This week's module involved examining RGB and HSV color ramps in ArcGIS Pro as well as exploring effective choropleth mapping. Three methods of creating color ramps were examined: linear progression, adjusted progression, and the website ColorBrewer.
Left to right: Linear progression, adjusted progression and ColorBrewer
The linear and adjusted progression color ramps are more mathematically consistent, following a uniform or modified stepwise increase in RGB values. In contrast, the ColorBrewer color ramp has non-uniform stepwise intervals, suggesting that ColorBrewer does not follow a mathematical pattern, but is instead designed in a way where the hues are easily distinguishable from one another. The ColorBrewer color ramp is visually distinct from the calculated progression ramps as its hues have greater contrast, which makes class distinctions clearer. The linear and adjusted color ramps appear visually similar, especially in the darker hues. The adjusted color ramp compensates for this with its increased intervals for darker hues, but does not have the same intentional hue contrast found in the ColorBrewer color ramp.
The last section of the module tasked us with creating a choropleth map of population change in a state of our choosing. I chose to map population change in Colorado, using the Natural Breaks method.
I chose Natural Breaks because the population-based data had natural variation with an uneven distribution of observations in the histogram. The Natural Breaks method considers how the data is clustered, which is useful in mapping data with natural variations. I chose a blue to red diverging color scheme and reversed the values to depict a gain (blue) to loss (scale). A blue to red color ramp allows for clear differentiation between increases and decreases and the colors blue and red suit the natural associations between gain and loss. I added Colorado's average population change for context, and changed the legend’s labels from “x% - x%” to “x% to x%” for readability.
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