Lecture 4 - Map Projection
In the last lecture we learned there are two ways to represent locations on maps: with a
Geographic Coordinate System (latitude, longitude) and a Projected Coordinate System (x,
y). This lecture will focus on the latter, starting with map projections.
Table of Contents
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1. What is a Map Projection?
2. Are these good maps?
3. Categories of Map Projections?
4. What makes a projection good?
1. What is a Map Projection?
A
map projection
is a mathematical process of displaying a particular region of the earth's
three-dimensional curved surface onto a two-dimensional flat map. A good globe can
provide the most accurate representation of the Earth. However a globe isn't practical for
many of the functions served by a map. It's not convenient to carry a globe during hiking,
where you'd prefer to look at a piece of paper or a digital map. Map projections allow us to
represent some of, or the Earth’s entire surface, on a flat easily transportable surface, such
as a sheet of paper.
Figure 1. Map Projection - the transformation of a curved earth to a flat
map
In the translation from a three-dimensional spherical surface to a two-dimensional flat
surface, you also change how you express location. In the real spherical world, locations are
described using two angles (i.e., Latitude & Longitude). In the flattened map of virtual world,
positions are typically described in Cartesian Coordinates X & Y with a unit of length, such
as the meter.
The process of translating information from the spherical Earth onto a map causes every
projection to distort at least one aspect of the real world – shape, area, distance, or direction.
2. Are these good maps?
The strengths of this projection are also its weaknesses. From a cartography standpoint, it gets many things wrong: ●It is Eurocentric, and it places the northern hemisphere on top, encouraging thinking of the northern hemisphere as dominant. ●It distorts the polar regions, including the northern parts of the globe (giving a false sense of size to small northern countries). The best example of the distortion can be seen in Greenland. On this map Greenland looks larger than South America, while as a matter of fact, it is closer in size to Mexico. Also while Africa is about 14 times larger than Greenland, on this projection the two appear to be the same size. These are the most common criticisms leveled at the map. There are probably more, and not everyone would accept all of them as valid. But that’s not the point here. How about the map in Figure 3? Is it a good map? What is unusual about this map compared to other world maps you have seen? Figure 3. Who says North has to be on top? Different perspective: McArthur’s world mapMcArthur's Universal Corrective Map of the World has a fabulous history: it was made by an Australian who was tormented for coming from the "bottom of the world." It was the first modern south-up map, published in 1979. This map has a unique viewpoint with cheeky Aussie humor. Its maker, Stuart McArthur, drew his first South-Up map when he was 12 years old. His geography teacher told him to re-do his assignment with the “correct” way up if he wanted to pass. Three years later he was an exchange student in Japan. He was teased by his exchange student friends from the U.S. for coming from “the bottom of the world.” It was then, at age 15, he resolved to one day publish a map with Australia at the top. Six years later while at Melbourne University, he produced the world‘s first “modern”
south-up map and launched it on Australia day in 1979. It has sold over 350,000 copies to
