Editing 2911: Greenland Size
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==Explanation== | ==Explanation== | ||
− | {{ | + | {{incomplete|Created by a GREEN LAND FOR ANTS - Please change this comment when editing this page. Do NOT delete this tag too soon.}} |
− | + | Because the {{w|Earth}} is curved, all flat maps have some distortion. (A common comparison is flattening an orange peel, which cannot be done without tearing and wrinkling it.) Different {{w|map projection}}s can distort different {{w|Map projection#Metric properties of maps|metric properties}}, such as distances, areas, and angles, while leaving others intact. It can be desirable to preserve different metrics in different applications. | |
− | + | The {{w|Mercator projection}}, depicted in the comic, prioritizes depicting correct angles. This allows for easy course planning at sea, and makes shapes fairly accurate. In exchange, Mercator is often criticized for distorting size: distances near the poles look larger than the same distance near the {{w|equator}}. A common complaint is that {{w|Greenland}} appears as big on the map as {{w|Africa}}, when Africa actually has 14 times as much area as Greenland. When these size distortions are presented out of context, they can create bias and misconceptions about different places. | |
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− | + | [[Cueball]]'s dialogue leads the reader to expect this complaint. However, instead of comparing ''relative'' sizes of two landmasses within the map, [[Cueball]] compares the ''absolute'' sizes of the depiction of Greenland and the actual Greenland. On a typical world map, Greenland might be centimeters or inches across. Judging from the human characters, the mapped Greenland in this comic might be 10 cm across. In real life, Greenland is about 650 miles or 1,050 km across from east to west ([//britannica.com/place/Greenland source]). Cueball deems this difference misleading, presenting it as a failure of this specific map or projection. | |
− | + | Of course, this is absurd. The purpose of any map is to present information much more compactly so that it is easy to read and interpret. Any actual-size world map would have to be the size of the Earth's surface, in which case it would have few uses. In addition, if a map includes a {{w|Scale (map)|scale}}, it enables the user to use the ratio to calculate the actual size of the places depicted (though this would not be possible on a Mercator projection, since the map-to-reality scale is not constant). | |
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− | + | The title text is about the fact that a horizontal line on a worldwide Mercator projection corresponds to a line of latitude. Most lines of latitude are thousands of miles (kilometers) long, but they become smaller and smaller approaching the poles, and in fact there ''is'' a line of latitude in a small-diameter circle around each pole whose length would equal the width of the map that Cueball is looking at. If Cueball's map were 1 m wide, then this line of latitude would be at 89.999998568° N or S - that is, the line of latitude there would be a circle with a circumference of 1 m around each of the poles. | |
− | + | A map at a scale of 1:1 was discussed in {{w|Lewis Carroll}}'s "{{w|Sylvie and Bruno Concluded}}": | |
− | + | <blockquote> | |
+ | ''"What a useful thing a pocket-map is!" I remarked.''<br> | ||
+ | ''"That's another thing we've learned from ''your'' Nation," said Mein Herr, "map-making. But we've carried it much further than ''you''. What do you consider the ''largest'' map that would be really useful?"''<br> | ||
+ | ''"About six inches to the mile."''<br> | ||
+ | ''"Only ''six inches''!" exclaimed Mein Herr. "We very soon got to six ''yards'' to the mile. Then we tried a ''hundred'' yards to the mile. And then came the grandest idea of all! We actually made a map of the country, on the scale of ''a mile to the mile''!"''<br> | ||
+ | ''"Have you used it much?" I enquired.''<br> | ||
+ | ''"It has never been spread out, yet," said Mein Herr: "the farmers objected: they said it would cover the whole country, and shut out the sunlight! So we now use the country itself, as its own map, and I assure you it does nearly as well."'' | ||
+ | </blockquote> | ||
− | The idea | + | The same idea was expanded in {{w|Jorge Luis Borges}}'s "{{w|On Exactitude in Science}}". |
− | Mercator projections have been mentioned previously in [[977: Map Projections]], [[2082: Mercator Projection]], and [[2613: Bad Map Projection: Madagascator | + | Mercator projections have been mentioned previously in [[977: Map Projections]], [[2082: Mercator Projection]], and [[2613: Bad Map Projection: Madagascator]]. |
==Transcript== | ==Transcript== |