Re: fitgrid algorithm

On Aug 21, 2006, at 5:01 PM, Sanjoy Som wrote:

> Hello ncarg community,
>
> I was wondering if anyone knew whether the fitgrid interpolation
> algorithm in ncarg is the same as the minimum-curvature algorithm
> found in GMT?

All algorithms in fitgrid are based on the work of Alan
Cline and comprise a subset of Cline's Fitpack package.
A significant part of Fitpack is available from netlib:

   http://www.netlib.org/fitpack/

The algorithms are described in:

   A. K. Cline, Scalar- and planar-valued curve fitting using splines
   under tension, Communications of the ACM, v.17 n.4, p.218-220,
   April 1974

and are founded on splines under tension.

I am not familiar with the the minimum curvature algorithm used
in GMT, but in looking at:

   http://gmt.soest.hawaii.edu/gmt/doc/html/surface.html

it appears to be based on more recent work of Smith and Wessel:

   Smith, W. H. F, and P. Wessel, 1990, Gridding with continuous
   curvature splines in tension, Geophysics, 55, 293-305.

So, I would say that the algorithms are not the same.

You could write some simple tests to see if you get the same
results.

Fred Clare

>
> Kind Regards,
>
> Sanjoy Som
> UW grad student
>
>
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Received on Tue Aug 22 2006 - 01:07:06 MDT