Re: Regridding based on other arrays

[Steve Hankin <hankin@xxxxxxxxxxxxx>]

Hi Richard,

This is a very good question. You can obtain one possible solution using the
XY gridding functions, such as SCAT2GRIDGAUSS_XY. However, these functions use
brute force statistical techniques that do not incorporate information which
is implicit in the topology (rectilinear XY array) of the input data.

To meet your specifications what is needed is a new External Function
    XYAXREPLACE(V, Xcoords, Ycoords, Xax, Yax)
(named by analogy to the ZAXREPLACE function.)  The variable V (which may be
4d) on input is defined on the curvilinear coordinates defined in
Xcoords,Ycoords. The function result inherit its X and Y axes from arguments 4
and 5 respectively -- and uses an interpolation algorithm (rather than
statistics) to compute a result.

If you'd care to write such an EF (or has someone else already done so?),  I'm
sure there would be a number of grateful users!

    - steve

P.S. The inverse functionality of regridding the input variable V from its
rectilinear defining grid to new curvilinear coordinates can be achieved with
the function
    SAMPLEXY(DAT_TO_SAMPLE,XPTS,YPTS)

================

Richard Dixon wrote:

> Hello again Ferret-Users
>
> Probably another query where the answer is extrememly simple and staring
> me in the face. I have some satellite data which comprises three 640x480
> arrays:  datavalue, longitude, latitude. Currently I'm just displaying the
> data by shadind datavalue and overplotting longitude and latitude.
>
> Is there any straightforward way of regridding the data into a new array
> such that the x and y co-ordinates are longitude and latitude (like the
> usual NCEP re-analysis data, for example).
>
> Once again thanks for all your help
> Richard (still a Ferret amateur!)

--
Steve Hankin
NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115-0070
ph. (206) 526-6080 -- FAX (206) 526-6744