Ground conductivity

In the International System of Units (SI) it is measured in millisiemens per meter (mS/m).

Low frequency (30–300 kHz) and medium frequency (300–3000 kHz) radio transmissions are particularly reliant on good ground conductivity as their primary propagation is by surface wave.

[1] It also affects the real world radiation pattern of high frequency (3-30 MHz) antennas, as the so-called "takeoff angle" is not an inherent property of the antenna but a result of a ground reflection.

[2] For this reason ITU publishes an extensive world atlas of ground conductivities.

[3] Ground conductivity is sometimes used in determining the efficiency of a septic tank, using electromagnetic induction, so that contaminants do not reach the surface or nearby water supplies.