Source code for itmlogic.scatter_attenuation.ahd

import numpy as np

def ahd(td):
    """
    Returns the function F0(D) (Eqn 6.9 of "The ITS Irregular Terrain Model, version 1.2.2:
    The Algorithm") used in the computation of tropospheric scatter attenuation,
    with the input D in meters.

    Parameters
    ----------
    td : float
        Distance in meters.

    Returns
    -------
    ahd1 : float
        The returned value for function F0(D) (Eqn 6.9 of "The ITS Irregular Terrain Model,
        version 1.2.2: The Algorithm").

    """
    a = [133.4, 104.6, 71.8]
    b = [0.332e-3, 0.212e-3, 0.157e-3]
    c = [-4.343, -1.086, 2.171]

    if td <= 10e3:
        i = 0

    elif td <= 70e3:
        i = 1

    else:
        i = 2

    ahd1 = a[i] + b[i] * td + c[i] * np.log(td)

    return ahd1