Lab 5

The focus of this week’s lab assignment was map projections and the various forms that they exist in. The creation of a map projection is a complex science. One must take the geographic features of an oblate ellipsoidal earth and represent those features on a flat surface. This transference creates distortions and as such all maps have distortions. Within map projections, distortions usually come in the form of equal area versus true shape. When a projection holds one property true the other is sacrificed to varying degrees. Therefore, a map projection should be chosen based on its intended use.

For this lab, I created three posters in ArcMap displaying three categories of maps, with two examples of the categories. Each map is focused on the same general area with the same two cities marked (Washington, DC and Kabul, Afghanistan) to highlight the distortions from one to the other. I worked with and altered three layers of data to illustrate what I wanted my maps to feature. From there I used the measuring tool to determine the distance from Washington DC to Kabul and displayed that information on the maps for reference. I also added a scale bar and a scale fraction to each map. Finally, I arranged the layout and adjusted the background to map the posters more appealing to the the eye.

The first category of projection presented is Equidistant Maps, with a Sinusoidal and an Equidistant Cylindrical map as the examples. Equidistant maps preserve the distance of a standardized point of reference. The second category is Conformal Maps, with a Mercator and a Stereographic map as examples. Conformal maps preserve angles in the area of focus. The third and final category is Equal-Area maps, with a Bonne and a Goode’s Homoiosine map as the examples. Equal Area maps preserve true area. Some of my example, like the Mercator, are far more common map projections than others, like the Boone projection.

The distortions in these examples can most easily be observed in the shape and size of Earth’s landmasses. South America, for example, changes greatly in size and shape from one map to another. In the Mercator map it appears to be less than Greenland in area and one of the smallest continents in general. In the Stereograpic map, South America and Australia appear to be just off the coast of one another. Distortions in map projections are very important when judging distance. Each map contained within in my posters has the distance from Washington DC to Kabul in miles included in the map data. The distance varies from 5,000 miles in the Equidistant Cylindrical to 10,000 miles in the Mercator. This is an extreme fluctuation.

 

Map projections are an extremely useful tool when studying the Earth and all of its attributes. However, the distortions must be taken into account when viewing the map and judging distance, shape, and area.