c	file BOX.FOR
c	prog to determine the locations of the end points for the box
c	required by IONMOD_DUD & IONMOD_IRI
c
c	written by leo mcnamara 14-jul-87
c-----	last modified 16-jul-87
c
c	LINK with SPOINTS 
c
c	start point is SS% from the "TX", away from the "RX"
c	end point is EE% from the "RX", downrange
c
	ss = 10./100.
	ee = 40./100.
c
10	continue
	write(6,600)
600	format(//'   Enter coords of TX and RX for ',
     a   'circuit.....4f5.0')
	read(5,500) txlat,txlon,rxlat,rxlon
500	format(4f5.0)
	if(txlat+tlxon+rxlat+rxlon.eq.0.0) stop ' all done'
c
	flat = txlat
	flon = txlon
	glat = rxlat
	glon = rxlon
c
c	find bearing and range of circuit
	call distbear (flat,flon,glat,glon,range,bear)
	type*,' Range & bearing ',range,bear
c
c	coords of point before the TX
	bearr = bear + 180.
	if(bearr.gt.360.) bearr = bearr - 360.
	call latlon (flat,flon,ss*range,bearr,flat1,flon1)
	call distbear(flat,flon,flat1,flon1,r,b)
	type*,' TX end ',r,b
c
c	coords of point downrange from RX
	call latlon (flat,flon,(1.+ee)*range,bear,flat2,flon2)
	call distbear (glat,glon,flat2,flon2,r,b)
	type*,' Rx end ',r,b
c
	call distbear (flat1,flon1,flat2,flon2,range,bearr)
	type*,' END to END ',range,bearr
c
	write(6,602) flat1,flon1,flat2,flon2
602	format(///5x,'END COORDS  ',4f8.2///)
	go to 10
	end