A Brief introduction on the purpose of the paper constitutes Part 1.

Part 2 of the paper traces' the historical development of navigational radar in the United Kingdom from the beginning of the late war to the present day. The use that was made of the very early radars is mentioned and the improvement brought about by the introduction of the PPI and centimetre radar is described. An account is given of how radar assisted the Normandy landings, of the techniques employed and the lessons that were learned. It is shown how a change to shorter wavelengths improved the performance, and how this made possible a large experiment in the Scheldt Estuary designed to help convoys to reach Antwerp in fog; the navigational difficulties of this experiment are described and it is shown how an elaborate drill had to be prepared for navigating these difficult channels to allow the troubles to be overcome. The thought that was devoted to the navigational needs of the Merchant Service in peacetime is dealt with, together with the elaborate trials that were carried out in the Thames Estuary to check the plans for peacetime development. It is shown how the new equipments which were developed brought about a large improvement in performance and ease of operation. In particular, the use of new displays allowing the PPI to be superimposed on the chart is dealt with and the simplification of navigation and pilotage which this allowed; the success with which ships were navigated and piloted on radar information alone is also dealt with. Some notes are included on the work of the two first International Meetings on Radio Aids to Marine Navigation. A short account is given of some experiences with radar in Norwegian Fjords.

Part 3 describes the present position where commercial navigational radars are in production and fitted to a number of British and foreign vessels. This part compares the performance of some British and United States equipments and also compares the requirements of the British and United States Government performance specifications.

Part 4 reviews some of the problems outstanding today and makes some suggestions on possible future developments. In particular, suggestions are offered on improved PPI'S, on new systems of chart comparison, on an alternative form of display for ship-handling and, looking rather further ahead, on a new form of close range and pilotage radar.