Tuesday, February 21, 2017

Choropleth Mapping

Choropleth mapping is a common mapping style which allows a GIS user to display data over a wide area. Choropleth maps are used to display a particular field (or fields in some cases) against a color gradient. These maps are often used to show changes in data such as population changes.

For this week we were tasked in creating a Choropleth map for a state of our choosing using the change in population on the county level from the year 2010 to 2014. Here is my final product:

My main goal with this map was to make everything as easy as possible to read. There are a lot of variables to be considered with this type of map. Things such as the class breaks for the data and the color scale used to display it are all factors that can have a huge impact on the final map.

For my data breaks, I used a defined break classification system were I made each of the classes have a data range of 5%. ArcGIS will then auto create the right number of classes needed to display all of the data with the given range, in this case that was 6.

My focus after that was to make sure the map flowed well. I used colorbrewer2.org/ to create an appropriate color scale that would allow my data classes to have enough separation from one another and also be easily distinguishable.

Arguably the most important part was the legend. I made sure to make it easily understandable and also on the same plane as the rest of the map, hence why it is in the main data frame. The legend title directly corresponds with what the data represents so that there is little to no confusion for the reader.

After that, all I needed to do was to make sure everything else looked good for a publishable map. I made the rest of the United States a background feature and made the frame background a light blue color to represent the Atlantic Ocean.

Overall, I am very proud of this map and it will definitely be going into my map portfolio!

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