Week 7: Map Projections

For this lab exercise, I created six different map projections of the world, and each gave dramatically different distances for the line between Kabul, Afghanistan and Washington, D.C. The standard true distance is 6,934.48 miles, but the fact that each projection had different distances from this shows that map projections cannot be trusted too easily and whoever uses them must be wary of the kind of distortion involved. It seems peculiar to me how each projection can really only be used for a specific, narrow purpose, since each projection differs in where and how it decides to allow distortion. This means that whoever references a map must be extremely careful in identifying the map's projection and must be aware of where and how the distortion is distributed to avoid making drastic errors in measurements.

 

For the equidistant map projections, I chose the Azimuthal since it is used in the United Nations logo, as well as the equidistant cylindrical. It is true that the equidistant projections are perhaps better for maintaining scale throughout the map, but evidently by looking at the Azimuthal projection and the equidistant cylindrical projection, even they are not the same in terms of distance. For example, the distance between Kabul and Washington, D.C. is three thousand more miles in the Azimuthal projection. Thus it is a disadvantage inherent in the map that distance is only true in relation to the center point, but not to all other points. Also, there is more and more distortion of shape and area going along the latitude lines as you move along the map away from the center of the projection. For example, in the Azimuthal projection, Australia and nearby Pacific Islands are stretched far beyond their original shape because they are far from the center point of the map.

The equal area map projections are best for showing the actual size of the land masses. I personally prefer equal area map projections most because they show how large each land mass is in relation to the other land masses, and thus show how things really are in relation to each other. I prefer the Mollewide projection in particular because it also preserves distance and shape relatively well, and it visually resembles the compromise and trusted Robinson projection. I admire how the Bonne map has the distance between Kabul and Washington, D.C. that is closest to the standard distance, but it has a downside in that it severely distorts the shape of the land masses to the point where even some of them are hard to see, such as Australia.

It was interesting but not surprising that the conformal map projections had the distances between Kabul and Washington, D.C. that was most different from the standard distance. Conformal projections probably have the most distortion out of all the map projection types because they do not attempt to preserve any kind of true measurement. It is understandable why elementary schools like to use conformal projections, like the Mercator, to teach children about the world and what it looks like, but evidently we can see that such projections dramatically distort size. It seems though as if the Mercator projection is preferable over the stereographic projection, however, if you care more about equal area, since the stereographic projection severely distorts the size of all land that is far away from the center point of the map: namely, everything besides Africa and the Middle East. The Mercator is more preferable because it distorts while moving away from a line (the equator) rather than a single point, therefore having severe distortion over a smaller area.

It is lucky, however, that most maps are of a larger scale than world maps and cover less area, thus minimizing the amount of distortion involved. It is mostly only when dealing with world maps do we encounter distortion to worry about.