Making maps, to present and display to others, is all well and good, but what of the context for the map's thematic content? Presenting information to an audience with a comprehensive understanding of the map's content, perhaps in the form of a presentation, can render the map itself a supporting visual aid. It is when the map stands alone, and is meant to be viewed and interpreted as a stand-alone visual, that the "infographic" can be an indispensable tool. Infographics add information that can be integral to understanding a thematic map's purpose, and can lend support to the map as an educational or explanatory visual. Though this information is, by necessity, often simplified and graphically embellished, it's a valuable tool for presentation nonetheless.
Above is a visual intended to convey the seriousness of the possible link between increasing rates of drug poisoning mortality and rates of uninsured adults. This is, by no means, extensive or scholarly research, but is rather intended to raise a question of whether this is an issue that may require more investigation. The maps, on the left, give an abridged picture of what the geographic distribution of the two factors- rates of drug poisoning mortality and percent of uninsured adults- currently looks like. The darker colored counties that are displayed as such in both maps are locations where prevalence of both factors is increased, which, as the other supporting graphics indicate, may be cause for some concern. The two charts on the right, a scatterplot showing the general relationship between the two variables, and a bar chart of where the five states with the highest percent of uninsured adults fall in relation to drug poisoning mortality average, summarize some of the quantifiable relationships immediately evident in the data. The graphics in the center give a few statistics that may support the contention that the relationship between the two variables is serious enough to warrant further investigation. The infographic, as a whole, sometimes tells more of a story than a map, displayed on its own, is capable of.
Maps which include 3-dimensional information are ubiquitous, and not just in the form of those that employ stereoscopic effects for the wearer of the right special glasses- 3 dimensions are regularly portrayed on a 2-dimensional surface with the use of contour lines, hillshading, and hypsometric tinting. The purpose of these techniques is to allow the viewer to more accurately visualize the varied elevations and land formations within the mapped area.
Hillshading, in particular, can provide a great deal of detailed visual information, which is readily apparent to even a map user unfamiliar with the finer points of deciphering contour lines. Above are two hillshaded images of the same overhead view- the left image is created with shading that imitates a light source located in approximately the sun's position for this area on the 15th of January at 8 am. The right uses the shading created by a light source in a particular position and elevation, one which is a default within ArcGIS. Thought these two images use the same color scheme- that is, the same colors in both for high and low elevation values- it's apparent that the visual images given by each are quite disparate. It could be contended that the image on the right, with the default light source position, gives a more readily interpreted picture. The depression in the terrain made by the canyon is immediately evident, outlined with the darker red/brown shadows in the mostly yellow terrain. The left image could easily be misinterpreted to be depicting a series of hills, in yellow, rising out of the terrain shaded in darker red/brown. Clearly, the light source's position is an important consideration in the creation of a hillshaded image- and is not always best-placed in the "accurate to earth" location.
No cartography education or body of knowledge is complete without the (seemingly) ubiquitous choropleth map- that which portrays a derived quantitative measure by some administrative unit. The map above displays the percent change in population for Georgia's counties, which includes both population gains, with positive percentage values, and population losses, which are shown with negative percentage values. The classification scheme used to group the counties according to their percent increase and decrease is the Natural Breaks method, slightly modified. This method gives a decent visual of where the county gains and losses were, without obscuring any patterns or trends, by maximizing the similarity of values within classes, and maximizing the differences between the classes. The colors chosen for each class use a diverging color ramp, where the lightness and saturation increase with the subsequent relative size of the population increase and decrease, which uses two different hues, in order to distinguish easily between gains and losses. Thus, the class directly in the middle represents counties with very little to no population change, and is the least saturated and lightest shade on the map. The legend itself gives indication of the value ranges for each class, with the average percent change at the bottom. The labels for "increase" and "decrease" are added with vertical orientation to the side of the classes, for an easy visual of the direction of the scale. The processes of normalizing derived data, evaluating thematic and data content, choosing effective colors and scale, and a plethora of other small decisions are integral to the construction of a functional and aesthetically pleasing choropleth map. These skills, in particular, form the foundation of an effective cartography skill set.
