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Re: GridData Conundrum [message #70564 is a reply to message #70476]

Mon, 19 April 2010 07:03

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Klemen writes:

> Hi David, I have no problems with GRIDDATA; take a look at the code.
> The only problem I had was the triangulate function - you might have
> problems with collinear points on the poles if you don't remove
> them).

Ah, ha! Thanks, Klemen.

This is similar to what I had originally done, but I couldn't
overcome that darn collinear points problem. Eventually, I made
triangles from the original data XY and that "worked", so I thought
that must be right. It never occurred to me that the pole points
could be the problem.

Just one correction to your code. You set up a polar
stereographic map projection like this:

map=map_proj_init(106, DATUM=8, /GCTP, center_lon=-45., center_lat=90.)

This is incorrect. In the polar stereographic projection (only!!)
the CENTER_LAT keyword is actually the TRUE_SCALE_LATITUDE
keyword. (This is being fixed, thank goodness, in IDL 8.0, since
*everyone* makes this mistake.)

http://www.dfanning.com/map_tips/polarstereo.html

The projection should really be set up like this:

map=map_proj_init(106, DATUM=8, /GCTP, center_lon=-45., center_lat=70.)

I'm really grateful for your help. :-)

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]

		GridData Conundrum By: David Fanning on Sat, 17 April 2010 10:19
		Re: GridData Conundrum By: David Fanning on Mon, 19 April 2010 13:46
		Re: GridData Conundrum By: David Fanning on Wed, 21 April 2010 12:23
		Re: GridData Conundrum By: David Fanning on Mon, 19 April 2010 11:52
		Re: GridData Conundrum By: Klemen on Mon, 19 April 2010 07:44
		Re: GridData Conundrum By: David Fanning on Mon, 19 April 2010 07:03
		Re: GridData Conundrum By: David Fanning on Thu, 22 April 2010 06:07
		Re: GridData Conundrum By: ben.bighair on Thu, 22 April 2010 05:35

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