The usefulness of radar plotting, as at present practised, may be considerably enhanced by the application of a doppler radar technique which gives instantaneous measurement of relative velocity components and quickens the whole plotting process. The range and bearing of the target are given by an ordinary radar PPI, from which the rate of change of bearing may also be determined. The doppler radar gives an immediate measurement of the radial component of relative velocity and the derivative of radial velocity: from these data the course and speed of the target may readily be determined, using an automatic computer if so desired. Possible errors in deducing the true aspect and speed are discussed and the mode of operation, and principal design parameters of suitable doppler radar are given.i. INTRODUCTION. Although the number of collisions at sea between vessels equipped with radar continues to be a matter of grave concern, there has been little real progress in recent years in the development of anti-collision techniques. Whilst it is certainly true that so-called 'radar assisted collisions' are due to misapplication of the information supplied by radar, rather than to any shortcoming in the actual radar performance, there is frequent lament that information concerning the aspect of a target is seldom readily apparent, and many mariners would place greater confidence in their radar sets if aspect information were always immediately available as part of the normal performance.Captain F. J. Wylie (this Journal, 10, ^6) has postulated three factors for the reduction of collision risk in clear weather:
The basic principles of the detection and location of objects by radar are now widely known, and the performance requirements of a marine radar equipment have already been covered by the British Ministry of Transport specification. This paper describes and analyses operational experience gained in fitting and in operating a number of equipments manufactured to this specification.
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