The Terrain Profile

The terrain profile can be obtained using the NASA srtm V 4 data. This a set of terrain maps between the 60 degree parallels. There are two versions on a 100m square or 30m square on most of the land mass.

Plotting the height of each square between the Tx and the Rx we obtain a height profile for the terrain.

Where

Roughness = average terrain height.

h = array of heights along the terrain profile.

n = number heights in the profile.

We now calculate the ground impedance (zgnd).

Using:

Frequency = The frequency used for the link.

Surface Type

Polarisation = Vertical or Horizontal. Both ends must be the same.

Ground Dielectric

Ground Conductivity

Climate

The Method qlrps.

        Complex qlrps(Double fmhz, Double zsys, Double en0, Polarization ipol, Double eps, Double sgm)
        {
            const Double gma = 157e-9;
            _wn = fmhz * 0.02096436058;
            _ens = en0;
            if (zsys != 0) _ens = _ens * Math.Exp(-zsys / 9460.0);
            _gme = gma * (1 - (0.04665 * Math.Exp(_ens * 5.5772448e-3)));
            var zq = new Complex(eps, (376.62 * sgm / _wn));
            var prop_zgnd = Complex.Sqrt(zq - 1);
            if (ipol != Polarization.Horizontal) prop_zgnd = prop_zgnd / zq;
            _zgnd = prop_zgnd;
            return _zgnd;
        }     

Algorithm 1.1

k = 2 Π \ λ = f \ f0 with f0 = 47.70 MHz

λ is wavelength m and f frequency MHz

Algorithm 1.2

Ng = No * exp(zs \ z1) with z1 = 9.46 Km

No = surface resistivity reduced to sea level.

zs = general elevation over terrain profile.

Algorithm 1.3

γe = γa * (1.0 - 0.04665 * exp(Ng / N1)

N1 = 179.3 N-units,.

γa = 157 N-units/km.