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elevation_ambiguity.pro
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elevation_ambiguity.pro
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pro elevation_ambiguity
; 2 pi ambiguity plot
bmsep = 3.24
maxbeam = 24
offset = maxbeam/2. - 0.5
C = 2.997e8
phi = -offset*bmsep + findgen(maxbeam)*bmsep
y0 = 40.
yN = 150.
dy = 5.
ny = fix((yN-y0)/dy)+1
set_plot, 'PS'
device, file='2pi.ps', /color
loadct, 1, /silent
!x.margin=[6,9]
a=findgen(17)*!pi/8.
usersym, cos(a), sin(a), /fill
sz = .5
for m=0,ny-1 do begin
; special case of Y offset only
yoff = y0 + m*dy
ioff = [0., -yoff, 0] ; offset
sep = abs(ioff[1])
nfreq = 11
tfreq = 8000. + findgen(nfreq)*1000 ; 8-18 MHz
for k=0,nfreq-1 do begin
freq = tfreq[k]
theta0 = acos((sep - C/(freq*1000.))/(cos(phi*!dtor)*sep))
if k eq 0 then begin
plot, phi, theta0/!dtor, /nodata, $
xtit='Beam Direction !7u!3!L0!N (degrees)', $
ytit='Elevation Angle !7h!3 (degrees)', $
tit='Maximum Elevation Angle for 2!7p!3 Ambiguity', $
yrange=[0,90], /ystyle
xyouts, 0,20, strtrim(fix(yoff),2)+' m', align=.5
endif
oplot, phi, theta0/!dtor
oplot, phi, theta0/!dtor, color=k*20, psym=8, symsize=sz
xyouts, !x.crange[1], theta0[maxbeam-1]/!dtor, $
' '+string(format='(f4.1)', freq/1000.)+ ' MHz'
endfor
endfor
device, /close
end