interpolation techniques

Hello,

For some time now, I have successfully been using gsn_csm_contour_map to
create contour maps of my irregularly spaced ice core data from
Greenland. Now I would like to create interpolated data equivalent to
what one would get by picking points from the maps created by
gsn_csm_contour_map (effectively what I imagine gsn_csm_contour_map is
creating internally before plotting the contours). I've seen that
natgrid appears to be the recommended function for creating regular
grids from irregularly spaced data. Assuming natgrid really is the
appropriate function for this task, what I'd like to know before I
invest more time on this:
(a) If I were to contour the new output grid, would it produce a map
reasonably close to what I get now using gsn_csm_contour_map and my
original data? I'm not expecting them to be *identical* but I do want
them to pass a reasonable "those look similar" test.
(b) The natgrid output grid is rectangular so I'm anticipating the
possibility of extrapolation outside the spatial range of my input data
-- is this going to happen and is there any advice for dealing with this
situation?
(c) I'm working with lat/long in a polar region, so I'm not quite sure
how to create the output points so that they are equally spaced -- do I
need to be thinking about converting from lat/long to an equal area grid?

By the way, the link to further docs on Natgrid on the page for the
natgrid function appears to be broken, i.e., the link w/in the text "
This function is part of the Natgrid
<http://www.ncarg.ucar.edu/ngdoc/ng/ngmath/natgrid/nnhome.html>
package...". See this page:
http://www.ncl.ucar.edu/Document/Functions/Built-in/natgrid.shtml

Thanks,
Dave

-- 
517 Deike Building
Earth & Environmental Systems Institute
Penn State University
University Park, PA 16802

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Received on Fri Nov 16 2007 - 08:41:29 MST