Rho-theta system

A navigation system in which one or more signals are emitted from a facility (or colocated facilities) to produce simultaneous indication of bearing and distance. Since a bearing is a radial line of position and a distance is a circular line of position, the rho-theta system always ensures a position fix produced by the intersection of two lines of position which are at right angles to each other. This produces a minimum geometric dilution of position, a figure of merit for all radio navigation systems, and is one of the chief advantages of a rho-theta system. Another major advantage is that it is a single-site system and can thus be installed on a ship or an island. This has also made it attractive politically, enabling small countries to have their own navigation systems. See also Doppler VOR; Electronic navigation systems; VOR (VHF omnidirectional range).