Ultra-wideband (UWB) ranging radios, an emerging technology that offers precise, short distance range measurements are investigated as a method to augment carrier-phase GPS positioning. A commercially available UWB ranging system is used in a tightly-coupled GPS and UWB real-time kinematic (RTK) system. The performance of the tightly-coupled system is evaluated in static and kinematic testing. This work demonstrates that UWB errors can be successfully estimated in a real-time filter. The results of static testing show that the integrated solution provides better accuracy, better ability to resolve integer ambiguities and enhanced fixed ambiguity solution availability compared with GPS alone. In kinematic testing in a degraded GPS environment, sub-decimetre accuracy was maintained.

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.

Recent work has revealed that increasing numbers of drivers now receive driving instructions using a portable navigation system. A 2×2×2 (position×display decrease mode×voice) factorial experiment was executed to compare driving performance when using a portable navigation system (PNS). Thirty-two subjects were paid to participate in this field study, and a smart phone was adopted as the portable navigation device. The results indicated that drivers using the PNS under the conditions up position and with voice instruction performed better in terms of trip duration, mean speed, and the standard deviation of speed.

Privacy is an increasingly important aspect surrounding the introduction of road pricing in the Netherlands. Different systems for monitoring vehicles result in different consequences for privacy. This contribution describes the privacy aspects in the different scenarios used by the Dutch government. It is often suggested that privacy is a hindrance for road pricing, but if smart choices are made, this does not necessarily have to be the case. In this contribution, we suggest several concrete technological, legal and organizational (partial) solutions, that could be useful in implementing privacy-friendly road pricing.

A number of automated decision support tools will be required in the future air traffic management system to enable continued provision of safe and efficient services in increasingly congested skies. In particular, Conflict Detection and Resolution (CDR) tools should allow for early detection of possible conflicts and propose safe and efficient resolution manoeuvres to avoid loss of separation. However, current approaches in the open literature not only use different levels of aircraft intent information but also make a number of assumptions on models of aircraft motion. Furthermore, information relevant to aircraft performance is often not considered with the consequence of the resulting resolution strategies being potentially unreliable. This paper presents an enhanced, strategic, pairwise, performance-based and distributed CDR algorithm. It accounts for the weaknesses of current approaches by using the maximum level of aircraft intent information together with a novel trajectory prediction model. Numerical results for representative conflict scenarios show that the proposed CDR method is able to generate conflict-free trajectories for participating aircraft while taking into account the actual aircraft capabilities to perform the recommended resolution manoeuvres.

In this paper we assume that we have measurements of a first difference of a typical satellite navigation carrier phase differential, which is a homogeneous quadratic function of the components of the attitude quaternion. We illustrate the determination of large or sustained attitudes using a dedicated unscented Kalman filter. The unscented Kalman filter structure was chosen for the dedicated filter because of its derivative free nature and other advantages. When a Gaussian distributed vector random variable is transformed to an equivalent quaternion it does not continue to be Gaussian distributed. For this reason, a new predictor-corrector form of the unscented Kalman filter is proposed to maintain the normalization of the unscented mean quaternion estimate in the presence of additive disturbances. The results from our realistic simulations indicate that the large attitude of a spacecraft can be estimated to within 0·1% accuracy over large time frames. The filter is particularly useful for autonomous operations of spacecraft as well as in other applications where the process model is bilinear or second order in the states.

Receiver Autonomous Integrity Monitoring (RAIM) is a method, used by an aircraft's receiver, for detecting and isolating faulty satellites of the Global Navigation Satellite System (GNSS). In order for a receiver to be able to detect and isolate a faulty satellite using a RAIM algorithm, a couple of conditions must be met: a minimum number of satellites, and an adequate satellite geometry. Due to the highly predictable orbits of the GPS satellites, a RAIM availability prediction can be done easily. A number of RAIM methods exist; however, none of them takes into account the precise terrain masking of the satellites for the specific location. They consider a uniform fixed mask angle over the whole horizon. This paper will introduce the variable mask RAIM algorithm in order to show to what extent the terrain can affect the RAIM availability and how much it differs from the conventional algorithms.

The purpose of this paper is to analyse the significance of the human element in accidents involving Greek-flagged ships, during 1993–2006, worldwide. In this context, the human element as a general factor of accident initiation and most importantly its constituent components, in the form of specific onboard duties (functions) and/or off-board (mainly ashore) entities, were presented and analysed. It was found that 57·1% of all accidents were attributed to the human element, whereas 75·8% of the latter were detected onboard and 80·4% of the onboard human-induced accidents were linked to errors and violations of the ship's master. Furthermore, since the timeframe examined covers the implementation of the ISM Code, the current analysis was aimed at producing valuable information with regard to its effectiveness upon Greek shipping. In this respect, a 12·2% reduction of human-caused accidents has been found during the post-ISM period. Finally, the association between specific accident types and human element components was examined utilising the technique of correspondence analysis and it was found that groundings and collisions were closely related to the ship's Master, whereas mechanical failures and fires were associated with the engine officers, and cargo shifts and flooding with bridge officers.

Marine traffic survey is a fundamental part of marine traffic engineering. In the assessment of the safety or effectiveness in particular water areas, the distribution of ship tracks is always included as one of the most significant results of a marine traffic survey. In this paper, methods of marine traffic survey are discussed and an appropriate method is selected to obtain the traffic data considering the available research circumstances in China. A semi-automatic artificial way of plotting a distribution diagram of ship tracks is presented with illustrations. Details of the diagram plotted by using the collected traffic data are described for reference.

Navigational safety analysis relying on collision statistics is often hampered because of the low number of observations. A promising alternative approach that overcomes this problem is proposed in this paper. By analyzing critical vessel interactions this approach proactively measures collision risk in port waters. The proposed method is illustrated for quantitative measurement of collision risks in Singapore port fairways, and validated by examining correlations between the measured risks with those perceived by pilots. This method is an ethically appealing alternative to the collision-based analysis for fast, reliable and effective safety assessment, thus possessing great potential for managing collision risks in port waters.

The movement of a land vehicle is constrained because the vehicle always remains on the Earth's surface and only experiences small pitch and roll angles. So the GPS/INS integrated system for land vehicle navigation could be reconfigured to be the integration of GPS and reduced INS to cut down the costs. In a reduced INS, the vertical accelerometer and two horizontal gyros could be omitted from the system. But both theoretical analysis and experimental results show that this configuration may result in the divergence of height solution and large velocity errors. To improve the system performances, precise velocity derived from GPS carrier phase measurements, together with the GPS single point positioning solution, is used to aid the reduced INS. Field test results have demonstrated that first, the aiding from GPS precise velocity overcomes the divergence problem of the integrated height solutions and improves the integrated velocity and secondly the proposed novel integration scheme could achieve comparable navigation accuracy with that from the GPS and full INS integrated system.

When an officer of the watch (OOW) faces complicated marine traffic, a suitable decision support tool could be employed in support of collision avoidance decisions, to reduce the burden and greatly improve the safety of marine traffic. Decisions on routes to avoid collisions could also consider economy as well as safety. Through simulating the biological evolution model, this research adopts the genetic algorithm used in artificial intelligence to find a theoretically safety-critical recommendation for the shortest route of collision avoidance from an economic viewpoint, combining the international regulations for preventing collisions at sea (COLREGS) and the safety domain of a ship. Based on this recommendation, an optimal safe avoidance turning angle, navigation restoration time and navigational restoration angle will also be provided. A Geographic Information System (GIS) will be used as the platform for display and operation. In order to achieve advance notice of alerts and due preparation for collision avoidance, a Vessel Traffic Services (VTS) operator and the OOW can use this system as a reference to assess collision avoidance at present location.

Inspired by Professor Kemp's historical article on the use of soundings in navigation, this contribution provides useful information on the use of leadlines in commercial fishing and the Royal Navy in the mid-20th Century.