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.

What are the major factors contributing to ship accidents, and how do these factors evolve in the long term? This study addresses these two questions by leveraging an unsupervised machine learning method named structural topic modelling to identify the causes of ship accidents. The study analysed 2,341 task errors manually collected from 441 reports issued by four government agencies covering a 45-year time span. The results show that the structure of causes of ship accidents remained essentially the same during this period. This highlights the social-material aspect of navigation technology, indicating that the use of advanced technology may not necessarily lead to safer navigation practices, and the interaction between the technology and human agency must be focused on in the bridge management context. Additionally, the computer-assisted textual data analysis highlights pilot-related factors, which might be rooted in the unsupervised and difficult-to-verify handover procedures between pilots and captains, thereby underlining the importance of appropriate piloting regulations.

Multipath propagation can cause significant impairments to the performance of Global Navigation Satellite System (GNSS) receivers and is often the dominant source of accuracy degradation for high precision GNSS applications. Commonly used time-of-arrival estimation techniques cannot provide the required estimation accuracy in severely dense multipath environments such as urban canyons. Multipath components are highly correlated and this results in a rank deficiency of the signal autocorrelation matrix. In this paper the Doppler spectrum broadening of the fast fading channel resulting from the motion of the receiver or surrounding objects is employed to decorrelate signal reflections for the purpose of high-resolution estimation of multipath delays through the subspace-based Multiple Signal Classification (MUSIC) technique. Specifically, delay-domain correlator outputs at different Doppler frequencies are combined to enhance the rank of the signal autocorrelation matrix. Simulation and results of real data collected in an urban environment (downtown Calgary) are presented to compare the performance of the proposed method with the spatial-temporal-diversity-based MUSIC technique and a widely available algorithm in commercial GNSS receivers, namely the double-delta correlator technique. The performance metrics are based upon pseudorange and positioning errors, which are derived using an accurate reference trajectory established using a high precision GNSS-INS integrated system.

Complex domestic airspace requires collision risk models and monitoring tools suitable for arbitrary aircraft trajectories. This paper presents a new mathematically based collision risk approach that extends the International Civil Aviation Organisation (ICAO) models to full aircraft encounters based on real trajectory data. A new continuous time intervention model is presented, along with a position uncertainty propagation model that better reflects aircraft behaviour and allows generalisation to all trajectories to eliminate degenerate cases. The proposed risk model is computationally efficient compared to the models it is based on and can be applied to large-scale trajectory data. The utility of the model is demonstrated through a series of case studies using real aircraft trajectories.

Signal-In-Space Error (SISE) is important for the system integrity of GNSS. Real-time monitoring SISE has been one of the effective solutions used for improving GNSS system-level integrity. As one of the typical solutions, the Galileo integrity concept uses Signal-In-Space Accuracy (SISA) and Signal-In-Space Monitoring Accuracy (SISMA) respectively to transmit the quality of SIS and the integrity alarming information to users. As an important component of the Galileo Integrity Concept, Worst User Location (WUL) is of great importance for the computation of SISA and SISMA. An improved WUL algorithm based on a geometrical model is given in this paper, which needs no iterative search and is simple when compared with the existing models. The WUL accuracy requirement is discussed based on an analysis of the magnitude of the orbit errors and SIS ranging resolution and error. The conclusion is that, considering the metre-level orbital error observed in the orbit determination process, as long as the orientation error of the WUL is less than three degrees, the projection error of SISE can be kept to centimetre levels. This will satisfy the requirements of most users. The algorithm is further optimised to omit the non-linear iterative parts based on the above assumption. The optimisation reduces computation load and enhances the real-time capability. GPS raw measurements are used to validate the correctness and reliability of the algorithms.

The problem of errors in radar plotting were considered by Capt. H. Topley (11, 167) and Capt. F. J. Wylie (12, 198), and it was shown that the error in the estimated distance of the C.P.A. depends upon mean range and range change in plotting interval. I want to introduce the term rate of error in the estimated distance of C.P.A., in the same way that Topley shows the percentage error in the estimated speed.

In December 1981 the European Environmental Bureau (EEB) published a Memorandum on Shipping and the Environment, of which the following is a condensed version. Prior to publication, the Memorandum was favourably discussed at a one-day EEB Workshop on Shipping and the Environment, held in London, on 23 October 1981, and attended by representatives of the European Commission, the Marine Environment and Maritime Safety Divisions of the International Maritime Organization and shipping interests. The EEB is an independent, international liaison body which coordinates the activities of some sixty non-governmental environmental organizations operating in all the member States of the European Economic Community (EEC).

The EEB Memorandum intends to put into perspective various recent initiatives by the European Commission aimed at curbing pollution of the sea by ships, as well as improving maritime safety. These initiatives concern the development of a Community information system for marine oil pollution prevention and abatement, together with an advisory committee; the establishment of Port State control; and the adoption of a concerted action project on shore-based maritime navigation aid systems through European Cooperation in the field of Scientific and Technical research (the so-called COST-301 project).

After examining the complementary roles of worldwide and regional arrangements for maritime safety and the prevention of vessel-source pollution, and in particular the distinct but related functions of IMO and EEC in this regard, the EEB Memorandum indicates two major aspects of ship safety and pollution control: the inspection of vessels in port, to ensure compliance with generally agreed safety standards, and offshore vessel traffic management in areas of safety and pollution hazard.

This paper discusses the drawbacks of observational methods of analysing navigational errors and shows the advantages of a synthesizing technique, whereby the effect of any change in the magnitude and distribution of a component error upon the overall resultant error can be evaluated and examined. To this end a computer program has been developed which is capable of accepting both analytical and numerical statistical distributions, representing errors in the components, and combining them to yield the overall effective error. A new error distribution better representative of many navigational error distributions is introduced. The work described is applicable to the investigation of any error which depends upon the interaction of many component errors and is not restricted to the navigation field. An extension of the method to mixed samples is indicated.

The paper describes the final step in the development of a universal computer program aimed at synthesizing navigational errors in order that they can be used in evaluating their effect on any proposed A.T.C. system. The investigation was commenced at the College of Aeronautics in 1963 and has been the subject of several published papers during the interim period.

This paper describes a low-cost, in-vehicle route planning and driver information system being developed for use within the DRIVE PLEIADES (London–Paris corridor) project. The system integrates vehicle position information from a GPS receiver, traffic condition messages broadcast from both RDS-TMC and radio paging, and road network information from a route planning system. Instructions describing the route to be followed are presented to the driver on a dashboard-mounted LCD and in spoken form. The system tracks the calculated optimum route and gives instructions for the next section of the route to be covered. The optimum route is continuously recalculated, reacting to TMC messages and the vehicle's location.

A well-known navigational method is to determine position through observation of the highest altitude of the Sun at noon. This procedure is based tacitly on the assumption that the observed altitude is a symmetrical function of time about the highest point which appears thus in the meridian. In order to examine the accuracy of this approximation for a fast moving ship, let us consider the situation in more detail. The equations will be formulated using the standard functions in a modern pocket calculator and its application modules.

Knowledge of the statistics of aircraft vertical speeds is important both for the construction of realistic traffic simulators and for the development of trajectory prediction tools for use in future air traffic control (ATC) systems. This paper reports on the analysis of radar data recordings for nearly 10000 civil flights on airways. Results are presented for the means and spreads of vertical speeds as functions of altitude. Evidence is presented that roughly half of the observed spreads arise from fluctuations within each aircraft's trajectory, as opposed to variation from one aircraft to another. A simple procedure is proposed for simulating vertical speed data which has statistics similar to those obtained from the radar recordings. Some consequences of the results for the development of trajectory prediction tools for use in future ATC systems are discussed. The results suggest that the provision of accurate trajectory prediction tools is not as straightforward as it might at first appear to be.

It is clearly not possible, in the space of one paper, even to touch on all aspects of interplanetary navigation, and some whole fields must be ruled out from the start. This paper will not be concerned with any discussion of the space-flight as such; there is no point in considering navigational problems at all unless one can assume (at least for the sake of argument) that there is to be some practicable way of lifting a ship out of the Earth's gravitational field, and then of accelerating it out of the Earth's orbit; but even granting this major premise a considerable amount of selection is still essential.

Some apology, or at least an adequate excuse, is needed for resurrecting a theoretical treatment of the effect of coriolis acceleration on observations of altitude made with a bubble sextant. Such an excuse is provided by the recent publication by Dr. J. J. Green of an article suggesting that the correction table (Z-correction) given in both the British and American Air Almanacs (and in many other Air Almanacs) is incomplete. In a reasoned letter to the Editor of Navigation, Dr. G. M. Clemence, Director of the American Nautical Almanac Office, has given a simple and straightforward explanation of the two separate and distinct causes for the deviation of the zenith as indicated by the bubble of a bubble sextant; and he has further justified the present practice adopted in the almanacs. Considerable interest has, however, been aroused and it seems opportune to give a previously unpublished general derivation of the theoretical correction, together with a brief discussion of the difficulties of practical application.

The situation today can be described as very frustrating for a variety of reasons. Air traffic flow-management (ATFM) has dominated the scene for many years since its conception in 1980. At that time, the principles of ATFM were directed at ensuring that temporary or isolated sector overloads could be handled by ATC and only when broad, prolonged overloads were expected was ATFM activated. Today, we have the reverse situation, where ATFM is active throughout 16 h or more during each day. The system as such was never intended or planned to cope with such a burden and the results are seen in a variety of forms, including departure delays as shown in Fig. 1.

A research and development programme performed in Sweden over a period of 9 years has created a substantial know-how on the design of satellite navigation user systems. Thus, a basic user system, called the GP & c Total System has been developed and tested over 3 years. This system can serve as a basis for the tailoring of an almost endless number of applications. The system is currently using data from the GPS satellites, but can also be operated with combined GPS/GLONASS receivers. The Swedish GP & c System is an example of how the communication, navigation and surveillance (CNS) concept and the various elements (ADS, ATM, etc.) for a new global Air Navigation System published by the ICAO FANS Committee can be implemented and integrated into a user-friendly operational system. The ICAO 10th Air Navigation Conference (5–20 September 1991) endorsed the FANS concept in which the main elements are based on the implementation of satellite navigation technology.

This paper examines the evolution of the arctic submarine and the ever-increasing scientific and commercial potential which have accompanied this evolution over the past 340 years. It is a sporadic history of arctic submarine ideas, concepts and actual experiences with vessels at sea. It happens to be a history that is largely American, with important additions as a result of the experiences of the Germans, Soviets and the British, particularly during World War II. Finally, it is a history in which five early visionaries in particular stand out: Bishop John Wilkins of England; Jules Verne of France; Professor Anschutz-Kampfe of Germany; the submarine designer Simon Lake, of the United States — whose influence extended over four decades until well into the twentieth century; and Sir Hubert Wilkins of Australia.

The standard formulae, assuming a spherical Earth, for converting distance on a rhumb-line track into differences of latitude and longitude are:

where C is the course and α is known as the middle latitude. It is approximately the mean latitude when both points are on the same side of the equator; tables of the correction to be applied to the mean latitude to give the middle latitude are given in most collections of nautical tables.

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.

This paper starts with a brief overview of cross-rate interference (CRI) and methods developed in the past for estimating the CRI between two Group Repetition Intervals (GRIS). It presents an algorithm for fast calculation of the loss of pulses due to blanking in dual-rate stations. These stations broadcast on the GRIS of two chains but, if pulses of both chains overlap, one GRI is not transmitted at that instant. Furthermore, it will discuss the impact of this blanking on the use of Loran-C signals for transmitting data. A strategy is given for selecting GRIS, based on the presented theory. The paper is based on papers presented at the 1993 WGA technical symposium and the 1993 INA conference.