Plotting Radar Data
Here is a former class project, which is now given here
as an example of plotting raster graphics.
Reflectivity values in polar coordinates is given in
KIWA.vol140.dat.gz,
and is described in format.text.
(Provided by Chris Calvert).
Your browser may automatically "gunzip" anyfile.dat.gz into anyfile.dat, and
allow you to save as anyfile.dat. It used to be that
"shift and click" allowed one to download and save as anyfile.dat.gz,
but that doesn't seem to be working for us anymore. If you save as KIWA.vol140.dat,
that is fine, you can skip the manual gunzip command provided below. If you are
curious about the decompression command gunzip, and the compression command
gzip, then you may want to visit the gzip home page.
But the basic usefullness is rather simple to understand.
gzip reversibly compresses
files to be smaller, and adds the .gz extension. For common text files, the compression
can sometimes be to about 20% of the original size. For files of numbers stored in
binary format, without reptition or patterns in the numbers,
the compression may not be much at all. For a long text file with repeating lines
of a single character, the reduction in file size is very substantial.
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A "canned" software package produced this plot .
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Here is my rendition made with
render.c,
used as so:
gunzip KIWA.vol140.dat.gz
cc -o render render.c -lm
render K*.dat
convert radar.ppm radar.png
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Radar data plotted with render.c.
The colors were extracted from the color
scheme on the right, which comes from
this NOAA site.
The color scale is slightly different from that plotted
by the "canned" software package.
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