摘要:

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.

DOI:10.1049/pi-b-1.1958.0033

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper indicates the progress in development and usage of long-range radio aids to navigation in the last decade, and is almost exclusively concerned with air navigation. Some indication is given of the changing operational requirements, and of the extent to which the choice of future aids is likely to be affected by them and by economic and international considerations.The main features and anticipated performance of new aids are summarized, and particular reference is made to aids which are in an advanced state of development but have not been the subject of papers presented to The Institution.The conclusions reached are that for at least 10 years considerable use will be made of self-contained aids, utilizing Doppler or inertia principles, particularly for air navigation. Ground-based systems will still need to be used to complement the self-contained aids, and for marine purposes where justified. Economic considerations, however, are likely to limit the deployment of the more expensive ground-based systems to those regions or routes where particular problems of congestion or navigation arise, and these considerations will doubtless govern the final choice of such an aid.

DOI:10.1049/pi-b-1.1958.0036

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper discusses the present use of the Decca Navigator radio position-fixing system as a marine and aircraft navigational aid. The permanent navigational service currently comprises 12 chains and some 4000 ship and aircraft installations; in addition, mobile chains are used for surveying and exploration. The absence of modulation permits close spacing of the chain frequencies. The receivers contain a reference system giving a common phase datum for all users.The system is a c.w. hyperbolic one in which, in ships, the fixing co-ordinates are normally indicated as phase-meter (Decometer) readings. Aircraft normally use an automatic plotter driven from the receiver by an impulse-motor servo system. There are several different types of airborne receiver, and for certain airborne applications a servo system imparting an inertial characteristic to the displayed data is employed. The system can be combined with a navigational aid of the Doppler type to form the Dian system, and the Dectra long-range aid, also part of Dian, has common ground and airborne equipment with the parent Decca Navigator system. A recent development includes a zone-identification facility and employs a new form of transmission that substantially increases the range at which lane identification is effective at night.

DOI:10.1049/pi-b-1.1958.0037

出版商:IEE    

年代:1958

数据来源: IET

摘要:

This paper describes a self-contained radio navigation aid for aircraft which works by virtue of the Doppler principle. Ground speed and drift angle are determined by measuring the Doppler shifts that occur when signals transmitted from a moving aircraft are reflected back from the ground along two or more beams. Ground speed with an error of less than 0.2% and drift angle with an error of less than 0.2° can be obtained with suitable equipment.Drift angle is combined with heading from the aircraft compass to give direction of travel with respect to north, and this information together with ground speed is fed to a unit which computes the aircraft's present position. In general it is found that the accuracy of the indicated position is limited by the accuracy of the aircraft compass.Descriptions are given of the various units of the system, including an aerial which simplifies the problem of obtaining adequate accuracy. The errors are analysed and experimental results are given of those that occur over sea.An account is given of the experimental equipment that was built and tested at the Royal Radar Establishment and which formed the basis of equipments now in production.

DOI:10.1049/pi-b-1.1958.0038

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper gives an account of Airborne Radio Installation 5851, the first Doppler navigation equipment to be used by the Royal Air Force.The way in which the requirements of the specification are met is described, and an account is given of the special features which have been incorporated in the design.The performance and reliability under Service conditions are discussed.

DOI:10.1049/pi-b-1.1958.0039

出版商:IEE    

年代:1958

数据来源: IET

摘要:

A low-power c.w. Doppler navigation aid is described which has been designed for use in maritime reconnaissance aircraft. Low-voltage klystrons combined with high-gain fixed aerials provide adequate system gain for operating over all surfaces except the calmest water. Display is in the form of drum counters showing distance flown along heading and distance drifted at right angles to heading, port or starboard. Accuracy of measuring these distances is within ±1% of the total distance flown.

DOI:10.1049/pi-b-1.1958.0040

出版商:IEE    

年代:1958

数据来源: IET

摘要:

By measuring forces and moments that constrain a body of known inertial characteristics to move with a vehicle it is possible to determine acceleration in a set of specified axes and hence change in velocity and position. The principles of this method of navigation, known asinertial navigation, are outlined, and it is shown that the many possibilities of a practical realization can all be expressed in terms of a single block schematic of a computer which corrects for the expected variations in the specific force of gravity as a function of position and time.The magnitude of the problem of designing suitable gyroscopes and accelerometers is discussed, and the effect is calculated of certain errors in the components. Means for combining inertial navigation with radio navigation aids are outlined, and it is shown that these give an effective memory over periods in which the radio aid may be inoperative, a heavy filtering of the radio-aid output without introducing lag and loss of information, and interpolation between outputs of a low-data-rate system. The performance requirements for gyroscopes and accelerometers to obtain this can be much less stringent than for pure inertial navigation.

DOI:10.1049/pi-b-1.1958.0041

出版商:IEE    

年代:1958

数据来源: IET

摘要:

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.

DOI:10.1049/pi-b-1.1958.0044

出版商:IEE    

年代:1958

数据来源: IET

摘要:

TACAN is the latest form of rho-theta navigation system for aircraft and embodies certain novel features.The system characteristics are briefly described and a short history of its beginning and development are given.Basic principles of operation are followed by a description of the apparatus required, and the advantages of the system for bad site operation is discussed. Additional facilities are described, such as data link and approach aid integrated with TACAN, and a summary of the system advantages is given.

DOI:10.1049/pi-b-1.1958.0045

出版商:IEE    

年代:1958

数据来源: IET

摘要:

Direction-finding practice in Britain is reviewed over the frequency band 10kc/s–400Mc/s; the survey is restricted to land-based systems. Current applications are outlined, the factors affecting accuracy are discussed with particular reference to those concerned with propagation, and equipment is described.The applications are numerous, ranging from location of thunderstorms at the lowest frequencies to widespread aeronautical uses at the highest frequencies. Over the lower parts of the frequency range the effects of the ionosphere on accuracy have to be borne in mind in many of the applications. In the v.h.f. and u.h.f. bands these limitations are absent for short-range working and the accuracy is determined largely by site and instrumental properties.The majority of direction-finders in current use have fixed aerial systems, the most common being the Adcock type. At the lower frequencies, however, loops are used, and wide-aperture systems having circular arrays of aerial elements are rinding application at the higher frequencies. Regarding the display of bearing information, although some use is still made of the aural-null method, automatic presentation of the bearing either on a meter or on a cathode-ray tube is generally employed. For aeronautical purposes in the v.h.f. and u.h.f. bands, where development has been particularly marked, remote control of the equipment and remote display of the bearings (on a number of frequencies simultaneously, if required) are of increasing importance. The paper also includes a description of automatic position-fixing systems for which these remotely operated instruments are especially adapted.

DOI:10.1049/pi-b-1.1958.0046

出版商:IEE    

年代:1958

数据来源: IET