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Post date: Sep 27, 2015 4:21:1 PM
A major portion of our project will revolve around displaying data and information on maps. Since we're going to be working with information that is separated by geographic region, this blog post will focus on the types of maps used for displaying data based on geography.
Choropleth Maps
One common method for displaying data by geographic region is a choropleth map. Choropleth maps are used to display data on a single variable. Each geographic region in a choropleth map is shaded based on the amount of the variable that it contains in proportion to the total count of the variable contained in the map.
One of the issues associated with choropleth maps is that regional shading may be skewed based on overall density of the variable being measured. For example, the map shown to the left may have a low overall median household income in Mississippi, but the state could have localized geographic regions with much higher median household income. These regions won't appear on a map with areas shaded by state.
Mesh Maps
A mesh map, as shown to the left, represents data using the same type of intensity scale as a choropleth map, but each shaded region is defined by a much smaller grid size.
Mesh maps are useful replacements for choropleth maps when representing data in regions that have low overall densities of data points with localized hotspots. For example, a mesh map of the state of Mississippi set to a 1-mile grid may reveal areas with high estimated median household income that don't appear on the choropleth map shown above.
Heat Maps
A heat map is based on the same principles as both choropleth and mesh maps, but operates on a much finer scale. Heat maps are used to show levels of data occurrences in a geographic area. This type of map makes it easy to pinpoint geographic locations with high or low occurrences of data. These maps are also shaded in their entirety, and are not divided up by region or spatial grid like choropleth and mesh maps.
Other Map Types
There are also several other useful methods for displaying geographic data. These include but are not limited to:
Proximal, or 'Radius' mapping, which is used to visualize how much of one variable is located within a certain radius of another. For example, a proximal map could be useful for showing hotels located within a ten mile radius of each airport in Massachusetts.
Pin maps are one of the most common type of maps on the internet, and show pins at the location of certain objects of interest. For example, if you were to search for Dunkin Donuts in Worcester MA in Google Maps, you'd end up with a map of Worcester that has a 'pin' at the location of each Dunkin Donuts resturant.
Bubble maps are based on the same principles as pin maps, and display 'bubbles' in set geographic regions that are scaled based on the number of data points in their region.
User Interactivity
Although all of the map types mentioned are extremely useful for displaying information on one or two variables, representing more complex sets of data and information is almost impossible to do without some element of interaction. An excellent example of an interactive map is the 2011 New York Times visuialization of The Geography of [US] Government Benifits. At the base level, this interactive mapping tool contains a choropleth map of the United States. Added user interactivity allows for the map to display multiple variables worth of data, and gives the user the ability to observe trends over time at a regional level.
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