Interpol. irregular grid to irregular grid

Interpol. irregular grid to irregular grid

Post by deja_j.. » Wed, 07 Feb 2001 11:23:21



howdy!

i'm trying to interpolate data from one irregular
2-D grid to another (different) irregular 2-D
grid:

- does IDL have any other built-in functions
besides MIN_CURVE_SURF that can do this?
- does anyone have any warnings regarding the
behavior of MIN_CURVE_SURF?
- has anyone implemented irregular-to-irregular
interpolations using other algorithms?

thanks!

best,
-Johnny Lin

-------------------------------------------
Johnny Lin
CIRES, University of Colorado
Work Phone:  (303) 735-1636
Web:  http://cires.colorado.edu/~johnny/
-------------------------------------------

Sent via Deja.com
http://www.deja.com/

 
 
 

Interpol. irregular grid to irregular grid

Post by Mark Hadfiel » Sat, 10 Feb 2001 05:32:40



> howdy!

> i'm trying to interpolate data from one irregular
> 2-D grid to another (different) irregular 2-D
> grid:

> - does IDL have any other built-in functions
> besides MIN_CURVE_SURF that can do this?

Not that I'm aware of. It's a pity because there's no fundamental reason why
TRIGRID (for example) couldn't be modified to handled irregular output
grids.

Quote:> - does anyone have any warnings regarding the
> behavior of MIN_CURVE_SURF?

Yes! It's terribly slow when the input grid is of a significant size. For an
NxN input grid, the execution time of MIN_CURVE_SURF increases as approx.
N^3. This is because the alogorithm is non-local, i.e. every point in the
input grid affects every point in the output grid.

Quote:> - has anyone implemented irregular-to-irregular
> interpolations using other algorithms?

No but you could try calling TRIGRID repeatedly, once for every output
point...

---
Mark Hadfield

National Institute for Water and Atmospheric Research

 
 
 

Interpol. irregular grid to irregular grid

Post by deja_j.. » Sat, 10 Feb 2001 09:51:59


Craig and Mark,

thanks for your help!  the grid turns out to be too large for
MIN_CURVE_SURF to be efficient, and the presence of missing
values in the dataset made MIN_CURVE_SURF troublesome, so i
ended up coding a near-neighbor scheme.

thanks again!

best,
-Johnny

-------------------------------------------
Johnny Lin
CIRES, University of Colorado
Work Phone:  (303) 735-1636
-------------------------------------------

Sent via Deja.com
http://www.deja.com/

 
 
 

1. Interpolation from a regular to an irregular grid?

Hi, I am kind of new to IDL, and have just started a new job in
physical oceanography in Portugal.  At present I am familiarising
myself with IDL, which I will be using extensively.

One of my first tasks is to find a way to input satellite collected
wind data into an ocean model that is being run here.  The wind data
are regularly spaced, whereas the model requires the data in a series
of irregularly spaced intervals.

Looking through the messages on this group I see many questions and
answers about working from irregular to regular grids using
Triangulate and Trigrid, but I wonder if anyone knows how to do the
reverse?

Thanks

Evan Mason

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