Lab #5 Map Projections

Equal area map projections preserve area. Both the Eckert IV and Mollweide projections are pseudocylindrical. 

Conformal map projections preserve angles on a map. The most common conformal projection is the mercator projection. The Hotine projection, also known as the Hotine oblique mercator projection, is a cylindrical projection. The Azimuthal stereographic map projection is also conformal.

Equidistant maps preserve distance. The polyclinic, or American polyconic, projection is equidistant and projected using a cone shape. The Berghaus star projection is equidistant in the northern hemisphere and is based on the Azimuthal equidistant projection.

Map projection is a very important part of geography. We live in a three dimensional world, but we look at two dimensional maps most of the time. In order to translate the three dimensional globe onto a two dimensional map, a projection needs to be chosen that will suit the map’s purpose. By projecting a map, some aspects of the map will be distorted. Different map projections will distort different parts of the map. For example, conformal maps will distort distance and area, but preserve area; equidistant maps will distort area and angles, but preserve distance; and equal area maps will distort distance and angles, but preserve area.


Different map projections are useful in different cases. For example, conformal maps are useful while navigating. Though they distort distance and area, angles are preserve, which is the most important part of navigating. The most common conformal map is the mercator projection, which is often used in navigation. If the map's purpose is to compare the distance between points, equidistant projections will be the most useful. Even though area and angles are distorted, distance is the only important aspect of the map in this case. In many map projections, the size of different areas are distorted. For example, Greenland is often huge, while Africa is relatively small. If the purpose of the map is to compare sizes of continents, countries, or other areas, equal area maps are the most useful. These three map projections are useful for different purposes.


Knowing how map projections work is very important when looking at a map. Depending on the map you are looking at, it is important to realize that some aspects will always be distorted. For example, in a conformal map projection, it is important to realize the sizes of areas are more and more distorted the further away from the equator you get (assuming you are looking at a mercator projection.) Distance is a key aspect of maps that will be distorted. Looking at the measured distances between Washington DC and Kabul, you see discrepancies between the projections. Though some of the projections measure distance relatively accurately, they still variate, especially when looking at a conformal map.


Other differences to note between projections is that some projections cannot use a North arrow. For example, if the north pole is located in the middle of the projection, as opposed to the edge, a North arrow cannot be used. Also, the scale bar becomes irrelevant when looking at certain projections. Usually, equidistant maps are able to use scale bars. Also, some conformal and equal area maps can use them to an extent. However, some map projections distort distance so much that it becomes very unreliable to use a scale bar to measure distance.