LAB 5

MAP PROJECTIONS 

Significance, Perils, & Potentials 

of Map Projections 

       Map projections are important because they are a way to translate the three dimensional world onto a two dimensional surface. However, because it is impossible to retain all the three dimensional aspects, it is important to know which projection is best for the information you are trying to convey. All maps have some distortion, but different projections maintain specific aspects of the three dimensional world. These three projections include conformal, equal-area, and equidistant.

        Conformal maps preserve angles. So if two curves intersect at a specific angle, the images of the two curves on the map also intersect at the same angle. The Mercator map projection was  the standard map for nautical purpose because of its ability to represent lines of constant course as straight segments. This map preserves angles and small shapes because the linear scale remains constant. It does come with obvious distortions of the size and shape of large objects as the scale increases from the equator to the poles (note that Greenland is larger than the US). The stereographic projection also preserves angles, but neither area or distance. Like the Mercator map it creates more distortions towards the poles, but does not look as extreme (compare Antarctica and Greenland between both).

        A second type of map projection is one that maintains equal area such as the Bonne and cylindrical equal-area projections. The Bonne projection is pseudoconical with all parallels being concentric arcs of circle, all equally spaced and all standard lines. Scale is correct along the straight vertical central meridian. However, deformaties increase towards the edges of the map. The cylindrical equal-area projection is quite a contrast with the Bonne projection, but it does conserve area. It has straight parallels and meridians. The projection stretches the continents east to west and distortions also increase towards the poles.

       The third category of map projections is equidistant maps that preserve distance from one standard point or line. With the equidistant conic projection the scale is the same along all meridians because it has constant parallel spacing. It is not equal area or conformal and obviously distorts the south pole. With sinusoidal map projections, distances along parallels are preserved. It shows relative sizes fairly accurately but distorts shapes and directions. There is no distortion along the central meridian or equator.

        I have given examples of the different categories of map projections as well as specific examples for each category. Even though two maps may try to preserve the same thing, there are still discrepancies in distances as noted by the variable measurements from Washington DC to Kabul. Also, I have only provide two examples of each type of projection but in reality there are a plethora that can be found that falls under the three categories and there are even some that do not fall under any, such as the popular Robinson map projection. Note that although some projections may preserve more than one thing, it is impossible to preserve all. Nevertheless, it is important to understand the different projections and what they conserve to appropriately convey a certain set of information. These projections have been used for many years and will continually be used for many more to come because they are so integral in understanding distances, angles, and areas of places around the world. 

Examples