[ncl-talk] Regridding irregularly spaced data onto a regular grid

zilore mumba zmumba at yahoo.com
Sun Jul 27 01:11:03 MDT 2014

Thank you very much Dave. I actually saw this ncl resource but somehow I did not try it. I think it will serve my purpose. When I try the example it runs ok. Now I have to adapt it to my data and geographical area.
The thing is my mind was fixed on regridding in ncl and writing to binary and then contour in grads with which am more familiar.

On Sunday, July 27, 2014 1:24 AM, Dave Allured - NOAA Affiliate <dave.allured at noaa.gov> wrote:


Please look at the first example on the Station Data example page:

You said that you wanted to plot contours.  This simple example plots contours WITHOUT first putting data on a regular grid.  It uses a triangular mesh plotting technique.  For irregular coordinates, this technique will actually make a more accurate contour map than one made from a regular grid.

Will this example meet your needs?  My apologies if this was already discussed previously.


On Sat, Jul 26, 2014 at 4:40 PM, zilore mumba <zmumba at yahoo.com> wrote:

I have x,y,z data on an irregularly spaced geographical grid, which I want to put on a regular grid to be able to plot contours.
>My data is below (id, long., lat., rainfall).
>01  28.92  -2.47  286.5
>02  29.02  -2.68  168.8
>03  29.25  -1.67  243.4
>04  29.42  -2.07  204.9
>05  29.55  -1.58  286.9
>06  29.57  -2.48  230.
>07  29.6   -1.5   177.5
>08  29.72  -2.18  290.
>09  30.05  -1.6   206.5
>10  30.13  -1.97  178.1
>11  30.5   -2.15  156.7
>My sincere apologies because this is a question I already asked more than 6 months ago and I still have not found a solution.
>The question is: Is it possible to do what I want to do in ncl?
>1. I have tried 2dgrid.ncl which seems to but am not able to figure out how to write output to file, and the z values all seem to be above 370 (well above what I have in my file).
>2. I have try the Fortran single precision linear interpolation at Natgrid Examples and run the fortran program with ncargf77 filename I get the errors below:
>Advice will be appreciated.
>ncargf77 natgrid.f
>gfortran -fPIC -fno-second-underscore -fno-range-check -fopenmp -O natgrid.f -L/usr/local/lib -L/usr/X11R6/lib64 -lncarg -lncarg_gks -lncarg_c -lX11 -lXext -lcairo -lfontconfig -lpixman-1 -lfreetype -lexpat -lpng -lz -liconv -lXrender -lbz2
>/usr/bin/ld: cannot find -lX11
>/usr/bin/ld: cannot find -lXext
>/usr/bin/ld: cannot find -lcairo
>/usr/bin/ld: cannot find -lfontconfig
>/usr/bin/ld: cannot find -lpixman-1
>/usr/bin/ld: cannot find -lfreetype
>/usr/bin/ld: cannot find -lexpat
>/usr/bin/ld: cannot find -liconv
>/usr/bin/ld: cannot find -lXrender
>/usr/bin/ld: cannot find -lbz2
>collect2: error: ld returned 1 exit status
>Natgrid Examples
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referenced by the other modules in the documentation. Links to all
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