Module 4 - Color Concepts & Choropleth Mapping

 I'm not going to lie, but this week was a kind of difficult lab. Mainly from the perspective of choosing the correct colors, and color ramps to properly present the data. Choosing colors has not been my strong suit but this lab definitely opened my mind up to more ways of choosing them. The objective of this lab is to experiment with using color in ArcGIS Pro, prepare data for choropleth mapping, and to create meaningful choropleth maps for different types of quantitative data. The first thing I want to discuss with you is the differences between three color ramps, linear, adjusted, and ColorBrewer.

Linear                       Adjusted                  ColorBrewer 

The linear and adjusted progression color ramps are very consistent with their progression from dark to light. Linear though seems to cause the viewer to have a more difficult time discerning between some colors. This can be a result of uniform increments of RGB progression that potentially cause the appearance that colors are blending. The adjusted is a bit similar but the hue and saturation seem to be more discernable between the colors. The color brew ramp ensures that the hue, saturation, and brightness of the colors are balanced and the differences between the various colors are clear. Color brewer also ensures that the colors best convey the differences between each value. It avoids banding and gives a more natural feel to the viewer. Colorblindness is something that Colorbrewer tries to appeal to by ensuring that even for a color-blind user the colors are distinct. The linear and adjusted color ramps above would not be good for accessibility as it doesn’t conform to showcasing distinct differences as well as the colorbrewer does.

The next thing I want to discuss with you is Chloropeth mapping. We were tasked with taking data from the US counties data layer and choosing between the states of Colorado, Georgia, and North Dakota. I went with Colorado. The next step was to then normalize the data by calculating population change from 2010 to 2014 and using this formula: (new value - old value)/(old value)*100. Once the data was normalized I wanted to present my data via a natural breaks classification method because I wanted to ensure that the data properly showcased the natural distribution of data by following the natural changes. I used 6 classes to showcase an even distribution of positive and negative values, and I went with a blue-to-red color ramp to match that positive-to-negative connotation. I place my legend as a linear ramp that fills the bottom of the page to best fill the white space within the figure. I also made it so that the center of the legend was the center of the percentage values. Here is the resulting map: