Maps

There are many different kinds of maps that show geographical patterns. In all types, a good map must have a title and a key, as well as a scale and an indication of north. Beyond these basic standards, five specific types, which will be explained below, are the choropleth map, the dot density map, the isopleth map, the proportional symbol map, and the environmental sensitivity map.

The choropleth map is the most common of the geographical statistical maps. This type uses different colors, or different shades of the same color, to indicate high, medium, and low areas of the data being displayed. It is most often used to display data regarding rates, densities, and percentages.  This example of a choropleth map, pictured above, shows diabetes hospitalization rates in Massachusetts by ethnicity. As the key shows, this map indicates that the darker the area, the more hospitalizations due to diabetes in that region.

The dot density map, as the name would indicate, uses dots to show geographical patterns. Individual data points are shown on these maps using a dot, and when all the dots are on the map together the patterns and clusters of the data are easily visible. The dot density map above shows the houses built in West Virginia during or before 1935. The clustering of the dots make it easy to see in which parts of West Virginia there are the most of these old houses.

The isopleth map, sometimes called the isoline map, portrays continuous distribution using lines. These lines, called isolines, connect to show ranges of equal value. Most often, this type of map is used to show temperature or elevation. The example above uses lines, as well as color, to map out the average maximum temperature across Ohio from 1971 to 2000. While the various shades of red indicate various temperatures, the lines are also marked with different temperatures, making it an isopleth map.

The proportional symbol map quite simply uses symbols that are proportional to the data being displayed. For example, if the symbol being used was a circle then a larger circle would indicate a larger value of the date, whereas a smaller circle would indicate a smaller value. Any sort of symbol can be used on this type of map, such as a circle, a square, or even a symbol specifically related to the data being considered. In the example shown above, circles of varying sizes are used to show the number of traffic fatalities in each state in 2009. As is shown, the larger the circle is the more fatalities that state had in that year.

Finally, the environmental sensitivity map shows the environmental and cultural aspects in a specific region. This type of map takes multiple datasets and combines them into one to show the areas of a region most sensitive to development due to the resources or other assets present. These assets can include anything from national parks to simply biodiversity.  The environmental sensitivity map above shows the Hudson River in New York.  While a bit difficult to see due to size, this map shows the different species found around this river, as well as the different human resources that can be found.

In addition, here is a video from National Geographic that shows the destructive powers of a hurricane.

Sources:

“Environmental Sensitivity Mapping." British Geological Survey (BGS). Web. 04 Sept. 2012. <http://www.bgs.ac.uk/mineralsuk/sustainability/mapping.html>.

"Neighborhood Statistics." Office for National Statistics. Web. <http://www.neighbourhood.statistics.gov.uk/HTMLDocs/images/Statistical%20Maps%20-%20Best%20Practice%20v5_tcm97-51126.pdf>.

"Types of Thematic Maps." Types of Thematic Maps. Web. 04 Sept. 2012. http://srufaculty.sru.edu/james.hughes/100/100-1/d-1-12.htm