Lab 5 (week 6)

(click the image for a larger view)

To answer the perhaps rhetorical questions in the lab guide: The equator spans about 24,948 miles. The Northern and Southern-most graticule lines also span about 24,948 miles, but they represent the North and South poles (single points).
Alaska and Greenland are not really bigger than Brazil. Their areas are distorted by the Mercator projection, since the Mercator projection is a conformal projection which preserves shape and direction. The distance between Washington, D.C. and Kabul with the Mercator projection is about 10,093 miles.

Why Map Projections are Important:

Map projections are important for several reasons. They distort the world’s surface, and can significantly change distance, area, and direction. This is especially relevant when taking measurements for scientific studies or other projects. Map projections are a convenience because they make geographic data easier to work with, in spite of distorting it. Map projections can even affect the way we perceive the world.

Perhaps the most obvious significance of map projections is how they distort the Earth. In order for the three dimensional, spherical surface of the earth to be converted to the two dimensional, flat surface of a map, either distance, area, or shape (or all three, to varying extents) must be compromised. The six map projections shown above are a good example of different types of compromises. The measured distance from Washington, D.C. is significantly inaccurate in all of the projections except for the equidistant ones, which were specifically created to preserve distances. Other types of distortion are obvious, such as the enormous size of Antarctica in the Mercator projection, and the warped angles in the Bonne projection. Scientists must take care to select a map projection which preserves features most critical to their study interest.

So, why use map projections at all if they cause distortions? The reasons were more pertinent in past times. The only practical way to represent the Earth was on paper, a flat medium. Projections were necessary to translate the Earth onto a plane which is much easier to work with. Three dimensional globes are an option, but they have several drawbacks: they are costly to make, difficult to transport and work with, and unless you use immense resources to make a giant globe, their scale is rather limited. Now, with computers, storage of three dimensional data is possible, but takes more memory, software, and computing power. Also, while two dimensional data can be printed onto a page, there is currently no easy way to transfer three dimensional data from a computer into the real world.

From personal experience, I would argue that map projections have the ability to alter how humans perceive the Earth. For example, the map projections I am most used to seeing is the Robinson map projection. I remember being confused the first time I saw a polar stereographic projection of Antarctica, showing it accurately as a rather small, round land-mass. In the Robinson projection, Antarctica is enlarged and stretched out so that it looks like a very long continent. In fact, nobody seems to care about Antarctica, since it is almost always grossly distorted in map projections (it is infinitely large in the Mercator projection, and stretched all the way around 360° of the map in the Equidistant Conic and Behrmann projections). Also, because of how the Robinson map projection is centered at the Prime Meridian, I used to forget that Alaska was so close to Asia. I believe it perplexed me the first time I heard about the theoretical former ice bridge between the two continents, since they seemed so far away. Fortunately, my misconceptions were easily corrected at a young age. However, it takes looking at several different map projections, or a globe, to gain an accurate understanding of the Earth’s structure.