Lab 5: Map Projections

Map projection is the process of converting a spherical model onto a planar model, while keeping specific spatial characteristics, such as distance, area, or shape. This process essentially enables the creation of accurate flat maps. We must be aware that not one projection type can accurately depict all of the characteristics displayed originally on a sphere to the plane. Hence we will have different projection types: namely conformal, equidistant, and equal area. Each of these types are used in different situations and provide different benefits when applied to these. Everyone of these types allow the possibility of depicting a spherical 3-D world (globe) on a 2-D projection, creating possibilities such as easier transportation of a peice of paper over a globe.

The first type, conformal map projections, keep the shape shape and local angles, depicting a system of longitude and latitude lines. Conformal maps distort area, which is made obvious by the disproportionate size of Antarctica in both Mercator and Gall stereographic examples. Equidistant map projections, such as cylindrical and conic above, represent accurate distances along designated lines and outward from the center. The disadvantage is that this type of projection distorts area sizes, and does not necessarily show true distances of the points along the center, as we can see in the inaccurate distance between the Americas and Australia in the equidistant conic example. Equal area map projections preserve areas but fail to accurately represent latitude-longitude grid angles. Cylindrical, also known as a Gall-Peters projection, only represent true distances along the 45th parallels north and south. On the other hand, sinusoidal represents the area of the Earth as the area between two symmetrically rotated cosine curves. We can clearly see in both cylindrical and sinusoidal equal area examples that these gridlines are distorted, simply by comparing both to the conformal Mercator example.

In this lab we were to measure the distance between Washington, D.C. and Kabul. Here we can see the differences between the types of map projections. To determine bearing we can look at both Mercator and Gall Stereographic conformal map projections. We see that the linearity in all directions dictates that traveling southeast in a straight line will conveniently get me from D.C. to Kabul. To determine true distance we can look at both cylindrical and conic equidistant map projections. We see that the even mapping of longitudes and latitudes dictates that the true distance between D.C. and Kabul is around 5,065 to 6,941 miles. And as obvious as its name says, we can accurately assess the areas of the United States and Afghanistan by referring to both cylindrical and sinusoidal equal area projections. I am certain that interchanging any of these projection types with the data we are seeking, will only result in false measurements.

In all of these map projection types we have have pros and cons when depicting the world on a 2-D scale. Since it is obviously impossible to accurately translate all spatial data from a sphere to a plane, each projection will preserve some characteristics while significantly distorting the rest. As mentioned before each map projection has its proper use, which is why any spatial analysis can be rendered erroneous if the wrong type of projection is chosen. It is important to know through what means each map was created because then you will accurately know the features that it most accurately represents while at the same time lacks.