| I'm doing something wrong with map_image [message #76381] |
Tue, 31 May 2011 14:01  |
almost_like_a_metapho
Messages: 8
Registered: May 2011
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Junior Member |
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Direct graphics.
I have a map image in cylindrical projection (so basically the sides
of my map are lat-90 to 90 and lon -180 to 180), so I'm using map_set
with /cylindrical. The image, is around 3000x1500 pixels
I want to plot data on a small 3x3 degree slice of this map, say
centered on lat=10, lon=10. I can set my map_set properly, but my
map_image does not seem to be doing what I want it to. I want to get
that 3x3 slice of the image displayed, place my map_grid over it, then
plot my points, and I can't.
It's got to be a gloriously simple thing that I'm missing.
N
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| Re: I'm doing something wrong with map_image [message #76448 is a reply to message #76381] |
Wed, 01 June 2011 17:06  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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almost_like_a_metaphor writes:
> At some point I'm going to have to figure out if I can read in a small
> portion of a large image, to save on i/o. Assoc might do it, if I
> understand assoc correctly. (e.g. a 36000 x 18000 cylindrical
> projection image (with .01 degrees per pixel, of which I'd like to
> read in only a 2x2 degree square).
Well, possibly, but I doubt ASSOC is going to be
much good for all the skipping around you will
have to do in the file. It would be better
to put the image in a format like netCDF, where
tools for reading a portion of a 2D data array
already exist and you don't have to roll your own.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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