When we started surveying Megalithic sites in Britain we used a cloth tape, but after some years it was realized that it was necessary to be more precise and now we use a steel tape for the important sites. Similarly with astronomy; at first we considered it sufficiently accurate to work to ¼° but now we know that it is advisable to work always to within a minute of arc. This is because we have found out that the erectors of the stones sometimes used distant foresights, either artificial or natural, and by using these they could get an accuracy of better than a minute. The method of observing was for the operator to watch the edge of the celestial body grazing a foresight or running down the edge of a hill. He moved sideways until he got exact coincidence and then marked the position. This first came to our attention when we measured up the site at Ballochroy on the west side of Kintyre.

Like so many Americans in this Bicentennial Year I find myself reflecting more and more on our heritage, the present state of affairs and our future. As Director of the Defense Mapping Agency I am especially aware that I am in a line of succession that can be traced back to Robert Erskine, the first Geographer-Surveyor to the Continental Army under command of George Washington. This has naturally impressed upon me the more than 200-year service that my organization and its predecessors have rendered to the Armed Forces of the United States, and incidentally our maritime fleet.

The north-east coast of Australia is fronted by the world's longest coral reef system, which stretches in a north/south direction between latitudes 9° and 24° South. Although its outer limit is at distances of between 20 and 120 miles from the coast the enclosed waters are relatively shallow and contain many islands, detached reefs and shoals. The shipping lane between the coast and the Great Barrier Reef is known as the Inner Route. Torres Strait, its northern entrance, although extensive is shallow throughout and encumbered by reefs and islands to such an extent that only one route through it has been lit. The alternative routes are shallow or tortuous.

For a long while now positions on the surface of the Earth have been fixed by observing the altitudes of two heavenly bodies. The equations:

include on their left-hand side two observed zenith distances and on their right-hand sides the required values of latitude and longitude. The history of celestial navigation records many different solutions to the problem, one of them being the observation of equal altitudes of the same body east and west of the meridian, usually the Sun, or of two different stars. If only the local time is required it is not even necessary to measure the exact altitude.

The NAVSTAR Global Positioning System (GPS) is a satellite-based navigation system that will provide extremely accurate three-dimensional position fixes and timing information to properly equipped users anywhere on or near the Earth. The system will be available continuously regardless of weather conditions and will find extensive utilization in improved weapons delivery accuracies, range instrumentation, &c. Furthermore it will provide an ultimate saving in the number and cost of navigation and position-fixing systems currently employed or projected. It is a Joint Service programme managed by the U.S.A.F. with deputies from the Navy, Army and Marines and the Defense Mapping Agency. The system concept evolved from U.S.A.F. and Navy studies initiated in the mid-1960s. Current programme plans call for the deployment of six satellites in 1977 to permit demonstration and evaluation tests over the continental United States. The system will then be expanded through the deployment of additional satellites into an operational 24-satellite system.

There has been, and always will be, some debate about Marconi's probable mood when in the summer of 1897 he left Italy by train for London, where his new invention was at last to find the encouragement and financial backing needed for its practical realization. His enthusiasm must have been damped by a marginal note by the Italian Minister of Posts and Telegraphs in his report on the historical experiment at Pontecchio—that young Marconi should have himself admitted into a well-known Roman clinic for mental diseases!

In the very near future there is a good chance of being able to navigate around the world using one or more of the radio navigation aids currently being implemented. Navigators the world over have long dreamt of a reliable, global, all weather navigational tool and this is now within their grasp. This paper discusses some of the administrative tasks that must be accomplished to make the navigator's dream come true. There are a multitude of radio navigational aids, so many in fact that the U.S. Government has become critical of the technical and user community for the proliferation of these systems. However for global radio navigation the field is narrowed considerably, there being only five contenders.

Practical inertial navigation is a quite recent achievement, only twenty-five years for serious research and development and only five for its commercial use. However, one might possibly say that a partial understanding of some of its principles is much more ancient. For example, in the Bible1 we read that God used a plumb-line to identify a particular location!

The increase in the number and tonnage of modern vessels, the large differences in their handling qualities, the dimensions of straits and ports, and consequently navigation difficulties encountered in poor visibility, have led the authorities involved to set up control centres responsible for the functions of traffic regulation and aids to navigation. Several systems ensuring these functions have been set up over the last few years or are currently under way. Using modern technology these systems meet a wide range of operational requirements and are characterized by extensive modularity, allowing system implementation in successive stages.

To optimize the man-machine relationship different approaches are possible, the adaptation of man to the machine or of the machine to man. The first relates to training and selection, the second is generally called ‘human engineering’, now of great interest both in the naval and merchant marine context. Changing factors like the density of traffic in harbours, the harbour environment, the speed of ships and problems of manning and automation have all contributed to that interest. A ship designer is increasingly confronted with design problems where the man/machine relationship involves the operator as a controller. The desired increase in performance is achieved only if human possibilities are put to their best use.

Marine traffic engineering is a new field of navigation study with a history ranging over some fifteen years. The first traffic survey fully deserving of the name was carried out by Yamaguchi et al in 1963 in Japan; more than 30 surveys a year are nowadays being carried out with the cooperation of the Maritime Safety Agency, the Japanese Association for Preventing Sea Casualties and the Marine Traffic Engineering Research Group. The number of papers on the subject in the Journal of the Japanese Institute of Navigation has increased correspondingly. Table I gives a breakdown of theoretical studies of marine traffic engineering. A general account of Japanese activity in these fields has been published in different papers in the Journal of Navigation, London, and emphasis in this paper is based on activities since 1970.

Between April and about September 1977 almost all the present buoys in the southern North Sea, Dover Strait and eastern part of the English Channel will be changed and a completely new system introduced in an area much used by international shipping of all types. Why has this come about and how can the new system be recognized on charts and in the water? What are the most significant changes and where will the system be applicable? The answers to these questions are given in the Hydrographic Department's new publication NP 735, IALA Maritime Buoyage System A, Edition 1, 1976, which is now available from Admiralty chart agents. It should be studied carefully by all who go to sea or are concerned with marine operations in north-west European waters.

This paper by the Principal Scientific Officer of Trinity House was presented at an Institute meeting in London on 28 April 1976 with Mrs. Mary Pera in the Chair.

Mr. Reynolds describes the use of lights to convey positional and other information by the assignment of characteristics of rhythm and colour and discusses the problems of visual discrimination, the choice of light intensities and the effect of atmospheric conditions on the ranges of lights. He also describes the new buoyage system and other moves towards international agreement. A paper on the IALA system by the Hydro-grapher of the Navy appears at p. 94.

Lighting is used in various ways in maritime applications. For operations at night in vessels, in harbours or on drilling platforms general lighting is necessary; such lights may also be of value in indicating a hazard or suggesting a route to be followed but are not expressly intended for that purpose. Fixed lights in vessels are arranged in a spatial pattern and employ colour to give indications of the presence and aspect of the vessel to other vessels. Indirect lighting is also sometimes used, as in the floodlighting of lighthouse towers to reduce bird deaths by collision.

In this paper the author sketches the historical development of radar beacons: the different types are classified in relation to code and frequency employed and the benefits and drawbacks of more recently proposed types of beacon are discussed.

The paper was presented at a Marine Electronics Symposium sponsored by the Society of Electronic and Radio Technicians at the University of Southampton in July 1976.

The military use of responder beacons before 1945 led to secondary radar systems, such as Rebecca-Eureka, Oboe, and IFF, giving facilities for target location at long range with an accuracy and identification not available from a primary radar system. The desirability of these advantages in civilian systems was recognized but the absence of military urgency and considerations of cost led to delay. Although responder beacons became an essential part of the Air Traffic Control System, extension into the marine field did not succeed until the U.K. Ministry of Transport Safety of Navigation Committee set up a Technical Committee and Working Party in 1962 to investigate the conditions governing the marine installation of responder beacons as a navigational aid. This committee recommended that responder beacons (alternatively called racons) should be set up to an agreed specification at selected sites around the UK coast, to become the first civil marine navigational racon system. The co-operation of the Admiralty Surface Weapons Establishment, Trinity House, and Kelvin Hughes made possible the installation and operation of three racons—on the Liverpool Bar LV, the Kish LV, and St. Abb's Head LH—to provide operational experience on which the committee's recommendations were based, followed by the setting up of the complete system.

Anyone concerned with navigation, be he practising navigator, design or development engineer, teacher, or amateur yachtsman, will be aware that the great majority of developments took place prior to Captain Cook's epic voyages (1768–1779) or after 1904 when the first radio time signals were transmitted. During the first period the science of astro-navigation had been developed and such aids as log, chronometer, sextant and Nautical Almanac were available. The methods developed during that period differ very little from the traditional methods which are still in use today.