This paper was first presented by the author, the National Secretary of NUMAST, at the RIN's conference on maritime Automatic Identification Systems (AIS 03) held at Church House, London, on 24/25 November 2003.

About ten years ago this author wrote the software for a suite of navigation programmes which was resident in a small hand-held computer. In the course of this work it became apparent that the standard text books of navigation were perpetuating a flawed method of calculating rhumb lines on the Earth considered as an oblate spheroid. On further investigation it became apparent that these incorrect methods were being used in programming a number of calculator/computers and satellite navigation receivers. Although the discrepancies were not large, it was disquieting to compare the results of the same rhumb line calculations from a number of such devices and find variations of some miles when the output was given, and therefore purported to be accurate, to a tenth of a mile in distance and/or a tenth of a minute of arc in position. The problem has been highlighted in the past and the references at the end of this show that a number of methods have been proposed for the amelioration of this problem. This paper summarizes formulae that the author recommends should be used for accurate solutions. Most of these may be found in standard geodetic text books, such as, but also provided are new formulae and schemes of solution which are suitable for use with computers or tables. The latter also take into account situations when a near-indeterminate solution may arise. Some examples are provided in an appendix which demonstrate the methods. The data for these problems do not refer to actual terrestrial situations but have been selected for illustrative purposes only. Practising ships' navigators will find the methods described in detail in this paper to be directly applicable to their work and also they should find ready acceptance because they are similar to current practice. In none of the references cited at the end of this paper has the practical task of calculating, using either a computer or tabular techniques, been addressed.

A number of methods have been developed to enhance the robustness of Global Positioning System (GPS) receivers when there are a limited number of visible satellites. Vector tracking is one of them. It utilizes information from all channels to aid the processing of individual channels to generate receiver positions and velocities. This paper analyzes relationships among code phase, carrier frequency, and receiver position and velocity, and presents a vector loop-tracking algorithm using an Extended Kalman filter implemented in a Matlab-based GPS software receiver. Simulated GPS signals are generated to test the proposed vector tracking method. The results show that when some of the satellites are blocked, the vector tracking loop provides better carrier frequency tracking results for the blocked signals and produces more accurate navigation solutions compared with traditional scalar tracking loops.

In this paper, the definition of seaport fairway capacity, considering port service level, is given by referring to both road and inland waterway capacity combined with the features of coastal fairways. In view of the navigation environment and ships' behaviour, the safety distance of ships entering and leaving a seaport is chosen as an overall index to evaluate the navigational safety level of a fairway. Based on the ship-following theory, an Arena-based seaport operating system simulation model is constructed to analyse the impact of safety level on seaport fairway capacity. For different navigational safety levels (i.e., minimum, general and adequate), seaport fairway capacity corresponding to different service levels and navigation durations is obtained. The results show that fairway capacity varies with safety level for a given port service level, and the lower the safety level is, the higher the fairway capacity is. Finally, a recommended navigational safety level and its associated fairway capacity are given to provide a theoretical foundation for fairway design and management.

We propose in this paper a method to enhance the performance of a coupled global positioning/inertial navigation system (GPS/INS) for land navigation applications during GPS signal loss. Our method is based on the use of an artificial neural network (ANN) to intelligently aid the GPS/INS coupled navigation system in the absence of GPS signals. The proposed enhanced GPS/INS is tested in the dynamic environment of a land vehicle navigating around a closed path on the METU campus and we provide the results. Our GPS/INS+ANN system performance is thus demonstrated with a land trial.

In a previous paper a model was outlined for an encounter between two vessels using the ‘range to domain over range rate’ (RDRR) criterion. This paper shows how the model has been developed to simulate traffic flow and collision avoidance through the main south-west bound lane of the Dover Strait traffic separation scheme. B. A. Colley and C. T. Stockel are at Plymouth Polytechnic, R. G. Curtis with the Department of Trade and Industry. The paper was presented at an ordinary meeting held in London on 16 November 1983.

This paper aims to introduce a novel approach named IMM-UKF-TFS (Interacting Multiple Model-Unscented Kalman Filter-Two Filter Smoother) to attain positional accuracy in the intelligent navigation of a manoeuvring vehicle. Here, the navigation filter is designed with an Unscented Kalman Filter (UKF), together with an Interacting Multiple Model algorithm (IMM), which estimates the state variables and handles the noise uncertainty of the manoeuvring vehicle. A model-based estimator named Two Filter Smoothing (TFS) is implemented along with the UKF-based IMM to improve positional accuracy. The performance of the proposed IMM-UKF-TFS method is verified by modelling the vehicle motion into Constant Velocity-Coordinated Turn (CV-CT), Constant Velocity – Constant Acceleration (CV-CA) and Constant Acceleration-Coordinated Turn (CA-CT) models. The simulation results proved that the proposed IMM-UKF-TFS gives better positional accuracy than the existing conventional estimators such as UKF and IMM-UKF.

The increasing volume of traffic in urban areas has resulted in steady growth of the mean driving time on fixed routes. Longer driving times lead to significantly higher transportation costs, particularly for vehicle fleets, where efficiency in the distribution of their transport tasks is important in staying competitive in the market. For bus fleets, the optimal control and command of the vehicles is, as well as the economic requirements, a basic function of their general mission. The Global Positioning System (GPS) allows reliable and accurate positioning of public transport vehicles except within the physical limitations imposed by built-up city ‘urban canyons’. With a view to the next generation of satellite positioning systems for public transport fleet management, this paper highlights the limitations imposed on current GPS systems operating in the urban canyon. The capabilities of a future positioning system operating in this type of environment are discussed. It is suggested that such a system could comprise receivers capable of integrating the Global Positioning System (GPS) and the Russian equivalent, the Global Navigation Satellite System (GLONASS), and relatively cheap dead-reckoning sensors.

We investigate a strategy to address the problem of low aircraft detection probability of space-based Automatic Dependent Surveillance-Broadcast (ADS-B). A nineteen-element hexagonal array and adaptive multi-beamforming method is proposed. This method aims to adjust the beam pattern dynamically to reduce signal collision and enlarge coverage. With the focus on the mission requirement of global aircraft detection by 2020, the appropriate gain and direction of beams are studied and designed in detail. Theoretical analysis and simulations show that this adaptive multi-beam antenna can greatly improve flight detection probability at an average reporting interval from 10 seconds to 5 seconds when compared with the traditional fixed multi-beam antenna. The results of this work show that the design of a 19-element antenna along with the adaptive multi-beamforming method can be considered as a building block of future space-based ADS-B.

The observability of error states in Inertial Navigation System/Global Positioning System (INS/GPS) integration is of great importance. Rank tests or null space tests of the observability matrix have been adopted by previous works, however, for a time-varying system with a high-dimension error state vector, it is very difficult to analyse the observability matrix by these traditional methods. In this paper, the decoupled observability analysis method is proposed for an 18-dimensional INS/GPS integration system. By reducing the dimension of coupling error states, several six-dimensional decoupled observability sub-matrices are obtained, which make the observability analyses easier. The observability results of error states are obtained by the proposed method. Covariance simulation with an Extended Kalman filter (EKF) and a flying test were performed which confirmed the theoretical results.

Demonstrations and local tests of several maritime autonomous surface ships (MASS) have recently been carried out. From a technological standpoint, MASS are becoming able to handle actual operations in certain sea areas. Since 2017, the MSC (Maritime Safety Committee) of the IMO (International Maritime Organization) has been discussing legal problems with the Regulations for Preventing Collisions at Sea (COLREGs) with regard to MASS operation. The purpose of this paper is to clarify the rules from the perspective of seafarers, who need to interpret COLREGs when dealing with MASS in ship handling situations on the sea, and also to discuss possible required amendments to COLREGs. This paper attempts to clarify the extent of current interpretations while also taking into account the answers to questionnaires received from 130 pilots, ship captains and navigation officers concerning COLREGs for MASS operation. Given the four common principles of COLREGs, it is considered whether the principles need to be changed with the introduction of MASS from the viewpoint of seafarers.

Recently, a basic pattern of coast seaway system networking has been established in China. As a result, a large number of precautionary areas will be gradually established. Because of the high frequency of ships' encounters and accidents, these precautionary areas have been a weak but important facet of ships' routeing. Navigational Traffic Conflict Technique (NTCT) was introduced to quantitatively evaluate the safety of precautionary areas. Focusing on traffic conflict, the calculation method of navigational traffic conflict points is discussed, and a comparison analysis of the two editions (2002 and 2008) of Yangtze estuary ships’ routeing is performed. Then the automatic acquisition system of navigational traffic conflict data that can be used in the quantitative analysis of the influence degree of a single traffic flow on the whole precautionary area safety is developed, and the left-turning traffic flows of Yangtze estuary ships’ routeing precautionary areas B are taken as an example. This article establishes a foundation for the precautionary area safety analysis system, and provides the decision basis for policy making in optimisation of geometric design and traffic organisation of precautionary areas.

In this study, possible ionospheric precursors of the Mw7·1 Van earthquake are investigated with temporal, spatial and spectral analyses. For this purpose, Global Navigation Satellite System (GNSS) data of 11 International GNSS Service (IGS) stations and 17 Turkish National Permanent Real-Time Kinematic (RTK) Network (TNPGN-Active) stations were utilised. In addition, Global Ionosphere Map (GIM) data produced by the Center for Orbit Determination in Europe (CODE) was used to obtain GIM-vertical Total Electron Content (vTEC) values for the epicentre. The results of the temporal and spectral analysis indicate an increase (2–8 Total Electron Content Units (TECU)) before the Van earthquake occurred on 9 October, 15–16 October and 21–23 October within 15 days, 8–9 days and 1–3 days prior to the earthquake. The Cross-Wavelet Transform (CWT) method was used to examine the presence of correlation between noticeable variations and space-weather. It is deduced from the CWT analysis that the anomalies should originate from either solar effects or the Van earthquake due to coupling between the F10·7 solar activity index and TEC variations on the anomaly days. The results demonstrate that interdisciplinary approaches and various methods including frequency domain could be used to determine the presence of an earthquake-related anomaly in the ionosphere accurately.

Demands on security, safety, and environmental protection in worldwide shipping are steadily increasing. Shipboard broadcast transponders based on the Automatic Identification System (AIS) can be easily detected close to coastal or waterway areas. Satellite-based AIS receivers detect globally but are limited in high-density traffic areas. This paper investigates the challenges and performance of AIS detection on aircraft at altitudes between 8 500 m and 10 000 m. During flight trials over sea and land, AIS signals were recorded. Post-processing of the recorded data allows the evaluation but also faces challenges due to the nature of overlapping AIS signals at the aircraft. A comparison of detected signals at the aircraft with received AIS signals on the ground is given, including the evaluation of the reception footprint of the aircraft. Finally, a concept for worldwide AIS detection via airliners is presented. The study shows the potential for global complementary surveillance coverage via airliner-based AIS detection.

Zero velocity update (ZUPT) is widely discussed for error restriction in land vehicle Inertial Navigation Systems (INSs) and wearable pedestrian INSs to overcome the problems of Global Positioning System (GPS) unavailability in urban canyons or indoor scenarios. In this paper, an online smoothing method for ZUPT-aided INSs is presented. By introducing the Rauch–Tung–Striebel (RTS) smoothing method into the ZUPT-aided INS, position errors can be effectively restrained not only at stop points but during the whole trajectory. By integrating reverse navigation with a ZUPT smoother, the method realises forward and real-time processing. Compared with existing approaches, it can improve the position accuracy in real time without any other sensors, which is well suited for applications on high-accuracy navigation in GPS-challenging environments. Accuracy test results with different Inertial Measurement Units (IMUs) show that the developed method can significantly decrease position errors from hundreds or thousands of metres to below ten metres. During the whole trajectory, the online smoothing method ensures the maximum position errors at non-stop points can reach the same level of accuracy at stop points. A delay test result proves that the delay of the reverse online smoothing method proposed in this paper is much shorter than existing online smoothing methods.

This paper proposes a simplified algorithm for reducing the computational load of the conventional underwater integrated navigation system. The system usually comprises a three-dimensional accelerometer, a three-dimensional gyroscope, a three-dimensional Doppler Velocity Log (DVL) and a data fusion algorithm, such as a Kalman Filter (KF). Since the expected variations of roll, pitch and depth are small, these quantities are assumed to be constant, and the proposed system is designed in a two-dimensional form. Due to the low speed of the vehicle, the nonlinear dynamic equation of the velocity can be simplified in a linear form. We also simplify the conventional KF in order to avoid matrix multiplications and matrix inversions. The performance of the designed system is evaluated in a sea trial by an Autonomous Underwater Vehicle (AUV). The results show that the proposed system can significantly reduce the computational load of the conventional integrated navigation system without a significant reduction in position and velocity accuracy.

Enhanced Loran (eLoran) is currently being implemented to provide back up to global navigation satellite systems (GNSS) in many critical and essential applications. In order to accomplish this, eLoran needs to provide a high level of availability throughout its desired coverage area. While the current Loran system is generally capable of accomplishing this, worldwide, there remain a number of known areas where improved coverage is desirable or necessary. One example is in the middle of the continental United States where the transmitter density is not adequate for providing the desired availability for applications such as aviation in some parts. This paper examines the use of lower power, existing assets such as differential GPS (DGPS) and Ground Wave Emergency Network (GWEN) stations to enhance coverage and fill these gaps. Two areas covered by the paper are the feasibility and performance benefits of using the antennas at these sites.

Using DGPS, GWEN or other existing low frequency (LF) broadcast towers requires the consideration of several factors. The first is the ability of the transmitting equipment to efficiently broadcast on these antennas, which are significantly shorter than those at a Loran station. Recent tests at the US Coast Guard Loran Support Unit (LSU) demonstrated the performance of a more efficient transmitter. This technology allows for the effective use of smaller antennas at lower power levels. Second is the ability to broadcast a navigation signal that is compatible with the Loran system and the potential DPGS broadcast (when using a DGPS antenna). The paper examines some possibilities for navigation signals. The goal is to develop a suitable low power signal that enhances navigation and is feasible for the transmission system.

The second part of the paper examines the benefits of using these stations. The benefits depend on the location of the stations and the ability seamlessly to integrate them within the existing Loran infrastructure. Analysis of these factors is presented and the coverage benefits are examined.

In our paper The Risk Homeostasis Theory1, it was accepted that the behaviour of people involved in the operation of cargo carrying ships is conditioned to maximize the economic benefits of the amount of risk assumed in the transport. As a follow-up to that paper, the objective of this one is to investigate the relationship between the level of compliance of the cargo carrying vessels with international standards and the degree of severity of the incidents they are involved in. For this purpose, we analyse the same sample of 2,584 cargo carrying ships involved in incidents during 2005 and 2006 used in that investigation. The variables of the Paris MoU to identify substandard ships are used again to measure the standard level of ships and the degree of seriousness of incidents is determined by the number of days ships are under repair.

We utilised precision Global Positioning System (GPS) tracking to examine the homing paths of pigeons (Columba livia) released 20 times consecutively 25 km from the loft. By the end of the training phase, birds had developed highly stereotyped yet individually distinct routes home, with detailed recapitulation evident at each stage of the journey. Following training, birds also participated in a series of releases from novel sites at perpendicular distances of up to 3 km from their established routes. Results showed that subjects were attracted back to their established routes and recapitulated them from the point of contact. Naïve conspecifics (yoked controls) released from the same off-route sites confirmed that the experienced birds' route choices were not influenced by constraints exerted by terrain features, but that increased experience with the general area conferred a homing advantage in the form of more efficient flight tracks, even from these novel sites. Patterns in the paths taken by experienced birds to rejoin their established routes are discussed with reference to navigational mechanisms employed by homing pigeons in their familiar area.

The Chairman of the Sea Safety Group has most kindly agreed to the publication of this definitive paper on the hazards to be encountered by mariners when transiting the Dover Strait. The paper brings together the deliberations of the SSG Navigation Panel and the best information available to them sent from all quarters of the sharp end of the marine industry to produce a paper which provides a centre for discussion on this difficult and controversial issue. The Sea Safety Group retains the copyright.