Re: newbie, netCDF/isocontour/SpreadSheet ?'s.

• To: visad-list@xxxxxxxxxxxxx
• Subject: Re: newbie, netCDF/isocontour/SpreadSheet ?'s.
• From: "From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>" <billh@xxxxxxxxxxxxx>
• Date: Thu, 10 Jun 1999 14:40:03 -0500 (CDT)

Hi Roland,
 
> I have a netCDF file
> (ftp://ftp.cdc.noaa.gov/Public/rhs/visad/ball50.nc)
> which is basically a cube (50x50x50) full of zeros except for a
> three areas in the shape of crude spheres where the values have
> been set to 15, 35 or 45 respectively.
>
> The metadata of the file has been faked up to resemble that of
> our standard netCDF files for atmospheric and oceanic climate
> data.  This file has three spatial coordinate variables and a
> time (record) dimension with three time steps.
>
> When I read the netCDF file into the SpreadSheet and the
> default mapping makes perfect sense, with longitude, latitude
> and depth mapped to x, y and z, time mapped to animation and
> the field variable mapped to iso-contour.
>
> The SpreadSheet displays a box in cell A1 and the scales on
> the box when displayed appear to make sense, but no matter
> what value I choose for the iso-contour I don't see anything
> displayed in interior of the box.
 
I finally got a chance to look at your file.  Each 3-D grid
consists of primarily missing values, with three spherical
regions of constant values (15, 35 and 45), just as you
described.  Iso-contours are drawn between adjacent grid
points with values above and below the iso-level.  However, in
your data adjacent grid points either have equal values, or
one value is missing, so no iso-contours are drawn.
 
You can view your data by deleting the mapping from 'ball' to
'IsoContour' and adding a mapping from 'ball' to 'RGB' or to
'RGBA' (using the SpreadSheet's edit mappings dialog).  If you
map to RGB, you'll need to select 'point mode' - otherwise you'll
just see a black cube.
 
Cheers,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html