The last few years have seen a rapid growth of applications based on positioning information provided by satellite positioning systems. In transport management and control, satellite positioning has proven to be the most promising means for spatial location data collection. With the GPS modernisation programme well underway, and the recent developments of the Galileo project, even more GNSS-based applications are to be expected in the future. One such GNSS-based application is the use of position and velocity information as the prime input to a road user charging (RUC) scheme. However, navigation in urban environments raises a number of problems. Most important are the difficulties related to signal obstruction by features such as tall buildings, urban canyons, bridges and trees, as well as the effects of multipath caused by signal reflections from buildings and other vehicles. Given the inevitable limitations of road trials, the use of simulation modelling to assess the present and future satellite positioning systems' performance to support urban RUC seems indispensable. The main objective of the research undertaken at the University of Nottingham Institute of Engineering Surveying and Space Geodesy (IESSG), and the Nottingham Centre for Infrastructure (NCI), was to develop a tool to simulate GPS for Satellite Positioning-based Road User Charging (SPRUC). In this regard, an existing GPS simulator was modified to rectify one of its major weaknesses, namely the inability to address properly the change in non-static GPS measurements with respect to changes in built environment. For this purpose, state-of-the-art Geographic Information Systems (GIS) software was used to complement the simulator, and consequently a seamless interface between the two software has been developed. Finally, in order to provide a prime input to the simulator, field tests have been undertaken and significant amounts of GPS data were collected. Statistics were also derived for positioning accuracy and signal availability so that the results from the simulation modelling can be validated against those from the undertaken road trials.

Fast high precision relative Global Navigation Satellite System (GNSS) positioning is very important to various applications and ambiguity resolution is a key requirement. It has been a continuing challenge to determine and fix GNSS carrier-phase ambiguity, especially for medium- and long-distance baselines. In past research, with dual-frequency band Global Positioning System (GPS), it is almost impossible for fast ambiguity resolution of medium- and long-distance baselines mainly due to the ionospheric and tropospheric effects. With the launch of the BeiDou system, triple-frequency band GNSS observations are available for the first time. This research aims to test the ambiguity resolution performance with BeiDou triple-frequency band observations. In this research, two mathematical models are compared: zenith tropospheric delay as an unknown parameter versus corrected tropospheric delay. The ambiguity resolution performance is investigated in detail with BeiDou observations. Different distance baselines are tested: 45 km, 70 km and 100 km and the performances are investigated with different elevation cut-off angles. Also the performance with BeiDou alone and combined BeiDou and GPS are compared. Experimental results clearly show that with practical observations of triple-frequency bands, ambiguity of medium- or long-distance baselines can be fixed. The results also show that: the performance of ambiguity resolution with an elevation cutoff angle of 20° is much better than that of 15°; The performance with tropospheric effect corrected is slightly better than that with tropospheric effect as an estimated parameter; Dual-frequency band GPS observations will benefit ambiguity resolution of integrated BeiDou and GPS.

This paper proposes a computation method for the determination of the worst user location (WUL) instead of the current grid search-based methods. The WUL is a key parameter in the estimation of the Galileo integrity data. Since a satellite clock error is the same for all users whereas the orbital error is different depending on the location of users, the WUL depends on the satellite orbit errors which can be estimated using the measurements from the Galileo sensor stations. The proposed algorithm uses the resolved orbital errors to calculate an approximate WUL on a spherical model of the Earth. The next step is to determine the WUL on a specified ellipsoid model using an iterative transformation process. Results show that the proposed method is more accurate and computationally efficient than the current search-based methods. The computation time required is minimal making it valuable in meeting the real time requirements for the generation of the Galileo integrity flag.

The discussion following Captain C. V. Sølver's claim to have discovered an early Norse bearing-dial incidentally raised the question of what was the ‘dyoll’ referred to in English ship inventories of the fifteenth century. There are various practical reasons for doubting the theory that it was a compass-dial, that is to say a sun-dial with an inset compass, which for a particular latitude would, when correctly orientated, indicate the time of day. However, the idea that the ‘dyoll’ indicated time rather than direction seems to fit the evidence, and G. P. B. Naish's note on fifteenth- to seventeenth-century ship inventories leaves little doubt that it was an instrument for measuring equal intervals of time, and probably a sand-glass. This conclusion, which to some extent casts the early history of the compass card once more into the melting-pot, prompts a number of questions. Some are stated here and are answered either wholly or in part. Others remain to be answered.

The technique of tracking a non-cooperative manoeuvring satellite is important for Space Situation Awareness (SSA). However, the classical extended Kalman filter cannot work successfully in this situation. Motivated by this problem, a novel Extended Kalman Filter with Input Detection and Estimation (EKF/IDE) method is proposed in this paper for tracking a non-cooperative satellite with impulsive manoeuvres. The impulsive manoeuvre is modelled as an unknown acceleration without any prior information. An unbiased minimum-variance input and state estimation method is introduced to estimate the manoeuvre acceleration. An approach based on the Mahalanobis distance of the manoeuvre estimate error is proposed for manoeuvre detection. With the impulsive manoeuvre being detected and estimated accurately, an adaptive extended Kalman filter is proposed to estimate the state of the target. An approach of covariance inflation is proposed to deal with the manoeuvre during the unobserved period. Simulations and Monte Carlo experiments are implemented to demonstrate the feasibility and validity of the proposed method. The results of simulations show that the proposed method can accurately detect and estimate unknown impulsive manoeuvres of a non-cooperative satellite. Through the compensation of the estimated manoeuvre, the estimation of position and velocity after the manoeuvre maintains the accuracy of the pre-manoeuvre period, demonstrating the robustness of the proposed method against unknown manoeuvres.

Although AIS is already in use in a range of vessels, there has been little public discussion on how AIS should interact with the COLREGS in practice. The objective of this paper is to make a contribution to that debate, while recognising that “best practice” will evolve as more practical experience is obtained. The paper suggests the approach that should be adopted in several areas, but concludes that, overall, AIS is nothing more than one of several tools that should enable mariners to fulfil their existing obligations under the COLREGS.

The Right Whale Sighting Advisory System (RWSAS) is a National Oceanic and Atmospheric Administration (NOAA) Fisheries program designed to reduce collisions between vessels and critically endangered North Atlantic right whales. The vessel speed restriction that is part of the RWSAS presents navigation stakeholders with numerous challenges, owing to concerns about increased risks of ship grounding and collisions within ports. In this paper, we present a multi-methodology framework for assessing the impact of the vessel speed restriction on navigational safety. Empirically, we base our discussion in a first-order analysis of ship grounding risk for the Charleston Entrance Channel. Our analysis proceeds in three parts. We begin by using fault and event tree analyses to assess a relevant set of grounding-related event progression and failure probabilities. The influence of alternative vessel speed restrictions on ship grounding risk are then explored via a Bayesian network model that utilises the previously specified fault and event tree models for its partial specification and enumeration. Our analysis suggests that the speed restriction can, under certain reasonable assumptions, be seen to adversely impact the risk of ship grounding accidents in the Charleston Entrance Channel. We conclude with a summary of our findings and recommendations for future research.

Multipath arises from the reception of reflected or diffracted signals in addition to the Line-Of-Sight (LOS) signal. By using a block processing high sensitivity receiver scheme, this paper aims to obtain better positioning performance in urban canyon areas. Generally, the peak with the most power is utilised in high sensitivity receivers; however, this approach is not always optimal in multipath environments. Noting that signal correlation peaks may be separated in the Doppler domain by a long coherent integration time, a peak identification scheme is proposed in this work, which yields better positioning performance. It is shown that most of the multipath peaks are removed in the receiver after using the proposed algorithm.

Separation standards are used for assuring the safe and effective operation of aircraft in a traffic control environment and as aircraft operations increase in number the need to reconsider separation standards is strongly voiced both by operators and controllers. A panel, the Review of the General Concept of Separation Panel (RGCSP), has been organized by ICAO and the possibility of reducing conventional separation standards has been discussed. Mathematical models for estimating collision risk due to loss of separation between aircraft require data on navigation accuracy. In general, three-dimensional radars are used for height finding but these are complicated and expensive.

The altitude of the cruising aircraft is required within about 100 ft. In the simplified radar here described a rotating antenna produces a fan beam for scanning aircraft flying overhead. The data obtained from several scans are processed by a mini-computer and the height of the aircraft estimated by a least-square method and sequential approximation. Between the items of information obtained for each scan (the distance, the elevation angle and the data acquisition time) a theoretical relationship is established as an observation equation, one of the coefficients of which includes the height information. The coefficient is determined by a curve-fitting method. The paper first describes the method of analysis for height estimation and then an evaluation of the accuracy of the method by a computer simulation.

Methods of calculating the course and the distance between two points from a knowledge of their latitudes and longitudes, or calculating the latitude and the longitude of the arrival point from the course and the distance from a known departure point, are called sailings. Middle-latitude sailing and Mercator sailing have been widely used.

The paper presents the error characteristics of a vehicle dynamic model (VDM)-based integration architecture for fixed-wing unmanned aerial vehicles. Global navigation satellite system (GNSS) and inertial measurement unit measurements are fused in an extended Kalman filter (EKF) which uses the VDM as the main process model. Control inputs from the autopilot system are used to drive the navigation solution. Using a predefined trajectory with segments of both high and low dynamics and a variable wind profile, Monte Carlo simulations reveal a degrading performance in varying periods of GNSS outage lasting 10 s, 20 s, 30 s, 60 s and 90 s, respectively. These are followed by periods of re-acquisition where the navigation solution recovers. With a GNSS outage lasting less than 60 s, the position error gradually grows to a maximum of 8⋅4 m while attitude errors in roll and pitch remain bounded, as opposed to an inertial navigation system (INS)/GNSS approach in which the navigation solution degrades rapidly. The model-based approach shows improved navigation performance even with parameter uncertainties over a conventional INS/GNSS integration approach.

When a collision occurs between two ships on the high seas, very likely one may need to determine who should be liable for the collision and the apportionment of liability between them. However, it is not unusual to see a collision between an anchored vessel and another vessel underway. When determining apportionment of liability between them, it seems that there is a presumption of fault against the vessel underway. To counteract such a presumption, the author discusses some issues in respect of collisions between a vessel at anchor and others underway under the International Regulations for Preventing Collisions at Sea, 1972 (COLREGs) by examining the obligations of anchored vessels to avoid a collision at sea.

The aim of this study is to provide a balanced distribution of air traffic controller workload (ATCW) across airspace sectors taking into account the complexity of airspace sectors and the factors affecting ATCW, both objective and perceived. Almost all the studies focusing on the airspace sectorisation problem use heuristic or metaheuristic algorithms in dynamic simulation environments instead of a mathematical modelling approach. The paper proposes a multi-objective mixed integer mathematical model for airspace sectorisation. The model is applied to the upper, en-route level of Turkish airspace. Geographical information systems (GIS) are used to advantage for airspace analysis. The multi-objective model developed in this paper is scalarised by using the conic scalarisation method. For solving the scalarised problem, the CPLEX and DICOPT solvers of GAMS software are implemented. Finally, the optimal sector boundaries of Turkish airspace are defined.

In this paper the Grid correction method (GRID) was proposed for the first time as an interpolation method of the double differenced ionospheric delay for GNSS Network RTK. The Distance Interpolation Method (DIM), Linear Interpolation Method (LIM), the Kriging Interpolation Method (KRG) and the GRID are described and compared in the aspect of their interpolation performance. It was shown in the tests that the GRID interpolation method performed better than the other three. For mid-latitude stations, its interpolation accuracy is better than 1 cm, and the extrapolation accuracy is better than 2 cm. Furthermore, the GRID method can achieve a good performance even at low satellite elevation, and also its interpolation accuracy can be better than 2 cm at low latitudes.

The integration of Precise Point Positioning (PPP) with Inertial Navigation Systems (INS) has been very intensively developed and widely applied in multiple areas. The integrated navigation system is able to provide high accuracy position and attitude with a single receiver. However, the cycle slip caused by high dynamics, signal lock and low satellite elevation will decrease accuracy and degrade the system performance. In this paper, an inertial aided cycle slip detection and repair method is applied in PPP/INS tightly coupled navigation to obtain higher accuracy navigation information. The inertial information is introduced to the wide-lane combination observation to avoid the noise and multipath from pseudorange. Detail error analysis is given to determine the critical value of INS position accuracy which makes inertial aided wide-lane combination have better performance and a new decision variable is constructed. The inertial aided cycle slip detection and repair scheme that replaces the ambiguity re-initialisation is applied in PPP. An experiment was performed to validate the new algorithm. The results indicate that the inertial aided decision variable has higher accuracy than the traditional Melbourne-Wübbena decision variable. The inertial aided scheme can efficiently detect and repair the small cycle slip (from 1 to 6) and large cycle slip (from 10 to 20). The inertial-aided cycle slip detection method introduced in PPP resolution will remove the error by ambiguity re-initialisation.

Location and navigation services based on global navigation satellite systems (GNSS) are needed for real-time high-precision positioning applications in relevant economic sectors, such as precision agriculture, transport, civil engineering or mapping. Real-time navigation users of GNSS networks have significantly increased all around the world, since the 1990s, and usage has exceeded initial expectations. Therefore, if the evolution of GNSS network users is monitored, the dynamics of market segments can be studied. The implementation of this hypothesis requires the treatment of big volumes of navigation data over several years and the continuous monitoring of customers. This paper is focused on the management of massive connection of GNSS users in an efficient way, in order to obtain analysis and statistics. Big data architecture and data analyses based on data mining algorithms have been implemented as the best way to approach the hypothesis. Results demonstrate the dynamic of users of different market segments, the increasing demand over the years and, specifically, conclusions are obtained about the trends, year-on-year correlation and business volume recovering after economic crisis periods.

Weather-related ship loss statistics are assessed as a proportion of total losses to ascertain the requirement for route planning. A routeing assessment for suitability of on-board application is undertaken and a moveable grid is then proposed incorporating a time optimization procedure for the on-board system.

The design of new rules on seaways, such as traffic restrictions, requires determining the degree of improvement in marine traffic safety beforehand by considering the occurrence of new hazardous factors. This study proposes a method to predict the future traffic behaviour and ship encounter frequency (EF) with the introduction of a new traffic rule. First, a sensitivity analysis is conducted to identify the factors affecting the EF. A method of predicting future traffic behaviour and EF is presented based on the analysis of changes in the traffic flow in an area with a temporal restriction. Results show that the method appropriately predicts the location and degree of the occurrence of encounters in the sea area. The proposed method contributes to the discussion of future traffic safety, when sailing in a specific area is restricted by new regulations, installations of new offshore wind farms and fishing reefs.

The high-precision global navigation satellite system (GNSS) positioning technique on smartphones has been attracting increasing interest in recent years. However, the low-cost GNSS chip and linearly polarised antenna embedded inside smartphones result in data lack and quality degradation, which hinders the high-precision GNSS positioning on smartphones. In this study, a mixed single- and dual-frequency quad-constellation precise point positioning (MSDQ-PPP) model is proposed to improve the positioning performance on smartphones by taking advantage of all available GNSS observations. Static and kinematic tests were made using a Xiaomi Mi8 smartphone to fully assess the MSDQ-PPP performance with comparisons to single-frequency PPP (SF-PPP) and dual-frequency PPP (DF-PPP) models. The static test results show that the MSDQ-PPP can reach an accuracy level of 0⋅39 m and 0⋅50 m in the horizontal and vertical directions with a convergence time of less than 10 min in most sessions. The MSDQ-PPP improves the positioning accuracy by 53% and 31% over the DF-PPP in the horizontal and vertical directions, respectively. In contrast to the SF-PPP, the positioning accuracy and convergence time improvement can reach 62% and 90% in the horizontal direction, respectively. In the kinematic test, the MSDQ-PPP achieves an accuracy of 0⋅7 m and 1⋅5 m in the horizontal and vertical directions, respectively. The accuracy improvement rates reach 78% and 76% over the DF-PPP, and 13% and 38% over the SF-PPP, respectively. Both static and kinematic MSDQ-PPP tests indicate significantly enhanced positioning performance.

The weak GPS signal-processing work described here was part of the development of an innovative GPS tag – TrackTag™. The technology is aimed at animal tagging applications and therefore has particular challenges. These primarily relate to designing a tag to be small enough in physical size and weight so as not to impact the behaviour of the animal under study as well as robust enough to operate wherever the animal goes. TrackTag's architecture differs from that of a conventional GPS receiver. The key differences are that very short (typically 24 ms) snapshots are used and there is no processing intelligence on the tag itself. Such a short length of ON time, with no need for longer warm or cold starts, results in very little energy being used. This, in turn, allows the design of the tag to be made very small with a minimal battery size requirement and capable of being used over far greater periods than conventional GPS tags. Processing of the data is done on a PC following the download of the tag's memory.

The GPS signal-processing using such short snapshots must not compromise the accuracy of the positions calculated and they should be comparable or better than normal GPS receivers. Weak signal processing is also a requirement for tracking signals in harsh environments involved with tagging animals in their natural habitat. This research has demonstrated that weak-signal processing coupled with the short snapshots, and careful integration of a suitable antenna, allows tracking under rainforest canopy and marine environments. Conventional GPS tends not to work well under those conditions.