The seventh lab of Cartographic Skills further explored the role one's choice of classification method plays in presenting data. Additionally, we explored the strengths and weaknesses of choropleth maps for communicating data. In the simplest of terms, a choropleth map features units shaded according to a value (e.g., population, median income). This seems simple enough, yet choropleth maps can easily misrepresent data if one isn't careful. To ensure data are represented accurately, they must be standardized. As an example: Rather than symbolizing a simple population count of a State, the population value could be divided by the state's area to get population per square mile (or whatever unit of measure one chooses). Another potential weakness of choropleth maps is the assumption that the represented values are homogeneous across each unit (e.g., assuming crime rates are constant throughout each state). Values may not be as uniform as represented.
The maps above were created using both ArcMap and Adobe Illustrator. After setting up the map in ArcMap (turning on State labels for the color map, choosing the natural breaks classification method, creating the legend, etc.), Illustrator was used to finalize the end product (adjusting the size and position of Alaska and Hawaii along with the State labels of New England, for example). The greyscale map was created mostly in Illustrator by converting the color map to grey and deciding the best way to classify each regional division based on calculations completed in Microsoft Excel. This map focuses on regional population trends as opposed to the more refined State level focus of the color map, although the latter also indicates similar regional trends.
No comments:
Post a Comment