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Re: weird behavior of Triangulate [message #81273 is a reply to message #81272]

Sat, 01 September 2012 18:10

envi35@yahoo.ca
Messages: 48
Registered: March 2005

Member

On Sep 1, 10:45 am, David Fanning <n...@idlcoyote.com> wrote:
> Jenny writes:
>> Hi David, I was actually following your example of GRIDDATA:http://
>> www.idlcoyote.com/code_tips/usegriddata.html
>> My data is similar as your NCEP data used in your example, except they
>> are on 0.5 and 0.75 lat/lon degree (unprojected). I should have said
>> they are irregular! Any ideas why Triangulate works on the first set
>> but not the second?
>
> Yes, but did you read that article through to its conclusion?
> If you did, you might agree with me that GridData is a
> bit of a dog's dish.
>
> Every four or five months I get the idea that I ought
> to be able to use GridData to regrid data. I convince
> myself that I know what I am doing, and I start in on
> it. The article you cite was the only time in 5-6 attempts
> that I've even come close to being successful. And, then
> only because I used a small data set.
>
> In my latest attempt, several weeks ago, I used a LandSat
> image band and tried to regrid it to a UTM grid. I started
> the program on a Friday night and just decided to let it run
> until it was finished. I gave up on it sometime Sunday morning
> and killed IDL. I can't really recommend this as a real-time
> solution. :-)
>
> My conclusion is that if you need things regridded (and
> if you work with satellite images, this is *always*
> required, eventually), you will have to use something other
> than IDL to do the job.

David, thanks for sharing. I did compared results from GRIDDATA and
those from a Fortran code (both using inverse-distance method)for my
first set of data, and they look identical. So seems GRIDDATA work ok
for small datasets. However, I agree that for large datasets, such as
Landsat, other languages (i.e Fortran, C) are much more efficient. I
don't understand why we shouldn't have confidence in results from
GRIDDATA? and why it doesn't always work?!

Jenny

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[Message index]

		Re: weird behavior of Triangulate By: David Fanning on Sat, 01 September 2012 18:26
		Re: weird behavior of Triangulate By: envi35@yahoo.ca on Sat, 01 September 2012 18:10
		Re: weird behavior of Triangulate By: David Fanning on Sat, 01 September 2012 07:45
		Re: weird behavior of Triangulate By: envi35@yahoo.ca on Sat, 01 September 2012 07:17
		Re: weird behavior of Triangulate By: David Fanning on Sat, 01 September 2012 06:59
		Re: weird behavior of Triangulate By: Yngvar Larsen on Thu, 06 September 2012 07:06

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