Unlike a direct broadcasting satellite navigation system, the transmitting satellite navigation system developed in China uses transponders onboard communication satellites to retransmit navigation signals generated at a ground master station. The transmitting navigation satellite constellation consists of a number of inclined geosynchronous orbit (IGSO) satellites. Considering China's mainland coverage in the northern hemisphere occupies some 62 degrees in longitude, the inclination of the IGSO satellites cannot be too high, or its signals would not be received by the users in the middle and high latitude areas when the IGSO satellite travels over the southern hemisphere. Meanwhile, the latitude of the most southerly station in China mainland that can uplink navigation signals is about 18°N when the IGSO satellite travels to the southern hemisphere. Therefore, there is a need to consider the IGSO inclination to achieve balance between uplinking high-quality navigation signals and covering the high-latitude area. In this work, the navigation performance and availability of the IGSO satellite are examined when navigation signals are uplinked from the stations Lintong and Sanya.

Integrated navigation using multiple Global Navigation Satellite Systems (GNSS) is beneficial to increase the number of observable satellites, alleviate the effects of systematic errors and improve the accuracy of positioning, navigation and timing (PNT). When multiple constellations and multiple frequency measurements are employed, the functional and stochastic models as well as the estimation principle for PNT may be different. Therefore, the commonly used definition of “dilution of precision (DOP)” based on the least squares (LS) estimation and unified functional and stochastic models will be not applicable anymore. In this paper, three types of generalised DOPs are defined. The first type of generalised DOP is based on the error influence function (IF) of pseudo-ranges that reflects the geometry strength of the measurements, error magnitude and the estimation risk criteria. When the least squares estimation is used, the first type of generalised DOP is identical to the one commonly used. In order to define the first type of generalised DOP, an IF of signal–in-space (SIS) errors on the parameter estimates of PNT is derived. The second type of generalised DOP is defined based on the functional model with additional systematic parameters induced by the compatibility and interoperability problems among different GNSS systems. The third type of generalised DOP is defined based on Bayesian estimation in which the a priori information of the model parameters is taken into account. This is suitable for evaluating the precision of kinematic positioning or navigation. Different types of generalised DOPs are suitable for different PNT scenarios and an example for the calculation of these DOPs for multi-GNSS systems including GPS, GLONASS, Compass and Galileo is given. New observation equations of Compass and GLONASS that may contain additional parameters for interoperability are specifically investigated. It shows that if the interoperability of multi-GNSS is not fulfilled, the increased number of satellites will not significantly reduce the generalised DOP value. Furthermore, the outlying measurements will not change the original DOP, but will change the first type of generalised DOP which includes a robust error IF. A priori information of the model parameters will also reduce the DOP.

The LAMBDA method for integer least-squares ambiguity resolution has been widely used in a great variety of Global Navigation Satellite System (GNSS) applications. The popularity of this method stems from its numerical efficiency and its guaranteed optimality in the sense of maximising the success probability of integer ambiguity estimation. In the past two decades, the LAMBDA method has been typically used in cases where the number of ambiguities is less than several tens. With the advent of denser network processing and the availability of multi-frequency, multi-GNSS systems, it is important to understand LAMBDA's performance in high dimensional spaces. In this contribution, we will address this issue using real GPS data based on the Bernese software. We have embedded the LAMBDA method into the Bernese software and compared their ambiguity resolution performances. Twelve day dual-frequency GPS data with a sampling interval of 30 s was used in the experiment, which was collected from a network of 19 stations in the Perth area of Western Australia with an average baseline length of 380 km. Different experimental scenarios were examined and tested with different observation spans, which represent the different ambiguity dimensions. The results showed that LAMBDA is still efficient even when the number of ambiguities is more than 100, and that the baseline repeatability obtained with the ambiguities resolved from the LAMBDA method agreed well with that of Bernese. Therefore, for future dense network processing, the easy-to-use LAMBDA method should be considered as an alternative to baseline-per-baseline methods as those used in e.g. the Bernese software.

Interoperability of GNSS Open Services is a significant trend in the development of all the satellite navigation systems, and its performance will directly affect the users' security and reliability. Therefore, the monitoring and assessment of GNSS Open Services has become a focus of attention for all providers and users of GNSS. In this paper the elements and methods for the monitoring and assessment of GNSS Open Services are investigated first. Then the schemes designed for an international GNSS Monitoring and Assessment System (iGMAS) are proposed. The schemes are based on omni-directional antennas, multi-beam antennas and a high-gain paraboloid antenna to achieve Quadruple-overlap and Single-overlap coverage and sophisticated analysis respectively. Moreover, the scheme for the deployment of world-wide monitoring stations is also proposed. Finally, some related works that have been conducted to monitor and assess Beidou Open Services are introduced, which verifies the feasibility of the proposed system.

The evaluation of Beidou system time is one of the important tasks in constructing and developing the Beidou satellite navigation system. The evaluation methods based on two-way satellite time and frequency transfer method (TWSTFT) and GPS common-view method are proposed in this paper. Tests and performance evaluation of the Beidou time system (BDT) were conducted. Results show that BDT is stable and reliable. The BDT frequency deviation, Allan deviations and clock offsets, relative to UTC (NTSC), are 10e-14, 10e-15 and less than 30 ns respectively.

The estimation of GPS repeater jamming plays an important role in modern military applications. In this paper, based on the maximum likelihood estimation (MLE) method, a new approach for the estimation of GPS repeater jamming using Kalman filtering with coloured observation noise is proposed. The state equation and observation equation of the Kalman filter with the coloured observation noise are deduced and the generation process explained. The recursive formula for the Kalman filter used to iteratively filter for the MLE output is also derived. Experimental results show that the new design has a better performance than the MLE; hence it can be used for the precise estimation of repeater jamming signals under the condition that the carrier-to-noise density ratio is below 20 dB-Hz.

In this contribution, a novel un-differenced (UD) (PPP-RTK) concept, i.e. a synthesis of Precise Point Positioning and Network-based Real-Time Kinematic concept, is introduced. In the first step of our PPP-RTK approach, the UD GNSS observations from a regional reference network are processed based upon re-parameterised observation equations, corrections for satellite clocks, phase biases and (interpolated) atmospheric delays are calculated and provided to users. In the second step, these network-based corrections are used at the user site to restore the integer nature of his UD phase ambiguities, which makes rapid and high accuracy user positioning possible. The proposed PPP-RTK approach was tested using two GPS CORS networks with inter-station distances ranging from 60 to 100 km. The first test network is the northern China CORS network and the second is the Australian Perth CORS network. In the test of the first network, a dual-frequency PPP-RTK user receiver was used, while in the test of the second network, a low-cost, single-frequency PPP-RTK user receiver was used. The performance of fast ambiguity resolution and the high accuracy positioning of the PPP-RTK results are demonstrated.

A major disadvantage of nearly every marine electronic navigation device introduced to date is the necessity for the navigator to turn his or her attention away from the view outside the bridge windows, even momentarily. Indeed, the uncomfortable feeling experienced by seasoned mariners that this ‘head down’ posture creates has led many to be initially reluctant to adopt some marine electronic devices (radar, ARPA, ECDIS, to name a few) that have proven their worth over time as useful, even vital navigational aids. Unfortunately, the use of such equipment has always required the marine navigator to leave behind the real world perspective view and enter an unnatural, two-dimensional plan view of the area surrounding the vessel. Mariners have accepted this type of view by necessity rather than by choice. That may be about to change. Advances in technology and a proven track record of performance benefits from Head-Up Display (or HUD) information in the aviation field have made it possible to consider if such a device would be useful in a maritime context. Accordingly, the authors of this paper conducted a preliminary evaluation to examine empirically what the effects of providing this same type of head-up information would be on marine navigation performance. A series of tests were conducted in the California Maritime Academy's advanced simulation facilities utilizing a full-mission simulator, a laptop-based HUD prototype, a projector, and student participants from an experimental undergraduate course entitled e-Navigation. The goals were to: 1) define the operational requirements and concept of operations for a maritime HUD system; 2) identify essential information, risks, and concerns; and 3) examine performance variations by conditions (environmental, vessel, crew) and tasks. The results indicate great potential for a maritime HUD system, especially for improving situational awareness in low visibility conditions, confined waters, and for vessels where information changes rapidly (i.e., high speed vessels). The results also suggest that there are some standard information requirements across situations that could be augmented with task and vessel specific information.

The benefits of Global Navigation Satellite Systems (GNSS) and in particular GPS have been demonstrated worldwide, and continue to accrue in the form of new applications. Today, some mission critical applications (largely driven by safety) mostly in aviation and to a lesser extent maritime, rely on a number of techniques for the provision of integrity monitoring services. However, for many applications such as those associated with the emergency services, road user charging and personal navigation devices, no such monitoring exists and service validation is limited due to technical and cost constraints. The problem is exacerbated by a recent increase in more challenging problems, particularly in the security industry, in which jamming devices have been used to disrupt the use of GPS. This paper presents a new approach for a cost effective local solution to the problems above, at the individual user level, by providing the user with information on Quality of Service (QoS). The approach is based on the deployment of a single or network of probes supported by an existing regional network. The probes communicate with a central server and are designed to detect localised events whilst the regional network isolates space segment anomalies. The latter is addressed in detail in this paper in terms of design methodology and performance, using the Ordnance Survey's UK GNSS network.

The Automatic Identification System (AIS) is now well established and widely used in commercial shipping. The system originated from a safety mandate but AIS messages have also been shown to be useful from a security situational awareness perspective. In terms of coastal security, AIS messages are often received by land-based receivers positioned along a nation's coastline. The operational range of the receivers is controlled by complex variable VHF propagation characteristics, power of the transmitter, etc. However, certain characteristics of the reception coverage area can be determined from the AIS message receptions themselves. This paper presents an algorithm to compute coverage characteristics using AIS messages. The algorithm is applied to synthetic data with known coverage characteristics, and also real AIS data obtained from the Maritime Safety and Security Information System. Results from the Norwegian, North and Baltic Seas show how the coverage estimate is influenced by the coverage edge, lack of vessel activity, and diversity in the source data.

Current strategic plans for Air Traffic Management (ATM) envisage a transition from radar control to a trajectory-based system. Part 1 sketched the historical origins of separation minima and then analysed the safety thinking behind current minima and the issues involved in risk modelling. Part 2 examines the future situation. This focuses on the intermediate steps to the final system – upgraded capabilities in a mixed-equipage system. Future traffic mixes two categories of traffic: V aircraft, i.e. vectored traditional ATC-handled, and 4D aircraft, i.e. flying on 4D trajectories. Conflict probe and other decision support tools will need to be in place, inter alia to prevent controller workload from increasing. Conceptually, future risks in the transition period will be the sum of three types of aircraft encounter risk: V/V, 4D/4D and 4D/V. These pose different kinds of problem for ATC, appropriate conflict alerting systems and risk assessment. The numbers of 4D/V encounters increase rapidly with growth in the proportion of 4D aircraft. With reduced minima, airborne collision avoidance systems would be unlikely to resolve higher relative velocity encounters were the ATC system to fail. It would be a difficult decision to reduce markedly ATC separation minima for any category of aircraft encounters during the transition period.

In the maritime community, a runner-up will undertake this typical process to catch up with the front runner; first, as a nation's economy grows its domestic crew costs rise, creating a gap with those abroad, which in turn depresses the international competitiveness of shipping companies. Then, to maintain their economic strength, shipping companies have their ships fly a “flag of convenience” relying on increasing amounts of cheap foreign labour. As a result, the nation gradually loses domestic seafarers, which, in the worst case, leads to a depletion of national human resource needed for its maritime cluster to continue to exist. In that sense, the personnel shortage issue is a fate for top runners in the marine transport world, where international competitiveness is inevitable. The Japanese maritime sector is just facing this issue. In this paper, the current situation in the maritime sector and its dependence on foreign labour, the cause and process of the change and the problems of the outcomes are explained, and the possible solutions in terms of the social mechanism of personnel development and utilization are discussed.

We present a method for addressing probabilistic queries about the location of a vessel in the time interval between two position reports, such as from the Automatic Identification System (AIS). The heart of the method is the random generation of physically feasible paths connecting the two reports. The method empowers operators to answer probabilistic questions about any characteristic of the unknown true path. For illustrative purposes, we demonstrate the use of the method to identify which of several vessels is the most likely perpetrator, in a fictitious scenario in which illegal dumping of waste matter has taken place.

We present an approximation method for geodesic circles on a spheroid. Our ap­proximation curve is the intersection of two spheroids whose axes are parallel, and it interpolates four points of the geodesic circle. Our approximation method has two merits. One is that the approximation curve can be obtained algebraically, and the other is that the approximation error is very small. For example, our approximation of a circle of radius 1000 km on the Earth has error 1·13 cm or less. We analyze the error of our approximation using the Hausdorff distance and confirm it by a geodesic distance computation.

Future air navigation envisages increased use of Global Navigation Satellite Systems (GNSS) together with advanced communications and surveillance technologies to facilitate the required increase in capacity, efficiency and safety without adversely impacting the environment. The full benefit of GNSS is expected from its ability to support en-route to en-route or gate-to-gate air navigation. This presents challenges particularly for the phases of flight with stringent required navigation performance. Significant work has so far been devoted to the phases of flight up to CAT I. However, more work is required for CAT III precision landing (with an accuracy requirement at the metre level) and taxiing (with an accuracy requirement at sub-metre level) and both with very high integrity and continuity requirements. The main limitation in using GBAS for CAT III landings is the potential decorrelation of the measurement errors between the GBAS ground station (GGS) and the user. The threats in this respect are the atmospheric anomalies. Periods of strong solar activity can cause large local spatial and temporal gradients in the delays induced on the GNSS signals by the ionosphere. The local nature of the effects results in significant decorrelation between GGS measurements and the user. Therefore, a reliable ground based ionospheric anomaly monitoring scheme is required to guarantee integrity.

This paper critically reviews state-of-the-art monitors, identifies their limitations and addresses them by proposing a high-performance monitoring scheme for the ionosphere. Preliminary analyses suggest that the proposed scheme has the potential to enable GNSS to meet the navigation requirements for CAT III and taxiing.

Modern attitude and heading reference systems (AHRS) generally use Kalman filters to integrate gyros with some other augmenting sensors, such as accelerometers and magnetometers, to provide a long term stable orientation solution. The construction of the Kalman filter for the AHRS is flexible, while the general options are the methods based on quaternion, Euler angles, or Euler angle errors. But the quaternion and Euler angle based methods need to model system angular motions, and, meanwhile, all these three methods suffer from nonlinear problems which will increase the system complexities and the computational difficulties. This paper proposes a novel implementation method for the AHRS integrating IMU and magnetometer sensors. In the proposed method, the Kalman filtering is implemented to use the Euler angle errors to express the local level frame (l frame) errors, rather than express the body frame (b frame) errors as the customary methods do. A linear system error model based on the Euler angles errors expressing the l frame errors for the AHRS has been developed and the corresponding system observation model has been derived. This proposed method for AHRS does not need to model system angular motions and also avoids the nonlinear problem which is inherent in the commonly used methods. The experimental results show that the proposed method is a promising alternative for the AHRS.

In this study, an experiment to establish a model for human-environment social systems, a multi-agent simulation model to deal with urban traffic congestion problems involving automobiles embedded with several strategies of car navigation systems (CNS), is presented. A shortest time route with route information sharing strategy (ST-RIS) is believed to be one of the solutions for a novel CNS based on bilateral information shared among automobile agents. We assume several strategies including ST-RIS for agents, which are defined differently in terms of their information-handling process. The question of which strategy is most appropriate for solving urban traffic congestion can be seen as a social dilemma, because social holistic utility may conflict with an agent's individual utility. The presented model shows that this social dilemma can be observed as a typical chicken-type dilemma, or as a typical minority game, where an agent who has adopted a minority strategy can earn more utility compared to when other strategies are used. Consequently, the model has illustrated that shortest time route with partial route information sharing strategy (ST-pRIS), which is an advanced strategic form of ST-RIS in which only partial information is shared among agents, has moderate potential to be diffused in a society from the viewpoint of the evolutionary game theory.