Projections 101

Map Projections 101 Report

This lab demonstrates the significance of map projections and how different projections can show you very different representations of the world. Since we are trying to make an accurate two dimensional model of the Earth, which is three dimensional, selecting the correct type of map projection requires consideration of what is the purpose of the map. Since every projection causes some distortion, some projections more so than others, making the correct choice of map projection should be determined by what type of information is hoped to be derived from the map.

In our case for this lab, we wanted to figure out the distance between Washington D.C. and Baghdad, Iraq. When each of the six different map projections were applied to our original map, it yielded very different results when determining the distance between these two cities. The conformal projections had drastically different measurements, with the Mercator projection stating 8,414.87 miles from Washington D.C. to Baghdad and the Gall Stereographic projection stating 5,951.85. The equal area Bonne and Sinusoidal projections showed 6,103.85 miles and 6,732.92 miles between the cities while the equidistant projections Plate Carree and Equidistant Conic measured the distance to be 8,410.27 miles and 6,266.63 miles. I went online and looked up the distance between Washington D.C. to Baghdad on www.timeanddate.com and it said that the shortest distance between these cities is 6213 miles. If this data is correct, it suggests that the Equidistant Conic and Bonne map projections are the most accurate.

When looking at these six different projections we can see the various degrees of distortion. The conformal projections seem to maintain more accuracy in displaying the land found closer to the equator, however towards the poles there is significant distortion--Greenland is much too large and Antarctica is humungous. Between the two conformal projections, the Gall Stereographic projection is a better map projection than the Mercator, especially for our purpose in determining the distance between Washington D.C. and Baghdad. Of the equal area projections, the Bonne projection significantly distorted some landmasses such as Australia which is shown to be much larger than it is. Also land towards the North Pole, specifically Greenland, Russia, and Canada, are proportionally much smaller to the than they are in actuality. Nonetheless, land nearer the equator seems to be more accurately preserved and thus the Bonne projection provided us with the most accurate distance between our selected cities. Finally the equidistant projections provided us some of the best and worst measured distances between Washington D.C. and Baghdad. The Plate Carree projection looks strangely warped with the southern hemisphere larger than normal while the northern hemisphere is shrunk, which probably contributes to the great exaggeration of the distance between our selected cities. The Equidistant Conic projection, like the Mercator, shows Antarctica to be too great in size, yet nonetheless provides us with a relatively accurate distance between Washington D.C. and Baghdad.

Ultimately choosing the correct map projection to use requires one to determine which projection will display the best results in answering the given question. Since map projections can distort shape, area, distance, and direction, it is important to identify the projection that will provide the least amount of distortion to properly display a map suitable to answer the given question. Thus in our case, since our question was in regards to distance, choosing a map projection that distorted distance the least was most important in answering our question. Though having a map that does not distort everything else too much is still important, preserving distance was first to shape, area, and direction.