Position determination at sea using low-frequency radio waves--The effect of a nearby mountain

Measurements of direction-finding (DF) error in position determination based on low-frequency (LF) radio waves were made at sea employing the Decca navigation system. The measured DF error is found to be large when a mountain is nearby. Assuming the mountain to be a hemisphere with complex dielectric constant, we evaluate DF error using electrostatic theory. Analytical predictions of the expected position error caused by the mountain's presence are qualitatively in fairly good agreement with measured values. In connection with this, fluctuations of the electric field intensities are also described.