Any comment on arctic navigation must be broadly based since the ability to conduct voyages in ice-infested waters is influenced by many factors. The traditional technique of exploiting open channels in the ice is now no longer adequate and there is an increasing need for vessels to force ice in order to reach places and to carry out activities well inside the boundaries of the permanent ice cover during parts of the year when the sea ice is at its maximum extent.

Any device having a property which varies as a result of its being rotated in space can, in principle, be used as the primary sensor of an inertial navigation system. A wide range of devices and properties has received attention with this aim in view. The spinning-wheel gyroscope has, to date, proved the most fruitful but a number of ‘exotic’ types of gyro show promise. The discovery that the atomic nucleus can, under certain conditions, behave like a spinning mass gave birth to ideas of a nuclear gyro of some sort. The further discovery that some nuclei possess magnetic properties opened the way to nuclear magnetic resonance and offered a method of communicating with the minute spinning masses.

In recent years much time and energy has been spent investigating marine traffic flows and casualties in major seaways and rivers around the world. This paper presents data relating to marine traffic from the Humber light-vessel to the Hull Roads (Fig. 3), an intermediate seaway serving a number of small to medium sized ports.

Due to the very low power-to-weight ratio found in large deadweight ships, their high inertial values and the very long reaction time to manoeuvring commands, difficulties often arise in achieving entry to the berthing area at an exactly pre-determined speed over the ground.

This paper describes a dynamically programmed optical aid to help the navigator achieve exactly the prescribed speed over the ground as he decelerates along his traverse or intended track when approaching his terminal or swinging area. The authors are consultants to AGA Navigation Aids Ltd who have developed this device.

Over the last decade or more, some very significant changes have occurred in the general requirements relating to the handling and manoeuvring of certain classes of modern vessel in the approach to their terminal berth – whether jetty, single-buoy mooring or even when coming to anchor. The economy of size in the bulk trades has probably had the most profound effect. This often reduces the power/weight ratio of the vessel itself to a very low order. In turn this has led to radical adjustments in techniques of ship handling in the final approach phases, due to the long response time between command instructions and reactions to these by the vessel itself. When considering the inertia of a vessel of 220000 tons deadweight or more – where the feasible deceleration or rate of change of speed is also of a low order – we can see the difficulties met with when endeavouring to enter the berthing area at an exactly required pre-determined speed over the ground (as opposed to speed through the water) often as low as one tenth of a knot or less.

This paper is an abridgement of the paper presented at an Ordinary meeting of the Institute held in London on 20 February 1980 with Captain G. Dudley in the Chair. Captain T. C. Haile of the School of Navigation, City of London Polytechnic, illustrates some past instances when political issues have involved hydrographic surveys, before discussing the delicacy of position fixing in off-shore oilfields.

The political implications of hydrography can be traced back at least to the close of the fifteenth century, when the great discoveries of the Portuguese, promoted by Prince Henry the Navigator, and the discovery of America by Christopher Columbus brought to a head the rivalry between the two powers for the control of the Spice Islands of the east.

This paper was presented at a meeting of the Institute in London on 25 May 1980 with Captain S. S. D. Jones in the chair. Mr Page assesses the role of air navigation as one factor in coordinated flight planning, through the application of modern techniques, to secure maximum efficiency in airline operation and in the conservation of fuel.

This paper presents an airline view of developments in aircraft navigation and planning. It considers aircraft navigation in the widest sense together with the current change in emphasis in navigational requirements. Present technology can produce navigational systems of almost any desired accuracy – at a price. The cost of such systems, together with the requirements of ATC, will dictate the choice.

In this article formulas useful for the calculation of aircraft mid-air collision probabilities at intersecting air routes are developed. The aircraft overlap density, a key parameter in the calculation, is expressed as a function of the intersection angle of air routes, aircraft speeds, the nominal separation, and parameters in the position-error distribution. Two representative probability models for position errors are used to illustrate the computational procedures suggested. A method of approximation over large navigation systems is also proposed.

The calculation of aircraft mid-air collision probabilities is an important step in the design of air-route structure and is a key element in the specification of separation standards and minimum requirements of facilities reliability and accuracy. A thorough analysis of collision probabilities for long-range parallel air routes over oceanic areas was reported by P. G. Reich in three research documents and in a series of papers published in this Journal in 1966. Analysis of collision probabilities at intersecting air routes typical in off-shore and continental areas, however, has not been fully explored to date. The only direct reference available on this subject appears to be the work by Bellantoni,7 in which a collision problem was formulated in the three-dimensional space and was apt to deal with airport terminal landing or take-off situations. For circumstances where horizontal linear air routes intersect one another at preassigned positions, the analysis provided by Bellantoni needs to be simplified and refashioned for use in extensive applications.

The application of technological developments to the flight-deck for flight management, navigation and displays has been very rapid and there has been a tendency for parts of the operational system to be improved without evaluating fully their interaction on the flight deck and as between ATC and the aircraft. The Civil Avionics section of Operational Systems Division (FS2) at Bedford has been concerned with the development and investigation of techniques for the integration of this modern equipment into the operational environment of the flight deck of the future, with the overall aim of improving airspace utilization. This will have the potential for reducing delays and saving fuel.

Although VOR/DME has been the standard airborne navigation aid for over 15 years there are still some features of the system which are far from ideal. In particular, the bearing information from the ground station is noisy and frequently inaccurate. There are a number of sources of error, some avoidable and some not. The quality of maintenance, particularly with respect to alignment and calibration, varies greatly throughout the world – for example there have been a number of reports concerning VOR stations in the Eastern Mediterranean with up to 40° error in the transmitted bearing information.

The establishment of standards for lateral separation between adjacent jet routes depends in large part on an adequate description of aircraft path-keeping ability. While it has been accepted for many years that deviations from route centreline follow a distribution which is more peaked in the core and longer tailed than the gaussian distribution which was initially assumed, the selection of an alternative distribution is still moot. Early studies of oceanic data suggested that a double exponential distribution gave a much better description of the core data. However, this distribution still appeared to underestimate the frequency of occurrence of very large errors, so that a double-double exponential distribution was proposed and is currently used for establishment of MNPS (Minimum Navigational Performance Specification) criteria for the North Atlantic organized track system. A physical rationale for the occurrence of the double-double exponential distribution has recently been derived, with suggestions for consideration of alternative formulations.

A chart is the data base to which other navigational information is related and yet has to serve ships of widely different draughts. A possible alternative providing more draught-specific information based largely on currently available hardware, would be the creation of ‘banded contour charts’ on microfilm. Produced directly from a computer data bank by a fast flying light-spot microfilm plotter, the master charts would be single frames of 35 mm microfilm mounted in cards 183 by 83 mm. A set of micro-charts would be produced covering the same sea area and differing only in that each has a different, limited band of depth contours of critical importance to ships in a limited draught range: for example, the first going from 0 to 5 metres by 1-metre intervals, the second from 3 to 8, the third from 5 to 10 and so on. All other data, including spot depths outside the contours, would be the same on all charts in the series.

In a series of three papers Dr Lewison has described the progressive results of a line of research which may have important applications in the consideration of routing schemes. The first paper described a mathematical model which can predict the number of encounters that would occur between ships of different traffic streams in the absence of avoidance manœuvres. In the second paper the number of potential encounters was calculated from estimates of traffic flow, in a particular area of the Dover Strait, then compared with the number of actual collisions to determine the risk of a ship encounter leading to a collision. The third paper updated these results for the Dover Strait and suggested how estimates of collision risk could be made for other UK coastal areas.

It is the common practice to draw great-circle tracks on gnomonic charts, on which they appear as straight lines, to pick off the latitudes of intermediate points where the track is intersected by the charted meridians, and finally to transfer the pairs of coordinates thus measured to a Mercator chart. The purpose of this note is to present the derivation of some formulae by means of which the coordinates of points along the track may be calculated very easily.

While navigation in the Suez Canal and the Gulf of Suez has been given much study and has attracted considerable comment in recent years there has been comparatively little said about the Red Sea. In view of the very marked increase in traffic in this area and the attendant upsurge of vessels calling at Red Sea ports, particularly Jeddah, more study of the problems of navigating in this body of water would seem warranted.