The International Regulations for Preventing Collisions at Sea, 1960, became effective on 1 September 1965 and, in spite of the sound advice contained in the Annex, it already seems doubtful whether the Steering and Sailing Rules will prove efficacious in preventing collisions. It is clear that a growing body of opinion considers that changes of some sort are necessary; the April number of this Journal, for instance, contains interesting proposals by Captain J. F. Kemp.

Captain García-Frías has made the following comments on the discussion of his recent paper (this Journal, 18, 141) contributed by E. S. Calvert and S. H. Hollingdale.

Captain García-Frías observes that while Calvert and Hollingdale recognize that this paper combines his earlier suggestion for a sector rule with a set of manœuvring rules, they have failed to recognize the fundamental distinction between the structural and operational aspects of an encounter; his proposed manœuvring rules deal with the operational aspect. These rules differ from the manœuvres they have themselves proposed in that they depend only on the bearing of the target as seen on the radar at a distance of 2 miles; they derive from his sector rule and do not require a quantitative estimate of the miss distance. His rules are only the same as their manœuvres for the case of a steady bearing since their manœuvres also require the sign of the miss distance.

Many discussions have taken place regarding the feasibility of plotting when using radar in reduced visibility and it soon becomes apparent that there is confusion in what each of us considers by the term ‘plotting’.

These notes are to suggest definitions of the various stages of plotting and to consider the conditions under which each is necessary.

Radar plotting can be divided into three stages:

(a) Record plotting

(b) Deductive plotting

(c) Forecast plotting.

In Captain Wylie's note on ‘Radar as an anti-collision aid: the ultimate essentials in presentation’, masterly definition by an acknowledged expert aptly crowns the discussion which follows Commandant Oudet's paper on ‘Collisions and the Courts’ in the same issue of the Journal. It is interesting and gratifying to find in that discussion a suggestion by E. S. Calvert on manœuvres in close-quarter situations which recalls a similar proposal made by the French Institute at our first joint meeting held in London in 1957. It is that the manœuvre should be a turn of 2x° to starboard if a threat, an echo for example, is perceived x° forward of the port beam. This suggestion passed almost unnoticed at the time although it is mathematically sound if one assumes that the speed of the two vessels is the same.

In many practical situations in the field of navigation, it has been noticed that the probability distribution of measured errors has a shape which has considerable departures from that of the normal distribution. These departures are particularly noticeable in the ‘tails’ of the distribution of practical cases, which are often higher than those of the corresponding normal distributions (see, for example, ‘Is the gaussian distribution normal’, W/Cdr. E. W. Anderson. This Journal, 18, 65).

This investigation of methods used in Astronomical Navigation has been carried out by means of questionnaires completed by senior students at a few of our Navigation Schools. The data has been classified into fairly broad categories since some of it has been rather difficult to assess, due to incomplete information on such details as trading areas, which watch was being kept, and the actual time spent at sea during the year.

The discovery of the Vinland Map and the recent publication of its description* has been attended with considerable publicity on both sides of the Atlantic, in publications ranging from learned journals to glossies. Briefly, the map, provisionally dated about 1450, was discovered by an antiquarian bookseller of New Haven, Connecticut, in circumstances which so far have precluded a proper examination of its history. It has, as a recent reviewer put it, ‘no ancestors, no close relations and no descendants’. Its importance to the student of the history of navigation and discovery, however, is that (assuming it is authentic) it is by far the earliest surviving example of a map portraying any part of the Americas, and it ostensibly provides the first evidence for an early school of Norse cartography, for Vinland can clearly be identified with that part of the American continent settled by the Norsemen in the latter part of the tenth century.