Rho-theta system of air navigation

This is the classical system of navigation employed by geographical surveyors, in which distance from the poles is marked off along the parallels and direction round the poles is marked off by the meridians with the zero meridian passing through Greenwich. In the system adopted by the International Civil Aviation Organization the center of the system is the location of the aerials of the apparatus. Directional information is obtained by a special airborne receiver operated from the transmissions of the omni-directional radio range, and distance is determined by an airborne interrogator-responder operating in conjunction with a ground transponder beacon. The equipments required, their method of use and advantages of this system are considered.