| ppi plot command [message #329] |
Mon, 15 June 1992 13:48 |
knight
Messages: 37
Registered: January 1992
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I want to make a ppi (plan position indicator) plot, named for the early CRT
displays that presented radar data in polar coordinates. An example is
rcs = 10.+randomu(seed,360) ; DUMMY DATA
range = [1,2] ; 2 RANGE BINS
azimuth = findgen(360) ; 1-degree AZIMUTH BINS
ppi,rcs,range,azimuth,rangebin=1,azimuthbin=1
where the ppi routine produces a polar plot with a sector at each data point
filled with a color proportional to the rcs value.
THe problem is that my first solution produces gigantic PostScript files.
The reason is that my use of polyfill makes a PostScript file filled with
vectors. The alternative of usersym uses the PostScript fill command, but
the changes in color between data points require many calls, and the unit in
usersym is a character, not the data coordinates. My third solution is
to write directly to the open PostScript file, using convert_coord to get the
proper device coordinates and then using the PostScript commands in the
idlprolog.ps. However, I need a way to get the logical unit of the open
PostSCript file, the one reported in help,/files
In summary, I have questions like:
Does anybody have an efficient ppi plotter for IDL?
Does anybody know how to get the output from help into a variable?
I'd appreciate any comments or answers. Thanks.
--
=Fred Knight (knight@ll.mit.edu) (617) 981-2027
C-483\\MIT Lincoln Laboratory\\244 Wood Street\\Lexington, MA 02173
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