Lab 5: Map Projections

Equidistant Map Projection

Equal Area Map Projection
Conformal Map Projection

This lab assignment was a good learning experience because experimenting with the different types of map projections provided me with a better understanding of them. Patterns were noticed between conformal, equal area, and equidistant maps which emphasized the purpose of each map projection. For example, the latitude lines of both equidistant projections are evenly spaced which isn't true of the conformal or equal area map projections near the Earth's poles. Distortion is apparent in many of the examples shown above (i.e. Cylindrical Equal Area and Mercator) which drastically changed the distance between Washington D.C. and Kabul from the other map projections. Each projection has the miles separating Washington D.C. from Kabul in its title. As expected, the equidistant maps have the smallest change in distance between the two examples.

Each map projection has a purpose: conformal maps maintain angular relations, equal area maps maintain area, equidistant maps maintain distance. Specified purposes are made easier through ArcGIS because all of the information can be stored digitally instead of on multiple paper maps. Furthermore, having different map projections saves time and eliminates some uncertainty for the viewer. For example, the equidistant maps shown above have the smallest difference in distance from Washington D.C. to Kabul than the conformal or equal area maps. This demonstrates the purpose of equidistant maps, though I believe the measurement performed in ArcGIS was inaccurate.

The biggest problems with different types of map projections include similar reference points and similar geometric projections. Conformal, equal area, and equidistant map projections maintain their specific features from a given reference point. If this reference point is changed between maps, the feature that should be maintained will be skewed (i.e. the distance from Washington D.C. to Kabul). I don't know if it was possible to make our own reference points in this assignment, so I assume this wasn't a major issue.

Similar geometric projections were an issue in this assignment. Most map projections were cylindrical and therefore had a rectangular shape, but some map projections weren't cylindrical. I think the ArcGIS measuring tool altered the distance between the two cities on these maps. For example, the distance on the equidistant conic map wasn't measured parallel to the latitude lines like the equidistant cylindrical map was. I believe this resulted in the 2000 mile difference between the two projections.