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Re: Geographic Lat/Lon [message #59895 is a reply to message #59894]

Fri, 11 April 2008 14:59

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

robinson.inj@gmail.com writes:

> I was wondering if someone could suggest me how to specify the
> following ENVI information in IDL:
>
> map info = {Geographic Lat/Lon, 1.0000, 1.0000, -130.54072891,
> 40.00000000, 4.8112599312e-003, 4.8112599312e-003, WGS-84,
> units=Degrees}
>
> I need to create lats and lons grids for the "Geographic Lat/Lon"
> projection and they must give me the same geolocation for each pixel
> as ENVI does. I am using IDL 6.3

I am WAY out on a limb here (too many margaritas, probably),
but I'm going to guess that this structure tells you that
the "tie-point" associated with the (1,1) pixel (upper-left
pixel in ENVI, I guess) is at (-130.540, 40) in lon/lat,
and that each pixel is scaled at 4.811e-3 in X and Y.
So, starting at the tie point, each pixel has a longitude
of :

lons = -130.540 * Indgen(ysize) * 4.811e-3
lats = 40.00 * Indgen(xsize) * 4.811e-3

You can make arrays of the appropriate size by matrix
multiplication. Units are in degrees, I would guess.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: Geographic Lat/Lon By: jeffnettles4870 on Sat, 12 April 2008 15:45
		Re: Geographic Lat/Lon By: David Fanning on Fri, 11 April 2008 16:33
		Re: Geographic Lat/Lon By: robinson.inj on Fri, 11 April 2008 15:33
		Re: Geographic Lat/Lon By: David Fanning on Fri, 11 April 2008 15:00
		Re: Geographic Lat/Lon By: David Fanning on Fri, 11 April 2008 14:59
		Re: Geographic Lat/Lon By: Jean H. on Fri, 11 April 2008 14:39
		Re: Geographic Lat/Lon By: robinson.inj on Fri, 11 April 2008 14:20
		Re: Geographic Lat/Lon By: d.poreh on Fri, 11 April 2008 11:13

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