Map Projections (Lab3)

Understanding map projection is very important because each projection has benefits and drawbacks. There is no such thing as a perfect projection for a world map because flat world maps are fundamentally imperfect. Projecting the irregular sphere of the earth onto a flat map requires compromise. Every time the earth is projected onto a flat surface, the properties of shape, area, distance, direction, baring, and scale can be distorted. Which map projection we choose is determined by the properties we most need the map to preserve.

For my conformal projections, I used Mercator and Gall Stereographic. Conformal projections are designed to preserve angles locally. For the Mercator projection, I measured 10,125 miles between Washington D.C. and Kabul Afghanistan. On the other hand, I measured 7171 miles between Washington D.C. and Kabul in the Gall stereographic projection. There is clearly a massive disparity between the two projections in terms of the distance between the two cities. The actual distance between the two cities is about 6922, so the Gall Stereographic comes much closer to the great circle distance.

I used the Hammer Aitoff projection and the Sinusoidal projection for my equal-area page. These projections are designed to preserve area. Therefore, these projections are useful when we need to calculate land area. I measured 8316 miles between Washington D.C. and Kabul when using the Hammer Aitoff projection. On the other hand, I measured 8114 miles between Washington D.C and Kabul with the Sinusoidal projection. Again, these projections both overstate the distance between the two cities.

Finally, for my equidistant projections, I used Plate Carrée and Equidistant Conic Projections. These projections produced curious results. This is because I measured 10,120 miles between the two cities in the Plate Carrée, while I measured 7010 miles in the Equidistant Conic. The Equidistant Conic projection comes very close to the actual distance. However, the Plate Carrée projection is far from the correct distance. Out of all of the projections I used, the Equidistant Conic does the best job by far of approximating the distance between Washington D.C. and Kabul Afghanistan. It makes me wonder if the Plate Carrée projection in ArcMap is truly equidistant because it does such a poor job of preserving distance.