For most ship navigators, this discussion is now purely academic – which does not make it less interesting.

In an earlier study, the author attempted to give some quantitative estimates of the problems that free flow might face in Europe. The study was based on a traffic sample from the Eurocontrol Route Charges Office for a busy day in 1991. More recently, they generously made available a similar sample for a day in 1997. Using this new data, the study has been extended to cover wider aspects of the free flow problem. The central problem is that of ensuring safety. This will require a mechanism to detect collision threats and safely to resolve the problems. Possible tools are ground-based surveillance and/or airborne systems. This paper will use computer modelling to predict the loads that these detection and resolution systems must face.

One of the first occasions that navigators became aware of the potential problem generated by the (then) recently-invented radar, was the so-called radar-assisted collision which occurred outside of New York between the Stockholm and the Andrea Doria in 1956. Forty-seven lives were lost in the Andrea Doria and five on the Stockholm.

Radar (Radio Detection And Range) had been invented and began its sea service during the Second World War. Its use had been, as its name implied, to give initial warning of, and the range of, another vessel on a simple Cathode Ray Tube. As the system was enhanced and the Plan Position Indicator (PPI) style of display came into prominence, complete stretches of the coastline were shown. Its usage was enhanced so that ships began to be navigated by radar. However, the navigator himself was still very much in touch with the natural elements, through the very open design of the bridge at that time.

Following the Stockholm/Andrea Doria tragedy, navigators came to terms with the fact that their PPI view of the world was a relative one rather than the actual world. Plotting the observations became the norm.

This paper was presented at the Third Electronic Chart Technology Conference, SASMEX International, Brighton, 22–23 April 1998.

Electronic Chart Systems have been used by mariners across the entire user spectrum without official standards or specifications for 10 years. In the last three years, the debate has centred on chart data and the merits of differing cartographic technologies. There is little new that can be said for or against raster or vector technologies except what actual users might say to support the requirements of their day-to-day operations. Today, we approach a new stage as ENCs start to become available but only for limited areas. This in turn means that ENCs are capable of supporting the only approved electronic chart system, ECDIS, in a limited way. There is an urgent need for alternatives to ECDIS to cover those areas where ENCs will continue to be unavailable for the foreseeable future. This paper therefore summarizes a feedback from users of RCDS and ECDIS-type systems to demonstrate the benefits which can be secured from official recognition of RCDS systems as the legal equivalent of paper chart navigation.

In anticipation of the TOTAL Solar Eclipse on 11 August 1999 (see the January/February issue of Navigation News), it seemed very appropriate to repeat this short article by one of the Institute's most respected Fellows. It was first published in Vol. VII, October 1954.

A TOTAL eclipse of the Sun provides an opportunity, rare though it may be, of obtaining an instantaneous fix from the Sun alone. Eclipses vary greatly in character, in position on the Earth, in the width of the path of totality, in the duration, and also in the direction of the path. However, the shadow of the Moon cast by the Sun is always a right circular cone which, in the case of a total eclipse, intersects the Earth's surface at some point before its vertex. Owing to the motion of the Moon in its orbit round the Earth, the shadow moves at a speed of about 2000 m.p.h. from west to east (it varies considerably according to the distance of the Moon from the Earth). The intersection of this cone with the Earth's surface is an ellipse, which moves over the surface at speeds which are very high when the cone is nearly tangential (i.e. when the Sun's altitude is low) and at speeds as low as about 1000 m.p.h., when the eclipse is central over the equator at noon and the Earth's rotation has its maximum effect. The speed of the shadow is generally low enough to give a position line of considerable accuracy from the observed time of either second or third contacts, that is the beginning or ending of the total phase. An error of 1 second corresponds, in the most favourable case, to about one-third of a mile. The position line is, of course, the portion of the elliptic shadow corresponding to the observed phase and time; these can be precomputed.

The 1998 International Conference of the Royal Institute of Navigation was held at Church House, Westminster, London on 9–11 December 1998. The full proceedings, Comprising the following papers, can be obtained from the RIN Director (£45 to Members, £65 to non-Members. Both exclusive of p & p).