The sight-run-sight case involves a series of two or more sights in which each sight is ‘run on’ to the time of the last sight. There are several known techniques to account for the run, which is for convenience assumed to be at a constant course. It is argued that only the GHA-Dec updating technique (GD-UT) will give a correct position solution, whereas the pre-electronic Intercept Method (IM)-based technique and its modern least-squares variant (LSQ) and the Altitude updating technique (A-UT), are proxy techniques that may yield significant deviations in position solution. GD-UT can be used in combination with a double-sight solution method for two sights and with LSQ for two or more sights. IM, LSQ and a geometric or algebraic double sight solution method applied to simultaneous double sights give identical results but the simultaneous sights case is generally an abstraction and strictly not applicable on a moving vessel.

This study aims to examine the predictors of professional commitment of the Chinese new generation, divided into post-80s and post-90s cohorts. A questionnaire survey was employed to collect data from Chinese seafaring officers of these cohorts. The results through hierarchical regression analysis present the two cohorts as having both similar and different predictors. The main difference is that company management and policies positively drive the post-80s cohort to work at sea but not the post-90s. The main similarity is that the work itself is the most important predictor for both cohorts. This study contributes to helping maritime companies to estimate the possibility of Chinese new generation officers quitting sea jobs and can be of value to both managers and authorities as they seek to comprehend the generational dynamic features to better cope with the problem of shortage of younger qualified officers.

The objective of this work was to assess whether the implementation of a bridge resource management (BRM) unit into the simulator-based nautical training of the German Navy is effective in improving non-technical skills and navigation performance. To this end, questionnaire data, observations of behaviour and performance outcomes were compared between a control group and an experimental group. Data of 24 bridge teams (126 sailors) were used for the analyses. Ten teams received BRM training and 14 teams served as the control group with unchanged simulator training. Reactions to simulator training were positive in both groups but more favourable in the control group. In the BRM group, significantly more positive attitudes towards open communication and coordination, more frequent sharing of information and fewer collisions were found than in the control group. Effect sizes were rather small. This may be due to the limited scale of the BRM unit, which consisted of only one instruction-training-feedback cycle. The extension of BRM-related feedback to all simulator runs of the nautical training can be expected to produce larger effects on attitudes, behaviour and performance.

To achieve more accurate navigation performance in the landing process, a multi-resolution visual positioning technique is proposed for landing assistance of an Unmanned Aerial System (UAS). This technique uses a captured image of an artificial landmark (e.g. barcode) to provide relative positioning information in the X, Y and Z axes, and yaw, roll and pitch orientations. A multi-resolution coding algorithm is designed to ensure the UAS will not lose the detection of the landing target due to limited visual angles or camera resolution. Simulation and real world experiments prove the performance of the proposed technique in positioning accuracy, detection accuracy, and navigation effect. Two types of UAS are used to verify the generalisation of the proposed technique. Comparison experiments to state-of-the-art techniques are also included with the results analysis.

This paper and the following five papers were presented at the NAV91 Conference on Satellite Navigation held at Church House, London, 6–8 November 1991. Copies of the conference proceedings are available from the Director, price £85 (non-members) and £65 (members).

In the last two years, the idea of a civil geostationary overlay (augmentation) to GPS and GLONASS has moved from the discussion/concept stage to something approaching reality. Many details of implementation have been or are in the process of being determined. Major developments that have taken place in this period of time include: (i) INMARSAT'S adoption of a four ocean region satellite deployment (three had been employed previously), now including one region (AOR-West) that covers the conterminous United States, (ii) Inclusion in the specifications, and contracting for, navigation repeater payloads in the four INMARSAT-3 spacecraft, now under construction, (iii) Major improvements in the Test Bed, bringing the test signals closer in function and structure to those to be provided through the INMARSAT-3 navigation payloads. (iv) Plans in the US and Europe to employ the Test Bed, or a facsimile thereof, for field trials of the GPS/GLONASS integrity channel (GIC) concept, (v) Endorsement of the ‘Wideband GIC’ concept (transmission at GPS L, frequency of a spread spectrum signal) by many members of the aviation community, (vi) Introduction and study of the possibility that the Gic might be able to carry some form of differential corrections in addition to the basic integrity and constellation augmentation functions. In other words, whereas two years ago we were still considering the possibility of a civil element of global satellite radionavigation, this year we are deeply in the process of putting the necessary elements into place.

The fisherman's task in navigating his craft are threefold:

(i) to guide his craft safely and by the most direct route between his terminal ports and the fishing grounds;

(ii) to shoot, tow and haul his fishing gear in such a manner as to prevent it being damaged or becoming fast to any obstruction on the seabed;

(iii) to search for aggregations of commercial fish species and by lures, snares and the use of towed nets to capture viable quantities of the fish located.

The navigation to and from the fishing ground poses the same problems as for other marine craft, but once on the grounds, using towed or encircling nets, the position of the nets, not only horizontally but also in the vertical plane, are as much his concern as is the position of the parent vessel. Most fishing grounds are situated where there are irregularities in the seabed topography or where oceanographical factors provide a rich feeding area for a range of fish species. Alternatively many fish species carry out an annual migratory journey to their spawning areas or towards more favourable environmental conditions, their shoaling behaviour at this time making them particularly susceptible to mass capture.

When considering the navigational performance of doppler systems it is not sufficient to examine only the inherent capability of the radar system, since the overall navigational accuracy achieved is a product of the complete ensemble—the doppler, the aircraft, its pilot, the heading reference, instrument transmission linkages, and so on.

Recently, integration of different radionavigation systems has become very popular, since it improves system integrity, availability, accuracy and reliability. This paper discusses a new, flexible and cost-effective approach to system integration, centred on a single-chip application specific processor (ASP). An overview of this integrated system is presented and the application of the ASP for the implementation of a six-channel GPS, OMEGA, Loran-C and MLS receiver is given. The ASP is currently being implemented on a 180000 transistor 1·6μ, m CMOS Sea of Gates chip, and is expected to run at 100 MHz clock speed.

The continuous data (groundspeed and drift angle) given to high accuracy by airborne doppler equipments, could be adapted for handling by automatic computers which, accepting certain other inputs, can be designed to extract a great variety of information. This paper attempts to outline the contribution that such computers could make to long-range civil air navigation.

Most navigators will, at some time or another, have noticed the effect of changes in humidity on the dimensions of paper maps or charts pinned up for display purposes. A display chart, or any other large sheet of paper, neatly pinned to a notice board in a warm dry room will tend to sag in an untidy manner if the atmosphere is allowed to become damp. Similarly a chart pinned up in a moist atmosphere is liable to contract and tear away from its anchoring pins if the weather becomes warm and dry. In the same way, the size of a paper chart in use in the air will vary appreciably with changes in atmospheric conditions; and it follows that if the size changes, so does the true scale. Such changes in the scale are of little consequence so long as dividers are used for measuring distances, since it can be assumed that the distance graduations on the chart all expand and contract in proportion to the change in size of the sheet as a whole. But if a graduated rule or straight-edge is used (and this is practicable only in the case of maps or charts based on some projection giving near-constancy of scale) then, quite apart from the scale errors of the projection, changes in the size of the chart will give rise to errors.

This paper is concerned with the preliminary localisation, orbit determination and model-based path forecasting of space debris based on a robust procedure. In this work, an in-orbit observer utilises only relative bearing observations iteratively. To this end, the problem is first formulated in order to calculate the distance vector between the space debris and any orbiting observer. Afterwards, the obtained position vector is corrected through an Extended Kalman Filter (EKF) for shrinking the sensor and process errors and increasing robustness of the computations in the presence of uncertainties. After preliminary positioning, the related classical orbital elements are acquired via the predicted position and velocity vectors using a hybrid technique. Extensive simulations demonstrate the efficacy and robustness of the aforementioned method, and in particular it is verified that the proposed scheme is capable of producing a suitable solution for preliminary localisation and orbit determination of space debris based on the presented space-based observation, which is practical in phasing and chasing manoeuvres of any grabber space robot.

John Hamilton Moore (1738–1807), a well-known teacher of navigation, was born in Edinburgh, educated in Ireland, and subsequently joined the Royal Navy at Plymouth. In about 1770 Moore established a Nautical Academy in Brentford, Middlesex, and in 1772 he published his popular epitome of navigation under the title The New Practical Navigator and Daily Assistant. Later he established himself at 127, Minories, near Tower Hill, where he not only taught navigation to ‘Gentlemen designed for, or belonging to the sea‘ but carried on the business, aided by his sons and son-in-law Robert Blachford, of chart-seller and purveyor of nautical instruments. In the preface to the twelfth (1796) edition of his Practical Navigator, Moore presumed that he had been enabled to have made gradual but progressive improvements in navigation as his ‘knowledge became extended through investigation’ and as his ‘judgement matured by experience’. In this edition of his work Moore styled himself as ‘Teacher of Navigation, Hydrographer and Chart-seller to His Royal Highness the Duke of Clarence’. There can be no doubt that Moore's Practical Navigator was favourably received; and, indeed, a twentieth edition was brought out by Joseph F. Dessiou (1790–1842), a master in the Royal Navy who, on retiring from sea-service, was employed in the Admiralty Hydrographic Office where he specialized in the study of tides. Dessiou's twentieth edition of Moore appeared in 1828, some 21 years after the death of its original author.

In urban areas, the Global Navigation Satellite System (GNSS) can lead to position errors of tens of meters due to signal obstruction and severe multipath effects. In cases of 3D-positioning, the vertical coordinate is estimated less accurately than are the horizontal coordinates. Multisensor systems can enhance navigation performance in terms of accuracy, availability, continuity and integrity. However, the addition of multiple sensors increases the system cost, and thereby the applicability to low-cost applications is limited. By using the concept of receiver clock modelling (RCM), the position estimation can be made more robust; the use of high-sensitivity (HS) GNSS receivers can improve the system availability and continuity. This paper investigates the integration of a low-cost HS GNSS receiver with an external clock in urban conditions; subsequently, the gain in the navigation performance is evaluated. GNSS kinematic data is recorded in an urban environment with multiple geodetic-grade and HS receivers. The external clock stability information is incorporated through the process noise matrix in a Kalman filter when estimating the position, velocity and time states. Results shows that the improvement in the precision of the height component and vertical velocity with both receivers is about 70% with RCM compared with the estimates obtained without applying RCM. Pertaining accuracy, the improvement in height with RCM is found to be about 70% and 50% with geodetic and HS receivers, respectively. In terms of availability, the HS receiver delivers an 100% output compared with a geodetic receiver, which provides an output 99⋅4% of the total experiment duration.

Reliable anti-collision control algorithms conforming with the rules regulating traffic at sea, the International Regulations for Preventing Collisions at Sea (COLREG), are essential for the deployment of autonomous vessels in waters shared with other ships. The development of such methods is an active field of research. However, little attention has been given to how these rules are interpreted by experienced mariners, and how such information can be parametrised for use in automatic control systems and autonomous ships. This paper presents a method for exploiting historical automatic identification system (AIS) data to characterise parameters indicating the prevalent practices at sea in encounters with high collision risk. The method has been tested on data gathered in areas off the Norwegian coast over several years. Statistics on relevant parameters from the resulting dataset and the relation between them is presented. The results indicate that the strongest influence on vessel behaviour is the type of situation, and the amount of land and grounding hazards in the vessel's proximity.

At the present time with the increase of air traffic across the Atlantic (and still more so in the future when jet aircraft will be numerous) it becomes very necessary to know what is the safe separation between aircraft, and whether some form of controlled paths may not economically be imposed between America and Europe.

In the course of a summary of established views about the still unknown origins of portolan charts (this Journal, 36, 124, 1983) the hypothesis was advanced that they originated as a result of the maritime interests of Frederick II of Hohenstaufen. It should perhaps be made clear straight away that this is no mere attempt by a German author to further German pretensions in this matter. In fact, of course, Frederick II (1194–1250) was the last emperor of the Holy Roman Empire and, according to the excellent biography by Kantorowicz, felt himself more and more the spokesman for cosmopolitan thought as his years advanced. He spent his youth in Sicily and was known as ‘The Sicilian’, and learned to speak German only during the third decade of his life during his first visit to Germany; by then he was fluent in half a dozen other languages. Sicily of course, where he spent most of his life, meant not simply the island but the kingdom of the two Sicilies which, since the Norse conquests, comprised extensive parts of southern Italy and notably Apulia, where Frederick had his court at Foggia. His dominions bordered papal territory, which accounts for the hostility to him of several popes.

The idea of portraying the accuracy of a navigational system by means of contours is very old and was first introduced to readers of this Journal by Jessell and Trow. Later writers, Sameshima, Namikawa and Hasegawa, have published accuracy contours for Loran chains. This note is a further contribution in this direction and its aim is to investigate what sort of accuracy can be achieved by marrying a position line from one chain with a position line from another.

N. Sameshima has studied the accuracy contours arising from a hyperbolic system where position lines are obtained from two pairs of stations, each pair having one station, the master station, in common. Y. Namikawa and K. Hasegawa, in a later article, constructed accuracy contours for a number of Loran chains, mainly in the Pacific, but also in the Atlantic areas. This article discusses the more difficult case where fixes are obtained through using pairs with no common station, and indicates what improvement may be expected through introducing a fourth station in a number of selected instances.

There is rich material for studying navigation technique in the fifteenth and early sixteenth centuries in the volume A Marinharia dos Descobrimentos by the late Fontoura da Costa, which deals in great detail with the evidence for early sailing methods; the facsimile reprints of rare documents bearing on early Portuguese navigation lately published by Joaquim Bensaude for the Portuguese Government also contain much information on this period. The object of this article is two-fold: to establish that in an Addendum to one of these documents, the Reportorio dos Tempos of Valentim Fernandez (1st edition 1518), we have extracts from an archaic type of navigating manual; and hence to argue that, judging from his own words, Columbus (whose skill in navigation is a matter of controversy) had studied rules and instructions for navigation just such as the Addendum contains, but that owing to his lack of elementary mathematical training he had only imperfectly understood them.

Rule 25 of the Collision Regulations lays down that, when it is safe and practicable, ships in narrow channels shall keep to the starboard side. The idea behind routing is to extend this type of organization to areas where, because of the concentration of traffic, the problem begins to resemble that of narrow channels. In the open sea a busy route presents no great problem. But where shipping lanes converge the collision problem often becomes serious. This is to a large extent a modern problem which has arisen not only with the increase in maritime traffic, but also with the ability of ships to navigate where they will. Further, the average speed of ships, in all conditions, has greatly increased.