ArcMap: Map Projections

Map Projections: The Good and the Bad

Working with ArcMap to explore different map projections made me understand the purpose and importance of map projections as well as the potential dangers. In this assignment, we used our basic knowledge of ArcMap to estimate the distance between Washington DC to Kabul using any six map projections (2 conformal, 2 equal area, and two equidistant). There are several stark differences between the projections I used. The most important one specific to this assignment is the different distances between Washington DC and Kabul depending on the projection used. It is clear that the distances vary from about 5069 miles using the Mercator projection to approximately 8763 miles using the Behrmann Equal Area Cylindrical projection. This discrepancy between projections is a big disadvantage when trying to measure the distance between two points. This can potentially be dangerous when planning travels or even secret missions between two places. 

Furthermore, another downside to map projections is that earth distortions are inevitable, meaning that there is not a single projection that retains all properties such as shape, area, direction, and distance. Hence, this can be very time-consuming when using projections being that different map projections must be used for different types of measurements needed.  This is especially important when looking at a small-scale map. The distortions can also be a negative because not everyone is familiar with all the different types of map projections. In fact, the Mercator projection is probably the one most people have seen while the Lambert Conformal Conic, the Two Point Equidistant, and the Equidistant Conic may look very foreign to many people.

Aside from the many downfalls, map projections are also very important. For instance, map projections are a necessary part of maps because the earth is a three-dimensional object that must be somehow displayed onto a two-dimensional surface. While distortions are always present, sometimes they are not important. For example, map projections are not important when looking at large scale maps. Furthermore, map projections have been categorized in such a way that it is convenient and easy to choose one in map making. When trying to preserve distance it is convenient to choose an equidistant projection. For preserving areas, it is smart to choose an equal area projection and for preserving angles locally, it is good to choose a conformal projection. Even within these useful categories, though, different projections provide more accuracy in other areas. For this particular assignment, it is probably more accurate to choose to use the equidistant projections because we are trying to measure the distance from Washington DC to Kabul. In fact, when looking at the Two Point Equidistant and Equidistant Conic, the discrepancy of the measured distance (6649 miles versus 6972 miles) is not as significant as when looking at the conformal projections or equal area projections.  

However there are even more advantages to map projections. As previously mentioned, without map projections, it is impossible to transform the three-dimensional earth into a two-dimensional map. Hence if we did not use projections, we would have to refer to a globe model to get measurements. However, there are many downsides to the globe that are in fact advantages of map projections. For instance, three-dimensional objects such as the globe are difficult to store and carry around. Also, even if we have a very large globe, it will always have a very small scale and hence it is difficult to see any detail. Furthermore, globes are very costly to make and difficult to update. These are all things that map projections make convenient to do. Specifically, map projections allow us to easily but carefully make maps that conveniently fit in pockets. Also, projections allow us to make very large scale maps that can show a small town with great detail. Lastly, maps are clearly cost-efficient and easy to update. 

 Referring back to ArcMap, it is a very useful tool to see the different types of projections. It was actually very easy to explore different projections and accurately portray the data. On another note, map projections themselves are a very powerful tool in society. They can easily manipulate people's minds. Using the example of the Mercator projection, Europe  and North America appear to be much larger than Africa. This projection, which is one that most of us grew up with, thus somehow gives more importance and power to Europe and North America to the rest of the world. This is an advantage of map projections as well as a peril. It is important to see that map projections can be used to make statements.