Lab 5: Projections in ArcGIS

The only thing changed in this lab is the map above. I lost my old map (a file saving error) and produced this one according to the criticisms from my last map below. Thanks!






This week's lab was very interesting, being that we had to use ArcGIS to create the "same" map, just with different projections. From the outside, it sounds easy to just create 6 maps with different projections, while in reality it was hardly that. This weeks lab was challenging for me in terms of creating a "pretty" format, but using the tools and skills I acquired in last weeks lab, it was much easier. Using last weeks skills, I created a map with different layers and used 6 different projections (2 conformal, 2 equidistant, and 2 equal area) and then measured the distances between 2 set points (Washington D.C. and Kabul, Afghanistan).

Map projections are important for a variety of reasons because they take a 3D earth and turn it into a 2D projection. Topography is the study of the earths surface, shape, and features and the map projections can preserve area (equal-area), distance (equi-distant) and angle/direction (conformal). Conformal maps will preserve direction and angle, equal area maps will preserve area, and equidistant maps will preserve distances between two points. Depending on the region of interest for the map user, we can tailor a map projection to make some features more accurate and less distorted. The first reason as to why map projections are important is because the distances between 2 points are different depending on what map projection you use and what datum you use. As you can see above, even with the same projection (for example conformal), the distances can vary by 200 miles. In the conformal case, I used the Mercator and Canada Lamber Conformal Conic and the distances were different to the tune of 199.2 miles!

When I created the map projections for equidistance, I purposely used two different datums that were across the world from each other so I could better see how different datums effected different projections. As you can see above, by using the equidistant conic, one from North America and the other from Asia, the distances between Washington D.C. and Kabul, Afghanistan were off by 161.8 miles! That is a significant distance (around 2.5% of total distance traveled between those two points), and interesting since one would think that all equidistant maps would give the same distances between two points. The reason why I believe the distances between these two maps are different are because of the different datums being used. As a pilot or someone that works in the aerospace industry, this difference just in using the correct data is very important in seeing how long a trip is going to be and even how much fuel to put in the aircraft tank so it doesn't run out of energy! It should be noted, however, that the equidistant maps were more similar in distance to each other than the other 2 projections.

Lastly, I thought the map projection of the US National Atlas Equal Distance was interesting because of the spherical look of the projection, almost preserving the same of the earth. When this map projection was compared with the Canada Albers Equal Area Conic, the distances between the two cities of note was the greatest of the three map projections, 640 miles. This is important to note because even though the two datum are from the same hemisphere, the distances are significantly different between the two points.