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Re: map projection question [message #31391 is a reply to message #31389]

Tue, 09 July 2002 12:35

James Kuyper
Messages: 425
Registered: March 2000

Senior Member

"J. Li" wrote:
>
> Hi,
>
> I have a small strip of satellite image, centered around the
> International Date Line +/-5, i.e the longitudes range from -175 to 175.
>
> How do I limit the MAP_SET to the smaller portion of the Earth, say -175
> LON -> dateline -> +175 LON instead of the larger -175 LON -> Prime
> Meridian -> +175 LON? I cannot find a keyword that will let me to choose
> which portion to map. LIMIT keyword alone seems to be insufficient.

The limit keyword is sufficient. Compare:

This one covers 175 -> 180 -> -180 -> -175:
map_set, 0, 180, /hires, limit=[60, 175, 70, -175], /isotropic

This one covers -175 -> 0 -> 175:
map_set, 0, 0, /continents, limit=[-60, -175, 70, 175], /isotropic

The key things are the change in the center longitude, and in the
positions of the 175 and the -175, the other differences are purely
cosmetic. I chose 'isotropic' to keep the coastline shapes recognizable.
Since the first plot is much narrower than the second, I chose to make
it much shorter from north to south as well. The larger plot doesn't
need /hires, but the smaller one looks much better with it.

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[Message index]

		Re: map projection question By: Mark Hadfield on Tue, 09 July 2002 15:08
		Re: map projection question By: Robert Stockwell on Tue, 09 July 2002 14:54
		Re: map projection question By: James Kuyper on Tue, 09 July 2002 12:35
		Re: map projection question By: Liam E. Gumley on Tue, 09 July 2002 11:48

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