When harbour surveillance radars were first fitted in the United Kingdom in 1948 it became apparent that under conditions of high traffic density difficulty might arise in identifying the ship being assisted into harbour with a particular echo on the radar screen. The group at the Admiralty Signal and Radar Establishment (A.S.R.E.) working on navigational aids for the Ministry of Transport were set the task of examining the problem and suggesting a solution, and this paper will describe the results of this work.

It was with some surprise that I read Commander Sharpey-Schafer's ‘Some Notes on Astronomical Observations at Sea’ (this Journal, Vol. VI, p. 362), especially his conclusions regarding the fixing accuracy obtainable with marine sextant observations. I can makeno claim to be an experienced navigator myself, but, as a member of the staff of H.M. Nautical Almanac Office, I was privileged, in 1949, to spend three months as an observer on board H.M.S. Dalrymple, a newly-commissioned surveying ship, under the command of Captain (now Vice-Admiral Sir) A. Day.

Vice-Admiral Sir Archibald Day, the Hydrographer of the Navy, who was chairman at the Institute discussion on 15 May 1953, has received the following comments from Rear-Admiral Robert W. Knox, Assistant Director of the U.S. Coast and Geodetic Survey.

To quote the Collision Regulations—‘Risk of collision can, when circumstances permit, be ascertained by carefully watching the compass bearing of an approaching vessel.’ Most seamen are so familiar with this injunction and with the practice it describes that any particular significance in the wording probably escapes them. It is, however, important in considering the operational use of radar to note that the compass bearing and no other kind is specified and to appreciate that this is so because the relative bearing will only give quite comparable assurance when own ship maintains a perfectly steady course during the approach.

In the July number of the Journal (Vol. VI, p. 313) Captain F. J. Wylie suggested that members and other readers of the Journal should contribute their suggestions as to rules of conduct to be observed by ships using radar in fog. It is possible to print only a selection of the comment received, but all the contributions sent in have been made available to the Technical Committee.