A review of radio aids to aeronautical and marine navigation

Abstract

The paper is an introduction to the Convention on Radio Aids to Aeronautical and Marine Navigation.The parts of the radio-frequency spectrum which are in use for navigational purposes extend from about 10kc/s to 40Gc/s. The basic factors which apply to all radio-navigational technique are the wave-path, measurement of time interval, the wave propagation velocity, base-line distance and aerial aperture. For short-distance navigation the predominating source of error is usually in the measurement of time interval, but at greater distances it is due to an inexact knowledge of the wave propagation velocity.The navigational requirements of ships and aircraft are similar, but the means of meeting these requirements differ, because ship navigation involves movement in two dimensions and aircraft in three dimensions. For example, this has caused the design of shipborne and airfield radar aerials to differ appreciably. Development of radar in frequency bands above 30Gc/s is continuing in order to obtain systems with greater resolving power, but at these frequencies the high-energy absorption during heavy rain is a handicap to their use.Self-contained aids to navigation such as dead reckoning, Doppler and inertia navigation involve integration processes, the errors being dependent upon the quality of the information used and the integration time. They have a wide field of application over the undeveloped parts of the world, but in areas of high traffic density, their ability to give adequate protection against collision is obscure. In consequence, navigational techniques which define a common co-ordinate system to all users within their coverage are preferred. The V.H.F. Omnmi-Range, Tacan and Dectra systems are mentioned as examples of these techniques.A section deals with precision navigation which applies to the landing of aircraft and the berthing of ships. The suggestion is made that pilot vessels should be fitted with high-precision radar for berthing operations, and v.h.f. television links should be used to assist the pilot of the vessel being berthed.The paper concludes with a look into possible future fields of application and mentions high-stability frequency sources and artificial earth satellites as devices which may be used in the future to assist navigation.