The objective of this paper is to illustrate a methodology for the enhancement of meteorological marine forecasts tailored to the needs of navigation. The study consists of two parts: (1) Theoretical background. Introduction to numerical models for weather forecasting used by meteorological centres. A review of the most reliable equations for prediction of intensity and direction of wind and sea state. In particular, reference is made to the tables for wind forecasting developed by R. Mayençon and A. Pezzoli and the equations for prediction of sea state obtained by K. Haselman and D. J. T. Carter in light of the JONSWAP experiment. (2) Practical application. Application of the methodology to a real-world example: a weather forecast elaborated by the Meteohydrological Laboratory at Dipartimento d'Idraulica Trasporti ed Infrastrutture Civili (DITIC) of the Polytechnic of Turin. The forecast was requested by the Consorzio Prada Challenge 2000 as a meteorological support for the training they held in the Tyrrhenian Sea for the next America's Cup series.

Over the recent decades, there have been a number of trends that have driven the desire to improve the ability to position and navigate in all environments. While GPS has been the driving factor behind most of these trends, there are limitations to GPS that have become more evident over time as the World has increasingly come to rely on location. These limitations are mostly due to the low transmission power of GPS satellites, where navigation signals broadcast from space are comparatively weak, especially by the time they have travelled to receivers on the ground. This makes the signals particularly vulnerable to fading in difficult environments such as built-up urban areas. The low signal-to-noise ratio (SNR) also means that the signals are susceptible to jamming, both hostile and accidental.

This motivates the need for non-GPS (or, more generally, non-GNSS) navigation technologies, for example, terrestrial based alternatives to GNSS such as eLoran. But, there is also significant interest in the exploitation of other non-navigation signals for positioning and navigation purposes. These so-called ‘Signals of Opportunity’ (SoOP) do not generally require any alterations to existing communications transmission infrastructure and often use alternative multi-carrier modulation techniques to those methods used by most GNSS services. The major challenge of using a SoOP for location purposes is that the transmitter network infrastructure has not generally been designed with positioning as a requirement.

An ongoing project, at the Institute of Engineering Surveying and Space Geodesy (IESSG) of the University of Nottingham, is directed towards an investigation of the potential of the Digital Audio Broadcast (DAB) signal for positioning purposes. A prototype Software Defined Radio (SDR) DAB positioning receiver has been developed and has now been tested. This paper presents a detailed review of the structure of the DAB signals and explains how these signals can be used as the basis of a positioning system. In addition the development of the prototype SDR receiver and the initial results are presented and discussed.

Real multi-Autonomous Underwater Vehicle (AUV) cooperative systems operate in complicated marine environments. The interaction between a multi-AUV cooperative system and its marine environment will affect the reliability of the system. Current is an important influencing factor of multi-AUV cooperative systems. A reliability index of multi-AUV cooperative systems known as System Reliable Probability (SRP) is proposed in this study. A method to calculate SRP is introduced, and the influence of current on SRP is discussed in detail. Current is considered an attack source, and the degree of its influence on SRP is calculated. As an example, the performance of this method is shown on two multi-AUV cooperative systems. Results show that the influence of the same current environment on different structures of the multi-AUV cooperative systems differs. This result provides a reference for the structure selection of multi-AUV systems. This study provides a practical method to estimate the reliability of multi-AUV cooperative systems.

Array antenna beam forming has high potential to improve the performance of the global navigation satellite system (GNSS) in urban areas. However, the widespread application of array antennas for GNSS multipath mitigation is restricted by many factors, such as the complexity of the system, the computation load and conflicts between required performance, cost budget and limited room for the antenna placement. The scope of this work is triplicate. (1) The pre-correlation beam forming structure is first suggested for multipath mitigation to decrease the system complexity. (2) With the pre-correlation structure, the equivalence of adaptive beam forming to quiescent beam forming is revealed. Therefore, the computational load for beam forming is greatly decreased. (3) A theoretical model is established to link the benefits of beam forming with GNSS performance improvement in terms of pseudorange quality. The model can be used by industry to balance the aforementioned restrictions. Numerical results with different array settings are given, and a 2 × 2 rectangle array with $0.4\lambda $ element spacing is suggested as a cost-effective choice in GNSS positioning applications in urban canyon areas.

The ability of animals to find their way, without the benefit of mechanical or electronic aids to navigation, has fascinated humans for centuries. Relying on innate knowledge, coupled with the extraction of navigational data from the natural features of the universe, animals continually confound humans with their skills in locomotion. The magnetic compass, sun compass, strip maps, snapshots, target maps, temperature charts and star charts are known to feature in the overall animal navigation kit. Each species selects the most appropriate ‘map/chart’ and navigation kit for its environment.

Procedures based on solutions of the direct and inverse geodetic problems are presented and their application in orthodromic and loxodromic navigation is analysed. They can be used in traditional navigation during a route planning and during sailing on the planned route in real time. The optimal division of orthodromes during planning and locally predicted short loxodromes during sailing – which allow orthodromic navigation also in manual steering – are proposed.

Although multiple global navigation satellite systems (multi-GNSS) with more visible satellites have a high success rate, they make positioning time-consuming. Partial ambiguity resolution (PAR) can improve the efficiency of multi-GNSS; however, at present PAR cannot simultaneously achieve fast and high-precision positioning with a high success rate. Therefore, PAR based on ambiguity dilution of precision- and convex-hull-based satellite selection is proposed. The experimental results of the proposed PAR, its corresponding satellite selection algorithm, the classical PAR, and the low-cutoff-elevation-angle-based multi-GNSS show that the proposed PAR outperforms the classical PAR, i.e., it achieves fast and high-precision positioning with a success rate of 100⋅0%. Furthermore, in terms of R-ratio-test-based ambiguity validation, it improves the reliability of carrier-phase-based integrity monitoring of multi-GNSS and the corresponding satellite selection algorithms. In addition, its positioning accuracy is close to that of multi-GNSS and higher than that of the classical PAR, with maximum differences of 0⋅3 and 2⋅4 cm, respectively. The proposed single (dual) frequency-based PAR improves single/dual-frequency multi-GNSS efficiency by more than 54⋅9%/80⋅4% (42⋅0%/75⋅8%) when 14⋅4 (13⋅2) out of 24⋅4 satellites are selected.

This paper discusses the main issues of today's maritime navigation and its safety and security systems. Fast development of sciences and technologies, further fast development in the shipping industry, but mainly the appearance of the new very dangerous threats at sea that appeared at the beginning of this century, deeply influence the safety and security of maritime navigation and its systems. These factors are the main reasons for writing this paper.

Since the large-scale development of offshore oil installations started in the 1970s the requirements for navigating men and machines around structures and on the sea bed have increased dramatically.

The earliest forms of navigation were by tracking with fish-finding sonar, either directly or with the aid of an acoustic transponder. The sonar would usually be fitted to a surface craft, whose position was found by using one of the commercial navigation systems such as HIFIX. The range and bearing of the object being tracked was then applied to this position. Most of this work was done by hand and the position up-date rate was of the order of minutes. The error of position was the sum of the surface system and tracking system errors and was of the order of at least 10 m.

Columbus's first voyage to America has been widely regarded as a considerable feat of navigation. Feat it certainly was, but the great advances in navigation during the fifteenth century were in fact made by the Portuguese, whose adaptation and development of Mediterranean methods to the more demanding requirements of the ocean made the European voyages of discovery possible. It was in Portugal too, probably during the years 1478–85, that Columbus acquired his knowledge of navigation. This paper, which was presented to a meeting at Brown University, USA on 26 September 1989, where the author was Gulbenkian Research Fellow at the John Carter Brown Library, examines navigational practice in the Mediterranean during the late middle ages and its subsequent development during the Great Age of Discovery.

Navigation is a human activity with the aim being to arrive at a predetermined destination. In order to find the way to the destination, the use of current input from the actual environment while travelling is needed as well as stored and organized knowledge of the local geography. Although the knowledge requirement has been studied extensively in the form of cognitive maps or other spatial representation, few studies deal with how the knowledge is used together with the input from the actual environment while navigating.

In a previous article in this Journal mention was made of an unexamined manuscript by Hariot belonging to the Petworth Collection entitled The Doctrine of Nauticall Triangles Compendious, which promised to be of interest to navigators. When Lord Leconfield, the owner of the Collection, heard of this he very kindly himself brought this manuscript to the British Museum for study there, and meanwhile Dr. Shirley of the United States, who is at work on other aspects of Hariot's life, sent over from America a transcript from a microfilm copy which was in his possession. The contents of the manuscript more than fulfilled expectation, for it appeared that the main theme was the computation of meridional parts for drawing a Mercator chart and, as Mr. Sadler, the Superintendent of H.M. Nautical Almanac Office, shows in the second part of this paper, Hariot was remarkably in advance of his time in his mathematical treatment of this problem, which continued to be a favourite one for discussion until the discovery of the calculus. As is well known, the first table of meridional parts to be published was that compiled (by simple addition of secants) by Edward Wright (1558–1615) of Caius College, Cambridge, a mathematician who had been nautical adviser to the Earl of Cumberland, and on occasion to the Lord High Admiral himself.

CAPTAIN JAMES COOK is deservedly esteemed as a great seaman, and he must be acclaimed also in the more particular role of a great navigator. For although he made no specific contribution to the art of navigation as such, he advanced it by sheer force of character. It was, indeed, a task for the mathematicians and astronomers, not for the sailors, to lay down new principles and new observations or calculations by which a ship's position could be found and her course directed when at sea. And it was for the mathematical and optical instrument-makers to design and perfect the instruments by which such observations could be made. But, in the last resort, everything depended upon the ships' captains, the masters and the pilots. They alone could decide whether some novel principle should be mastered, some new instrument actually used. ‘We have piped unto you and ye have not danced’ is a cry which echoes through the ages. For the sailor was not alone in turning a deaf ear to the advice of public men, scientists and his own professional instructors. He was hostile to change, he preferred some old rule of thumb. And this is to be expected from all such men as learn the actual practice of their trade or craft by working beside an experienced master who in turn is passing on the traditions of an earlier generation.

The principal characteristics of the GLONASS system, its current status and deployment outlook are considered. Comparison of the main characteristics of the GPS/GLONASS systems from the user's viewpoint is made. Proposals focused on the operations to be carried out to improve navigation determination accuracy for the users, provided with the combined equipment, are given. The data presented, received simultaneously on the user&s GLONASS equipment and a GP–500 GPS system, indicate that navigational determination accuracies of both systems are approximately equal. The key characteristics of 6–channel user facilities for civil aircraft and helicopters are presented. This equipment has been developed in the Institute of Space Device Engineering (ISDE) in accordance with a standard draft ARING on the combined system. The principal directions of the accuracy characteristic of the GLONASS system updating are considered. It is suggested to use the quantum–optical measurements on the Etalon satellite, launched into GLONASS satellite orbit, so that ephemeris information can be improved. The questions concerning supplying the system integrity and differential corrections information are discussed. It is proposed to combine the global system of integrity signal generation and transmission with differential corrections for regional systems. The version of the information frame developed in ISDE and intended for transmission of this information to users via geostationary satellites by means of signals similar to GPS/GLONASS, and without additional complication of user equipment, is presented here.

As Professor Taylor has described, the Hariot ms. is largely concerned with the calculation of meridional parts. These calculations are of great interest not only as regards the question of priority, but also because they are based on a method which was more than fifty years in advance of contemporary mathematical knowledge. Although the ms. is paged and cross-referenced, the calculations are incomplete and inadequately explained; arithmetical errors (remarkably few when all calculations had to be done by long multiplication!) make absolute interpretation of all figures almost impossible. Considerable detail is thus unavoidable if the essential parts of the ms. are to be put on record and explained; though the most important point must be left unexplained. There can be little doubt that Hariot's calculations are original and independent.

The high seas freedom of navigation, and the lesser rights of transit, archipelagic sea lane and innocent passage applicable in straits used for international navigation, archipelagic sea lanes and the territorial sea respectively, have been said to embrace two notions: ‘one is the right to make progress over the surface of the sea, the other is the duty to make progress only in an orderly way, as to speed, steering, lights and so on – the manner of operation of the right’.

A ship's perception of risk is an important basis for collision avoidance. To improve such perception, several risk measurement parameters on the ship domain are determined, including the approach factor, the time to domain violation (TDV) and the possible collision domain. Then, a risk hierarchy prewarning (RHP) model based on the violation detection of a ship domain is proposed, in which a two-level alarm scheme is adopted accordingly. A low-intensity alarm will be activated by reaching the minimum approach factor and the TDV threshold, and a high-intensity alarm will be activated by the factor of the possible collision domain and the TDV threshold. Subsequently, a novel guard zone in ARPA radar utilising the RHP model has been developed to establish a ship's risk perception system for officers on watch at sea. The model proposed in this paper can not only enhance the veracity of risk assessment around our own ship, but also be used as a decision support system for collision avoidance.

Aiming at improving the poor real-time performance of existing nonlinear filtering algorithms applied to spacecraft autonomous navigation based on Global Positioning System (GPS) measurements and simplifying the algorithm design of navigation algorithms, a spacecraft autonomous navigation algorithm based on polytopic linear differential inclusion is proposed in this paper. Firstly, it is demonstrated that the nonlinear estimation error system of spacecraft autonomous navigation can be modelled as a polytopic linear differential inclusion system model according to the idea of global linearization. Thus, the filtering of a nonlinear system simplified to a filtering of a polytopic linear system with coefficients. Secondly, Tensor-Product (TP) model transformation is applied to determine the polytopic linear differential inclusion system model. The model error introduced by global linearization is reduced and the compromise between computational complexity and modelling accuracy is realised. Finally, a spacecraft autonomous navigation algorithm based on polytopic linear differential inclusion is designed by combining multi-model Kalman filtering with data fusion. Compared with an Extended Kalman Filter (EKF), the proposed algorithm is simpler and easier to implement since it need not update the Jacobian matrices online. Simulation results demonstrate the same estimation accuracy of the proposed algorithm to that of EKF.

The layout of seafloor datum points is the key to constructing the seafloor geodetic datum network, and a reliable underwater positioning model is the prerequisite for achieving precise deployment of the datum points. The traditional average sound speed positioning model is generally adopted in underwater positioning due to its simple and efficient algorithm, but it is sensitive to incident angle related errors, which lead to unreliable positioning results. Based on the relationship between incident angle and sound speed, the sound speed function model considering the incident angle has been established. Results show that the accuracy of positioning is easily affected by errors related to the incident angle; the new average sound speed correction model based on the incident angle proposed in this paper is used to significantly improve the underwater positioning accuracy.