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Re: non-ortogonal grid

Hi All,
Just a bit more between Mario and I about his data, which we thought
we'd pass on to finish this thread.  It turned out that Mario had named
a variable T, which caused most of his trouble, but there was some
useful discussion of curviilnear grids as well.

If the lon, lat temp are just one-dimensional lists of points, then the 3-argument
shade command can't use the curvilinear grid to plot the data. I'll show more
about this at the end of this message. To look at your data in Ferret try
these commands.

   yes? USE test2.cdf
   yes? show data
   yes? show grid lon

What axis is the data on?  If it's on the X axis, look
at some of the data,

    yes? list/i=1:10 temp, lon, lat

Is your variable named T?  If so, that could be
causing confusion as Ferret expects T to represent
the time coordinate of a variable.  You could either
change the name of the variable when the data is
corrected, or with ncdump and ncgen.  Or, if you
really want to use T, then it can be referenced by
putting it in single quotes:

 yes? list/i=1:10 'T', lon, lat

Ferret expects curvilinear data to be on a 2 dimensional grid,
I x J, where at each i,j point you have the latitude
and longitude
point corresponding to the curvilinear grid,
and the value of the
data field. Here is some output from a Ferret session.
The variables
GEOLON, GEOLAT, and ZVAR.  These are all on a 180x173 point
with axes XAX (i=1 to 180) and YAX (j = 1 to 173)

   yes? use lonlat.nc

   yes? show data
        currently SET data sets:
       1> ./lonlat.nc  (default)
    name     title                     I      J      K      L
    GEOLON   geographic longitude     1:180  1:173  ...    ...
    GEOLAT   geographic latitude      1:180  1:173  ...    ...
    ZVAR     variable on the grid     1:180  1:173  ...    ...

   yes? show grid geolon
       GRID GMZ1
    name       axis              # pts   start                end
    XAX       X                  180 r   1                    180
    YAX       Y                  173 r   1                    173
    normal    Z
    normal    T

     ! Visualize the lon,lat curvilinear grid
   yes? set view upper
   yes? plot/vs/sym=dot/j=140:173 geolon, geolat

     ! Shade plot of a variable on the grid
   yes? set view lower
   yes? shade/j=140:173 ztp, geolon, geolat


Mario Germano wrote:
Hi everybody,

I am experiencing difficulties in inserting grid points in a cdf file (using
FORTRAN) because these points have all different lon-lat coordinates: they
are not uniformly distributed on an orthogonal grid, but rather on a rotated
Ideally I'd like to be able to insert points one by one using a syntax like:
   insert_point(lon,lat,wind_speed, temperature,...)
I ignore if such a thing is possible.
Thanks in advance for answering my question.



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