads and the mean speed limit within each county. Summarize Within outputs a new polygon with the same geometry as the input polygon, with the calculated summaries in the attribute table. This means you can symbolize the calculated values using color gradients, patterns, etc. within the original polygon's boundaries. I found this tool using a Google search because I knew there should be a way to summarize one layer with another's geometry, but I couldn't figure out how to do it by browsing through the ArcGIS Pro tools.

Once I ran the tools and got the output summary data and polygons I needed for my map, I symbolized the data in a way that made sense to me and I thought looked nice by doing the following:

• I symbolized the mean speed limit in each county with a gradient color scale, using a single symbol (not "symbolize unique values"), but then told ArcGIS Pro to use a gradient in the "Vary symbology by attribute" pane.

• I symbolized the total length of roads in each county with a dot within each county boundary scaled to represent total road length as compared to the other counties, using "Proportional Symbols" under "Symbolize your layer by quantity" in the symbology drop down menu.

From there, I added text to the map, created a legend in Photoshop (this week I couldn't get the legend to play nice, so I opted for an outside graphics program), and exported the map in .png and .pdf format.

Additional Downloads

High resolution (PDF) download available here