Ground constants

In telecommunication, ground constants are the electrical parameters of earth, such as conductivity[?], permittivity, and magnetic permeability.

Note 1: The values of these parameters vary with the local chemical composition and density of the earth.

Note 2: For a propagating electromagnetic wave, such as a surface wave propagating along the surface of the Earth, these parameters vary with frequency and direction.

Source: from Federal Standard 1037C and from MIL-STD-188