Lab5: Projections in ArcGIS

This lab exercise greatly demonstrated the importance of map projections. First thing I noticed was the distortions present on each map. Because the world is in three dimensions, and maps are in two dimensions, distortions exist when projecting the world onto a map. There exist three major categories of projection (based on the geometric properties they keep): Conformal, Equal Area, Equidistant. Conformal map projections preserve angles locally; examples are Mercator and Eckert I. Equal Area map projections preserve area; examples are Goodes Homolosine and Bonne. Equidistant map projections preserve distance from some standard point or line; examples include Azimuthal equidistant and Two-point equidistant.

The most important thing when looking at a map is to find out which of those properties the map keeps; this helps the understanding of the purpose behind the map and can be utilized accordingly. For example Mercator and Eckert I, conformal maps which keeps the angles are suited for navigations rather than settling area disputes (Antartica looks bigger than the other continents combined on the Mercator projection). For a dispute regarding area, Equal Area projections are much more suited than other projections. Goodes Homolosine shows the continent of Africa is bigger than Antarctica unlike on the Mercator projection. The Equidistant map keeps equal distance properties based off of its set standard, so it is not suited for measuring distance from one random point to another on the map, but rather is used for more specific measurements related to that standard.

While trying to find the distance between the two cities, Washington D.C. and Kabul, I found out that these distortions caused a great deal of errors. For example, a straight line distance on a Mercator projection (Conformal) was about 10,112 miles, when the correct distance is 6,934 miles. None of the six maps gave a close enough measurement in straight line. The lack of this knowledge can potentially cause great disaster. With the increasing prevalence of amateur uses of maps, the danger for spread of wrong information through the web without any authoritative verification increases.

I think the equidistant maps best demonstrate the purpose of this lab. To use the maps based on the purpose and the properties they are meant to be used for. Equidistant projections, for example have such a specific usage that it did not seem logical to me what the name “equidistant” meant at first. They exemplify why certain types of map projections are better than others for different purposes. Yet just by the name “equidistant” it gave me the wrong idea that the distances between random points would somehow be conserved; the idea which soon became clear to me that it was not feasible. This exercise clearly demonstrated the dangers that one might face if one is not careful with the use of the maps.