Abstract :
The paper starts with a recapitulation in simple terms of the principal processes used in rho-theta systems, namely azimuth transmission, distance measurement and direction finding. An outline is then given of the TACAN system, illustrating the application of the processes in an established system of particular present interest. Further illustrations are taken from V.O.R. technique with particular reference to an experimental system known as V.O.R.A.C. the main purpose of which was to investigate the possibilities of improving the accuracy of the V.O.R. system while maintaining compatibility with the system in current use. Finally it is suggested that the most general form of a rho-theta system would be one giving the distance and bearing indication both in the air and on the ground, and the paper ends with speculations on the application of secondary radar technique to such a purpose.
