Readers of Captain Cotter's paper under this title in the April 1976 issue of the Journal may be interested in some evidence that Dutch seamen in the seventeenth century were aware of this phenomenon of ship magnetism.

Abraham de Graaf in De seven Boecken van de Groote Zeevaert, published at Amsterdam in 1658, warns ships' officers taking bearings with the compass-that metal objects in their clothing can seriously deflect the compass, and mentions iron buttons and buckles. This was an important contemporary work on navigation and de Graaf was an examiner of officers of the Dutch East Indies Company from 1679 to 1714.

The release of GNSS raw data on Android smartphones provides the potential for high-precision smartphone positioning using multi-constellation and multi-frequency signals. However, severe multipath and low observation quality in kinematic environments make double-differenced uncombined ambiguities difficult to resolve reliably. To address this, the paper proposes an improved wide-lane (WL) integer ambiguity resolution (IAR) method that combines integer rounding and the Least-Square AMBiguity Decorrelation Adjustment (LAMBDA) methods. The proposed method achieved fix rates of 57% to 70% in challenging environments, with an average improvement of 7 · 7% in horizontal positioning accuracy compared to the float solution. The traditional partial integer rounding method only improved accuracy by 1 · 1%.

Some lessons and observations experienced during a series of radar simulator courses in the period of one year are listed below:

1. The practice of plotting is generally favoured by the students and they learn quickly how to determine which targets are of concern and should be plotted and which targets may be rejected. It has to be pointed out fairly often that recordings should be taken down in an orderly manner and that—besides the time, bearing and range of a target—the heading and speed (or log reading) of the observing vessel should be written down with each set of observations.

The Executive Secretary has referred to me two notes on this subject, one by M. S. Dixon and the other by Bruno Ortlepp. Although submitted independently, and at different times, they clearly relate not only to the. same technique, but also to the same set of observations.

Now much has been recently written on the determination of time, and thus of longitude, from observations of the Moon's altitude (for example, in this Journal, reference can be made to the notes by Francis Chichester, 19, 106, 1966; D. H. Sadler, 19, 107, 1966; J. J. Evans, 19, 392, 1966; and to the comments in the article by H.M. Nautical Almanac Office in 19, 133 and 1 $2, 1966) and it should be unnecessary toNrestate either the principle or the practical disadvantages of this method.

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 recent years the Regulations for Preventing Collisions at Sea have been the subject of considerable interest to mathematicians. It has been demonstrated that the Rules as they stand are not entirely satisfactory, and this confirms a certain uneasiness which most navigators have in this respect. One of the imperfections in the Rules is that they are not universal: they do not apply in fog, when vessels are not in sight of one another, they do not apply to certain classes of vessel, they are affected by limitations of weather and sea-room, and so on. It does not seem unreasonable that a set of Rules could be devised, based on the mathematical work lately carried out, which would be more rational than the present Rules.

The present work explores the link between navigational processes and the experience of place by considering the case of Evenki reindeer herders and hunters. Our analysis shows how the idiosyncratic wayfinding methods of the Evenki result in a unique experience of place – a case that elucidates the important question of the impact of navigational processes on environmental experience, and that advances the debate between mental map theory and practical mastery theory in anthropology. We defend that their wayfinding methods – involving a particular gait, path networks, and vast hydrological and toponymical knowledge – allow the Evenki to navigate without a need for integrating egocentric and allocentric frames of reference. As a result, the Evenki experience themselves as free individuals moving through an environment that is alive and rife with possibility. This analysis reveals the ways in which wayfinding processes relying predominantly on route knowledge – as opposed to survey knowledge – affect environmental experience. Alternative methods of wayfinding can be seen as a form of resistance to the uniformisation of landscapes, and as a way of embracing the heterogeneity of space.

Autonomous vehicles rely on a combination of sensors for safe navigation around the world. For precise localisation, high-definition (HD) maps are used. These maps are a representation of the world containing information about objects on the road infrastructure. Currently, there are tens of HD map makers, however, no rigorous description of the requirements for the accuracy of HD maps has been published yet. This study fills the gap and offers a mathematical description of the minimum required accuracy for HD maps. In the first part, we identify factors that influence the quality of a map. Based on that, we proceed to present our solution for determining the minimum required accuracy for HD maps, both for static and dynamic models, and present a new formula for the minimum necessary accuracy for HD maps.

The whole question of Polynesian navigation is highly controversial. Dr. David Lewis's paper ‘Ara Moana: Stars of the Sea Road’, in the July issue of this journal, prompts me relate the story of Kau Moala in somewhat greater detail and to assess his achievements and motives, largely from his own account of his voyages.

Kau Moala was a Tongan Chief renowned for his epic feat of navigation which probably took place in the years just before 1800. The details come to us from a young English castaway named William Mariner, who spent several years in Tonga and knew Kau Moala personally. When Mariner got back to England his experiences were compiled by J. Martin and published by John Murray, London, in 1817. The work is generally known as ‘Mariner's Tonga’, the full title being An Account of the Natives of the Tonga Islands. The story of Kau Moala's famous Odyssey is given on pages 307–322 of volume I of the second edition, published in 1818. Mariner gives the Chief's name as Cow Mooaly.

The story starts with Kau Moala going from Tonga to Fiji to engage in some warlike adventures to enhance his prestige, as many another Tongan Chief had done before, and as several did later. After two years of fun and mischief he decided to return home, and set out in his large double canoe.

The idea of an ‘Altitude-Azimuth’ almanac is not new though most effort (see this Journal, Vol. 1, 185, 1948; Vol. 2, 285, 1949) has been concerned with the Sun and planets rather than the stars. For the stars the simple problem is that observations are recorded in mean time (say G.M.T.) whereas the positions of the stars depend on sidereal time (L.H.A. Aries) given by: L.H.A. Aries = G.H.A. Aries + west longitude. A full account of star tables (and diagrams) using a mean-time argument (and thus avoiding using the Almanac to give G.H.A. Aries) is given in ‘The Genesis of the E. A.N.T.s’ (this Journal, Vol. 6, 333, 1953).

This Anderson Memorial Lecture was given to the Boscombe Down branch of the Institute on 19 February 2004. In the lecture Pinky Grocott, a distinguished navigator and past President of the Institute, recounts the history of the formation of Ferry Command set up to ensure the safe and efficient delivery of aircraft from North America to the UK during World War II. He then provides personal insights into his role as a young first-tour RAF navigator employed in the Command and describes the contemporary navigation practice.

The weather is rarely out of the news. Weather can be hazardous at times almost anywhere on Earth, and the media are always keen to report dramatic events. On the global scene, weather, climate and the environment are issues of great international public concern at present because of the likely implications of increases of greenhouse gases in the atmosphere. The contributions of the meteorologist to the understanding of this global problem are increasingly recognized, as is the progress which has been made in the accuracy of day-to-day forecasts. This paper provides a brief résumé of our present ability to model and forecast the behaviour of the global atmosphere and the ocean surface, and also demonstrates how these models are applied to the practical problems of operational ship-routeing by the UK Meteorological Office. It is worth remembering that it was the very high incidence of losses at sea in the 1850s which brought about the establishment of the UK's first meteorological service.

In this paper, presented by the International Air Navigators Council, and written by its Executive Vice Chairman, the navigation of the S.S.T. is considered from the practising navigator's point of view. Extrapolating from present procedures the conclusion is drawn that navigation system verification should continue to be the responsibility of flight-deck management, that self-contained D.R. systems should be monitored by an externally referenced aid, that raw navigational data should continue to be available to the flight crew and finally that simplicity and reliability in navigation systems should be preferred to finite accuracy.

Consideration of an environment in which operational data and experience are limited to the military is a difficult assignment at the best of times. In order to discuss, with some degree of intelligence, the long-range navigation system considered desirable in the supersonic environment, we have relied mainly on the process of extrapolation using existing data and operational ‘know how’ to formulate practical guidelines.