Lab 3

This lab exercise helped to reveal the strengths and weaknesses of various map projections by providing a good way to compare them together at one time. While map projections are designed to preserve a particular aspect of the map while allowing distortions in other aspects, this exercise also showed that there are many differences between even the same types of projections.

While it is common for conformal maps to distort area sizes near the poles, the two projections used in this exercise show significant differences in their distortion near the poles. A clear example of the distortion can be seen by comparing the distances between the 60 degree latitude lines and the poles. The Mercator projection stretches these areas of the globe so much that the scale of the Mercator map is twice as small as the Stereographic map, but the mapped areas are nearly the same size. This shows why conformal maps are not ideal for thematic maps which compare data distributions, especially if the mapped area involves latitudes outside of the tropics.

The equal area projections proved that they also distort shape and distance, like the conformal projections. Unlike the conic equal area projections for North America, these global equal area projections would not be optimal for thematic maps either. Though they would offer an accurate comparison of the data distribution due to the preserved area sizes, these projections distort the shapes of many countries from the shapes people are accustomed to seeing.

The equidistant projections present perhaps the greatest pitfalls. Since they are designed merely to preserve distances from all points to one particular point, they do not necessarily preserve distances between any point and any other point. I think a map user who did not understand that could potentially assume the equidistant maps preserved all distances. Clearly, the Equidistant Cylindrical projection displays an incorrect distance between Washington and Kabul. Additionally, this particular projection shares many of the shortcomings of the conformal maps. While the conic projection was very close to the actual distance of ~6919 miles with this particular example, its major weakness comes in the massive distortions of shape and area in the southern latitudes.

This exercise reveals why it is important to select a proper projection to fit the purpose of the map. The differences in projections offer a variety of strengths to be exploited and weaknesses to be avoided when creating a map.