Four steps to Longitude! If we chose, we might interpret the phrase by a sequence of four names: Ptolemy, Charles II, Tobias Mayer and Nevil Maskelyne—the last in 1763. But in fact the steps represent the four marine timepieces made by John Harrison—familiarly known as H1, H2, H3 and H4 of which the last proved its efficacy in 1762. The longitude was found, and by a ‘machine’, just two centuries ago. Now the bi-centenary is being celebrated by a very elegant and informative exhibition at the National Maritime Museum, Greenwich. No navigator should miss it. Even if he thinks scorn of ‘ancient history’ he owes the inventor of the first English chronometer a tribute of respect.

Training courses on marine radar simulators are held in this country at the Navigation Schools and Colleges in London, South Shields, Hull, Glasgow, Liverpool and Cardiff, with Southampton starting at some future date. The entry for each five-day course is limited to six members and places on the courses are at present generally restricted to serving masters and chief officers. The purpose of these courses is to give seagoing masters and senior officers realistic practice in manœuvring their vessels by radar in conditions of bad visibility without any of the risk involved in an actual encounter between vessels at sea, as well as risk-free opportunity to try out and test the different methods of radar presentation and plotting.

As sea traffic grows, so too does the problem of the acoustic pollution of fishing grounds. This paper describes the measurement and analysis of ship-produced underwater sounds and their effect on the behaviour of certain fishes. It would seem that their influence on marine organisms is a growing problem and should not be ignored by navigators, for the sounds produced by large or high-speed vessels, or even fishing boats, can frighten fish shoals or cause them to change their migration routes.

After a series of tests to measure and analyse the underwater sound, the output of submerged loud-speakers, either at sea or in an aquarium, was adjusted to ensure that the sound intensity near the fish was at the required level and the fish behaviour was carefully observed. For these experiments a hydrophone was connected to a pre-amplifier. A signal amplified by the pre-amplifier is attenuated before being sent to the main amplifier, the sound level being read directly on an indicator using the sound analysing character ‘C’. A tape recorder registers the sound signal in a flat response from 20 to 50 Hz to within 3 dB. A tracing recorder was also sometimes used and the two methods gave almost the same results.

This paper, which was presented at an Ordinary Meeting of the Institute in London on 21 November 1979, with S. Ratcliffe in the Chair, traces the evolution of airborne doppler navigation systems over the past two decades and discusses the treatment of errors introduced when flying over water. Both authors are with Decca Radar Ltd.

The object of this paper is to describe briefly the major developments which have taken place in doppler navigation systems during the past 15 years or so, to indicate the current state of the art and to examine in some detail the behaviour of doppler systems when flying over water. The year 1960 is taken as a starting point since by that time commercial doppler systems were established. A typical general purpose system of that generation (Fig. 1) consisted of the following units:

1. An antenna, probably mechanically stabilized.

2. A transmitter/receiver using either pulse or FMCW modulation.

3. A tracking system.

4. An analog computer.

5. A display of ground-speed and drift-angle.

6. A display of present position.

In a recent paper on shipborne radar the authors tried to analyze the mental approach of a master or pilot to the problem of handling his ship in a confined space when berthing in fog. The sense of loss that is caused by the absence of direct vision was referred to and various means by which confidence and control might be restored in these circumstances were considered. In that paper only the inadequacies of present-day shipborne radar in meeting these requirements were discussed. The approach to the problem can, however, be broadened to include the whole question of port operation in fog, and the present paper attempts to describe the general requirements and to consider in particular the role of shore-based radar and the manner in which the information obtained from radar or other aids should be presented to the master.

There are occasions when, because of the density of shipping and/or lack of sea room, ships navigating by radar in thick weather cannot avoid passing within a distance of two miles, the least distance usually considered desirable. In such a situation a simple plan of procedure and of avoiding action, if possible to devise, should greatly reduce strain on the navigator and so increase the safety of navigation generally. Also, if such a plan came to be generally followed, safety would be further enhanced, because each navigator would know what the others were likely to do.

Recently I was asked to assist the engineers in my company (a Canadian electronics firm) devise a method for using radiation from the Sun to check the alignment of heavy ground radar sets to within very fine tolerances. The degree of accuracy would have to be better than five minutes of arc in azimuth for search antennas, and three minutes of arc in elevation angle for height finding antennas. Solar radiation in the microwave region of the radio frequency spectrum would be used as a reference. The antenna reflector would be rotated in azimuth and elevation until maximum solar radiation was reflected into the waveguide horn and thence to the radar receiver. The moment peak detector current was obtained, the antenna would be locked in position and the exact G.M.T. noted. Normal astro-navigation calculation methods and tables would then be used to calculate the Sun's true azimuth and elevation angle, which would be compared with that measured by the antenna to determine its accuracy.

Since none of the engineers had previous navigation experience, they had run into difficulties when they tried to devise a method for calculating the Sun's position to within the requisite accuracy limits.

The first difficulty was the fact that most antenna calibrations would be performed by field technicians having no knowledge of astro-navigation tables and calculation methods. They would be at extremely remote radar stations across Canada and thus would not have an opportunity to ask questions if our instructions proved ambiguous.

When geophysical measurements are made from the air, it is important to know the position of the aircraft. The position at any time is usually known from a combination of position-fixing and dead-reckoning systems. In-flight optimization of this combination is a well-studied subject. When post-flight track plotting is required for geophysical survey, use can be made of both the initial and terminal position fixes to correct the dead-reckoning track and hence improve on the in-flight version. This technique is applied to compute the track of aircraft conducting ice thickness measurements in the Antarctic, and the effect of certain errors is evaluated. The algebraic results are equally applicable in parts of the world where better navigational aids are available. A relation is derived between the track plotting errors and die errors in the geophysical measurement such that the precision of one is not degraded by errors in the other.

Although the economic theory of congestion as applied to road traffic has been known since at least the time of Pigou its application to marine problems has been much slower. It is the purpose of this paper to remedy this somewhat by interpreting the theory in a marine context and to suggest some of the practical implications of taking proper account of congestion effects.

The Collision Regulations are due for revision by Imco in 1972 and already governments and other agencies are formulating proposals for consideration by its Maritime Safety Committee. The Institute's working party on the subject, which was formed initially to try to lessen the area of disagreement between people who had put forward positive proposals over the last few years, has now formed a cohesive view and formulated a set of recommendations. These are given in the interim report which follows. In the normal course of events things would have been allowed to run their course and the final report published only after further meetings of the working party which has still to reach firm conclusions on a number of points (for example on the precise form of the manœuvring diagram referred to at the end of Section 2 and in proposition (14), and on the whole question of lights). However, time is short and it seems probable that if the views of the working party are to have any effect on the deliberations of Imco, they must be made known straight away. The report (of which M. W. Richey is the author), therefore, which embodies the whole area of agreement between the members of the working party, is published here in interim form.

Dr. Calvert has expressed some unease from his own point of view about propositions (1) to (19) and it is hoped in the final report to publish an appendix by him suggesting a totally new approach to the whole problem of collision avoidance by manœuvre. It is hoped also to publish an appendix by Admiral García Frías describing the system he proposes. Both these contributions are perhaps likely to be of long-term rather than immediate significance.

The British Nautical Almanac was first published by Nevil Maskelyne, the Astronomer Royal, in 1766 for the year 1767 and the chief table in it was of lunar distances, which were tabulated at intervals of three hours to the nearest second of arc. On the bicentenary of its publication the theory and practice of lunar distance observation and reduction were reviewed in this Journal.

Captain Wylie's extensive and detailed criticisms of the Sailing and Steering Rules in the new Collision Regulations (Journal, 26, 365) were published in the January number of Navigation, the journal of the French Institute of Navigation, with an editorial note by Professor Hugon. The note and Captain Wyile's reply are given below.

In the bicentenary year of the birth of Matthew Flinders at Donington, near Boston in Lincolnshire, it is my privilege to present to Members of three notable British societies some details of the life and work of this great hydrographer.

His surveying and charting impact was made entirely in Australian waters and he is probably better remembered in that country today than he is in his homeland. It is my hope that my discourse, added to the many activities that have been arranged in Britain this year, will do something to rectify this situation. My talk will attempt to tell the brief story of Flinders' 40 years of life and work, beset in his later years by many misfortunes. I will also examine in some detail how Flinders conducted his surveys by taking a few isolated examples, and finally briefly review the results of his labours.

The views expressed in this paper are personal to the author, and not intended to represent official policy of the UK Hydrographic Office.

With the ever increasing use of electronic charts in the small craft sector, this paper is designed to give some background to developments at the United Kingdom Hydrographic Office. Included is a short review of the state of the market, with the author's view of possible future progression. The various formats of data are discussed, with a summary of the legislative background within the commercial market. This discussion is relevant, as it will ultimately shape the future market for small craft users

The Federal Aviation Administration (FAA) is developing the Local Area Augmentation System (LAAS) as a public use local area differential GPS system. The LAAS is required to support all categories of precision approach navigation. The purpose of this paper is to summarize the FAA's LAAS technical activities and programme plans. First, the complementary roles of the Wide Area Augmentation System (WAAS) and LAAS are summarized. Then technical activities are discussed, including requirements, system architecture, and flight tests. The paper concludes with a summary of the FAA's plans for LAAS, including the planned schedule of major programme activities.

The earliest record of a requirement for ships to carry lights that the author has been able to find is in the Rhodian Laws. These appear to date from about the 3rd or 2nd century B.C., and were certainly incorporated into Roman Law by A.D. 161, although Ashburner suggests that the earliest known copy dates from Byzantine times, A.D. 600–800. The Laws contain a section intended to prevent collisions between vessels under way and vessels at anchor or stopped.