Lab 5: Projections in ArcGIS

Conformal Map Projections



Mercator Projection



Distance from Washington D.C. to Kabul: 10,119 miles

Gall Stereographic Projection



Distance from Washington D.C. to Kabul: 7,155 miles

Equal Area Projections


Cylindrical Equal Area Projection




Distance from Washington D.C. to Kabul: 10,140 miles

Mollweide Projection




Distance from Washington D.C. to Kabul: 7,953 miles

Equidistant Projections


Plate Carree Projection




Distance from Washington D.C. to Kabul: 10,111 miles

Sinusoidal Projection



Distance from Washington D.C. to Kabul: 8,030 miles

This lab exercise was incredibly interesting as I got the chance to manipulate maps in different ways using different projections. It is fascinating to observe the transformation of the globe according to the certain and unique parameters of different projections. However, as interesting as this technique is, many pitfalls exist within the realm of map projections. As soon as I made my first map projection, I immediately observed and understood the primary pitfall - distortion. However, map projections also provide several benefits to modern GIS and cartography. Projections allow us a way to display the three-dimensional Earth on a two-dimensional plane.

There are three kinds of projections - conformal map projections, equal area map projections, and equidistant map projections. Each of these projections serves a specific purpose. For instance, conformal projections preserve the local angles, thus making them incredibly useful for navigational purposes. The conformal projections I display above are the Mercator projection and the Gall Stereographic projection. Equal area projections preserve area. Thus, these projections are best used for calculating areas of regions and countries. The equal area projections I have displayed are the Mollweide projection and the Cylindrical Equal Area projection. Finally, equidistant projections preserve distances, making them the best projections to use when calculating distances between two fixed points. The equidistant projections I have displayed above are the Sinusoidal projection and the Plate Carree projection.

Projections have numerous pitfalls that cannot be easily overcome. First of all, there is no perfect projection. Some are better than others, but this depends primarily on how the user needs to manipulate the data. Most of these pitfalls emerge from the issue of distortion. A prime example of distortion is the large size of the northern hemisphere on the Mercator projection compared with the small size of the southern hemisphere. Each type of projection will manipulate the map and image in a different way, thus making it incredibly difficult to achieve uniformity. This becomes clear when calculating the distance between Washington D.C. and Kabul, Afghanistan on each of the six projections. Every map delivered a different answer, and almost none were even remotely close to one another.

However, despite the pitfalls, projections have definite potential. For instance, projections allow us to display the three dimensional world in two dimensions. Also, each projection allows us to view the world with a different perspective from what we are ordinarily used to. Map projections allow for easy navigation across the oceans, simple calculations of area, and accurate calculations of distance between points. The key is to use the correct type projection for each, separate need. Projections also allow us to model data, such as the melting of the polar ice cap. Overall, the benefits and potential of projections far outweigh the pitfalls.