Calculates the height of a radar beam as a function of elevation and range, assuming the beam is emitted at surface level.
beam_height(range, elev, k = 4/3, lat = 35, re = 6378, rp = 6357)
numeric. Slant range in m, the length of the skywave path between target and the radar antenna.
numeric. Beam elevation in degrees.
Standard refraction coefficient.
Geodetic latitude of the radar in degrees.
Earth equatorial radius in km.
Earth polar radius in km.
numeric. Beam height in m.
To account for refraction of the beam towards the earth's surface, an effective earth's radius of k * (true radius) is assumed, with k = 4/3.
The earth's radius is approximated as a point on a spheroid surface, with
re the longer equatorial radius, and
rp the shorter polar
radius. Typically uncertainties in refraction coefficient are relatively
large, making oblateness of the earth and the dependence of earth radius with
latitude only a small correction. Using default values assumes an average
earth's radius of 6371 km.
# beam height in meters at 10 km range for a 1 degree elevation beam: beam_height(10000, 1) #>  180.4081 # beam height in meters at 10 km range for a 3 and 5 degree elevation beam: beam_height(10000, c(3, 5)) #>  529.229 877.398 # define ranges from 0 to 1000000 meter (100 km), in steps of 100 m: range <- seq(0, 100000, 100) # plot the beam height of the 0.5 degree elevation beam: plot(range, beam_height(range, 0.5), ylab = "beam height [m]", xlab = "range [m]")