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I am creating a map showing flight paths originating in the United States and traveling to Asia and Europe. I need a projection for the world that will focus the United States in the center of the map, with Asia showing up to the west and Europe to the east. Does anyone know where I might find a projection like this?

Edit: I am working in ArcInfo 10.

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4 Answers 4

up vote 14 down vote accepted

I don't know of a predefined one but you should be able to take any good global projection (for some value of good) and change the central meridian to be one running through the US instead of through Greenwich.

You will need to post more details of the system you are using before we can give detailed instructions on how to create a custom projection.

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Second this. Any projection is fine, as long as the central meridian is set to somewhere in the middle of the US. –  Jason Scheirer Jan 4 '11 at 22:00
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@Jason Did you really mean any projection?? It's difficult to find one that works well over such an area. –  whuber Jan 5 '11 at 2:25
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Might have been a slight exaggeration. –  Jason Scheirer Jan 5 '11 at 5:03

Because the sphere is not homeomorphic to the plane, something's gotta give. The trick is to place the bad point (or points) of the projection at places of little interest. If you're focusing on Europe and Asia and routes between, you want to cover all of the northern hemisphere, including around the pole, and maybe some parts of the southern hemisphere. If you don't want to break your projection--and breaking will visually interrupt representations of routes--then consider an azimuthal equidistant projection centered at some point within or near North America. If you want a conformal projection, so that angles are locally preserved, you should look at some aspect of the stereographic projection. (The usual polar stereographic projection might do the job nicely, without modification.) Both of these can project the entire world (minus one point), but of course both of them introduce fairly grievous distortions at locations near the missing point. They both do fine for a hemisphere and a little bit more.

If you must have Asia to the left and Europe to the right, you are almost forced to break the projection in mid-Asia. Many of the conic and polyconic projections will do a good job of this. For an example that places North America in the middle, see this image.

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Google, bing, and esri all use a mercator, projected> world> web mercator auxiliary sphere.

wkid 102100

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Mercator is good for loxodromes (rhumb lines), but in the 21st century those are irrelevant to navigation. The singularities of the Mercator at two points, and the attendant huge distortions there, do not recommend it for this application. –  whuber Jan 5 '11 at 2:13

Gnomonic Projection - is used for shortest routes between points on a globe

alt text

http://en.wikipedia.org/wiki/Gnomonic_projection

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The gnomonic projection is not a world projection. It projects less than a hemisphere; the great circle bounding that hemisphere is at infinity in the projected plane. –  whuber Jan 5 '11 at 2:11

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