Week 6 Lab 5

 

This week in lab we looked at the differences in distance between Washington DC and Kabul, Afghanistan, depending on what map projection we used. We had to do six projections – two for each type (conform, equidistant, and equal area). It was pretty surprising how drastic the differences in distance were between projections. When I think about distance, I think that it is a unique number – if we can measure it, then it’s always the same, right? WRONG. At least in terms of global map projections, distance gets distorted in a certain way.

From this exercise the significance of map projections are pretty obvious. They are absolutely necessary based on the very nature of what a map is. The world is a sphere-like orb, and paper is two-dimensional. Therefore it is the eternal problem of the map-maker to figure out how to display a 3D thing onto paper. Obviously, people have disagreed about the best ways to do so, and thus, the many projections we have.

Conformal map projections preserve angles locally. Aside from geography, conformal maps are used greatly in physics and engineering, as their angle-preserving nature lends itself to many math problems and equations (for example, the Mercator map was created as a navigational tool, whereby the commonly traveled routes appeared as straight lines). Equidistant maps preserve distance from some standard point or line, ie the equator or the prime meridian, or both. If both, it is called an equirectangular projection, which is what the Plate Carrée model is. Finally, an equal-area projection is one in which every grid section has the same area.

All of these maps have different implications and uses. For example, while the Mercator map was probably useful to the sailors that invented it hundreds of years ago, today its distortions are very misleading to our general worldview. Because of the way each map type displays the world, they might be used by different special interests. Again with the Mercator, the Northern Hemisphere has kept it in widespread use in schools for so long, because it makes North America and Europe look way bigger in proportion to South America and Africa than they should. Thus the “importance” of each hemisphere is skewed.

We have to be really careful when deciding which projection to use, because though most of them distort one or more aspects of the world, it is a very subtle distortion. None of them, even the Mercator, are wrong, they are just displaying information in different ways. Most Americans, myself included until a few years ago, don’t know how skewed their perception of the world is, and so I think that it is extremely important for schools and other institutions to use as accurate a projection as possible (cartographers say these are square-grid, and not rectangular-grid projections).