This week's lab we covered choropleth mapping. Before I get into that part, I'd first like to share a bit about color ramps and their creation. Color ramps are comprised of colors which are composed of RGB (Red, Green, and Blue) these color values can be changed to create lighter and darker versions of a color. For example, when you increase the values together you get a lighter variation of that color and vice versa. Below you can see 3 variations of this: 2 I did on my own, and 1 generated by a software called Color Brewer.
As you can see, each progression has varying step values depending on what time of color ramp you were creating. Now that I've explained color ramps in some brief detail, let's see what they can be used for in GIS. Below is a Choropleth map of the population change in counties of Colorado from 2010 to 2014.
Within choropleth mapping, there are a variety of classification methods. For this map, I used the Equal Interval classification which creates equal class intervals. Additionally, I used a Blue to Red diverging color ramp, counties with the largest population decrease are darker blue while counties with the largest population increase are in a brighter red. Equal interval classification for this data be presented the total range and gave the 0% class a nice middle ground among the data without having to get too complicated in the manual classification.
~Map On!
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