| Re: map projection question [message #31386] |
Tue, 09 July 2002 15:08 |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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"Robert Stockwell" <rgs1967@hotmail.com> wrote in message
news:3D2B5BB2.9030903@hotmail.com...
> map_set, 0, -180, limit=[-40,175,40,-175], /cont, /grid,label=1,hires=1
>
> ...
>
> PS that's a nice stretch of ocean!
Indeed, one of my favourites. But there is some nice land in it, too
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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| Re: map projection question [message #31389 is a reply to message #31386] |
Tue, 09 July 2002 14:54  |
Robert Stockwell
Messages: 74
Registered: October 2001
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Member |
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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.
>
> thanks very much in advance
>
> JYL
map_set, 0, -180, limit=[-40,175,40,-175], /cont, /grid,label=1,hires=1
note the order of the 175 and the -175
cheers,
bob
PS that's a nice stretch of ocean!
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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
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Senior Member |
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"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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| Re: map projection question [message #31392 is a reply to message #31391] |
Tue, 09 July 2002 11:48 |
Liam E. Gumley
Messages: 378
Registered: January 2000
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Senior Member |
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"J. Li" wrote:
> 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.
How about something like this?
window, /free, xsize=200, ysize=800
map_set, 0, -180, scale=50e6, /cont, /grid
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
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