I always heard it was a plot developed by a couple of real estate representatives in Greenland
I could be wrong (I have been wrong twice before) but isn’t the Peters Projection just an orthographic projection with the equator as the circle of tangency? I would love any of the cartographic types to fill me in on this.
I remember seeing this sort of projection for the first time a ways back and liked the equal area nature of it. For one thing it explained, despite their ideological alignment, the Soviet Union’s preoccupation with China.
And dontcha just love words like loxodrome and rhumb line. I think the latter’s the course that most pirates steered…Arrrrr. 
The Mercator projection is still a useful map for navigating. If you connect two points on the map with a straight line, you can get a bearing to sail from point A to point B easily. This is a rhumb line, and for short distances is not noticeably longer than a great circle arc. Pirates, and all navigators prior to the invention of the chronograph, pretty much had to sail rhumb lines. This is because they could only determine their latitude (with a sextant), and not their longitude. After the chronograph was invented, it became possible to sail arcs of great circles.
The Mercator projection was still useful for plotting courses over short distances, but useless for plotting a great circle course. To plot a great circle course, the gnomonic projection was used. With this type of map, a great circle course appears as a straight line. Several coordinates along the course were then transferred to a Mercator map, and the short segments connected with rhumb lines. I believe the same basic idea is still used.
The Mercator spreads out countries most North (but curiously, not South), but does it condense countries near the equator?
What’s the principle behind it?
[QUOTE]
*Originally posted by Pashnish Ewing *
The image used in the West Wing episode was the Peters projection
QUOTE]
Doh!
All right. The last line, in parens, is “I have to ask: what’s wrong with a globe?” – Wing Chun
The Peters map is unsatisfactory–just compare it to a globe, and other equal area maps.
It spreads out equally on the north and south. Occasionally you see Mercator projection maps where Antarctica is just huge. Usually they just cut most of it off. It just so happens that the other stuff in the southern hemisphere is closer to the equator than the stuff in the northern hemisphere.
The way it’s made is to wrap a sheet of paper around the earth, touching it at the equator. Then project everything out from the center of the earth onto the paper, and unroll the sheet.
Three’s a charm. Such an orthographic projection would actually reduce the relative size of Greenland. The Peters is an equal area projection. Here’s a decent link (although they call it "orto"graphic) to a list of map projections. It mentions that the Peters is a square map, that is also equal-area, but Lambert’s Cylindrical Equal Area has been around a lot longer. If you look at a Peters map, Africa appears to be about twice as tall as it is wide, whereas those dimensions are about the same in reality.
I think if it were that simple, it would have been called the Ptolemy. An actual Mercator map is a non-projection, using a mathematical formula to space the latitude lines, and that formula is not equivalent to projection from the center of the earth. Still, you can find web resources that do it exactly that way–USGS Teachers Lesson, for example, but note their caveat: “This map approximates the characteristics of the Mercator projection within about 2 percent.”
RM Mentock - you put an empty URL in your link, so it just links back to the SDMB.
Mercator projection - it’s done by formula now, and requires a bit of calculus to derive the formula. Mercator lived before calculus, and did by meticulously plotting very small latitude increments and measuring. The formula, and some background may be found here:
If you want to read a really interesting account of the Peter’s projection controversy (it shouldn’t really even be called the Peter’s projection since he essentially ripped off an earlier map) try:
“Drawing the Line” by Mark Monmonier. The whole book is really interesting, (I read it for a class on cartographic ethics) but they do have a chapter on map projections.
Yikes, just saw this. I got it again by googling on +“USGS”+"“teachers lesson”+“Mercator” : USGS Teachers Lesson.
Any good Outback restaurant with all its paraphenalia will have a copy of that map mounted on the wall behind the hostess stand.