Cartography: Module 7 – Choropleth and Proportional Symbol Mapping

     The aim of this laboratory exercise is to practice mapping a phenomenon using choropleth maps and subsequently symbolizing data using proportional symbols (in either a graduated or proportional manner). Choropleth maps are ideal for mapping a phenomenon that is uniform over an enumeration unit and that changes at an enumeration boundary. The data for this type of map must be standardized and can either be classed or unclassed. A color scheme is also employed in these types of maps. For the purposes of this lab, a sequential color scheme is used in conjunction with classed data. Three choropleth maps were created to represent several population phenomena for Europe. To practice with proportional symbols, wine consumption is also mapped.

     I completed the majority of the lab in ArcMap. I opted to make a custom symbol to represent wine consumption and designed this symbol in CorelDraw 7. I exported my symbol in a format that ArcMap could utilize (a .png image file and used RGB color settings) and imported that symbol using the Customize options within ArcMap.

A map displaying various choropleth maps for European
demographic data in addition to per capita wine consumption. 

     My map displays three different choropleth maps for Europe. Female and male population percentages are shown in the two smaller maps while the larger map shows population density and wine consumption per capita. The female and male population percentage maps employ a manual classification system with a pinkish-reddish color ramp. The manual classification scheme for both maps is based upon the natural breaks (Jenks) classification settings (with five classes). I adjusted the first class to include more data. That is, there were several countries that did not report their male and female population data. Thus, the first class initially included only those values reported as 0 (four countries). I thought the data was represented well when that first class was expanded. The same classification method is used for the female and male maps to make their comparisons equivalent and trend comparisons easier.

     Population density, in the larger map, is represented with a color ramp of bluish-green hues and a manual classification scheme. The classification is based upon the quantile method. The other classification schemes (natural breaks, equal area, and standard deviation) did not represent the data well. The manner in which the density data is distributed is such that most of the observations were included in the first class of either the natural breaks or equal area methods (and were within one standard deviation). This meant that one color (the single class containing the majority of the data) covered the majority of the map. As the quantile method puts an equal number of observations within each class, it lent itself better to this particular distribution. I then altered the upper limits of each class boundary slightly causing ArcMap to define my scheme as manual. I generated a unique symbol for wine consumption, an amphora, then imported this symbol into ArcMap. I chose graduated symbols over proportional symbols since the scale of the map is small. The proportional symbols obscured the smaller countries and while it may be a more accurate way of displaying data (does not class data into a range with an associated symbol like graduated symbology) it concealed too much. In  addition, I angled the symbols slightly to reduce some of the shrouding.

     Each map has an associated legend which display the color schemes as a contiguous unit. The graduated symbol legend is arranged with the smallest symbol at the top and the largest symbol at the bottom. A nested legend did not seem appropriate for pictographic symbols. A scale for each map is included as well as the projection used. For fun I am including iterations of the amphorae I attempted to use as well as the symbol I ultimately used.

The first amphora. The shading and lack
of outline made this difficult to use in ArcMap

The next attempt at symbolization.
The color choice was better but the lack
of an outline was still an issue.
Also, the handles on the side are too complex.  

Final symbol style.
The outline and color alterations
help the symbol stand out on the map.