Module 10 - Dot Density Mapping

This week we learned about dot density mapping, which describes a map that uses a dot symbol to show the presence of a feature or phenomenon. In this lab, we learned how to join spatial and tabular data, utilize dot density symbology and how to select a suitable dot size and unit value for our map. We learned about the advantages and disadvantages of dot density mapping and how to utilize mask functions in ArcMap to manipulate dot placement.

This week, we wanted to make a dot density map of the population density of south Florida. This map was created entirely using ArcMap. We wanted our final map to show the population density of urban areas of south Florida. I added the South Florida layer and used the join feature to join the data from the Excel sheet provided to the attribute table of the south Florida layer. I used the symbology feature to place the dots; I wanted to pick a dot size and value that would show the density properly without coalescing them too much, and ended up deciding on a dot size of 4 and a dot value of 20,000 (meaning 1 dot = 20,000 people). After adding the urban land and surface water layers to my map, I wanted to mask the dot map so that dots were only displayed in the urban land area. This is where I (and many others) ran into problems, because the mask always went back to the surface water layer. After reading the discussion board (and trying to avoid making a second .mxd if possible), I tried dragging the urban land layer to the top of the Table of Contents, thinking that ArcMap might be trying to draw the dots before the urban land layer. Not only did this work, I could then drag the south Florida layer back to the top without losing the mask. I labeled 4 of the larger cities and the largest lake in south Florida, and I turned off the county boundaries. I added another version of the south Florida layer underneath to give it a nice background color, and I gave the overall background a nice gradient fill color, which I feel helps make the map stand out. Below is my map of population density of south Florida.