Efficient and precise geolocation can be achieved by integrating a ranging system, such as GPS, with inertial sensors in order to bridge short outages, enhance accuracy degradation, and increase the temporal resolution in the ranging system. Optimal integration depends on appropriate filter methods that can accommodate the particular short-term dynamics experienced by platforms, such as UXO ground-based detection systems. The traditional extended Kalman filter was designed to integrate data from a linearized system excited by Gaussian noise. We compared this filter to modern filters that obviate these prerequisites, including the unscented Kalman filter, the particle filter, and adaptive variations thereof, using simulated IMU/ranging systems that follow a typical trajectory with both straight and curved segments. The unscented filter performed significantly better than the extended Kalman filter, particularly over the curved segments, yielding up to 50% improvement in the position accuracy using medium-grade inertial measurement units. Similar improvement was obtained for the unscented particle filter, and its adaptive variant, over the unscented Kalman filter (which performed comparably to the extended Kalman filter) when the statistical distribution of the IMU noise was non-symmetric (i.e., essentially non-Gaussian). While the few-centimetre geolocation accuracy goal for highly dynamic UXO characterization applications remains a challenge if tactical grade IMUs are integrated with a significantly degraded ranging system, using filters appropriate to the inherent nonlinear dynamics and potential non-Gaussian nature of the sensor noise tend to reduce overall errors compared to the traditional filter.

Application of map-matching techniques to GPS positions can provide accurate vehicle location information in challenging situations. The Hidden Markov Model (HMM) is a statistical model that is well known for providing solutions to temporal recognition applications such as text and speech recognition. This paper introduces a novel map-matching algorithm based on HMM for GPS-based wheelchair navigation. Given GPS positions, a hidden Markov chain model is established by using both geometric data and the topology of sidewalk segments. The map-matching algorithm employs the Viterbi algorithm to estimate correct sidewalk segments as hidden states in a HMM in order to match GPS trajectory on the corresponding segment sequence. The HMM-based map-matching algorithm was validated on a campus sidewalk network for wheelchair navigation. The results show an improvement in tracking a wheelchair in dense urban conditions both in accuracy and in computational time.

This paper describes the verification of a real-time attitude determination algorithm during GPS attitude receiver hardware development. The GPS attitude receiver of 24 channels had been already developed in Surrey University. However 24 channels were not enough for practical usage. For this reason, a 48-channel attitude receiver with 12 channels for each antenna has been developed. To estimate attitude in real time, precise relative positions of the GPS antenna array have to be determined as rapidly as possible. However, the calculation load based on the conventional algorithm is too burdensome to perform using the RISC microprocessor. Therefore, in this paper, the cycle ambiguities of each base vector are resolved using SNUGLAD (Seoul Nat Univ GNSS Lab Attitude Determination), the design focus of which is to allow the receiver to estimate the 10 Hz onboard solutions. To keep precise solutions continuously, after ambiguity removal, cycle slip must be detected or isolated. Otherwise, the receiver would output erroneous solutions after a short signal blockage or fading of the GPS signal. To prevent this, we defined the cycle slip detection and repair scheme using a standard extended Kalman filter, which can detect and repair cycle slip within one cycle. As a result, this paper shows that time synchronized measurement with good quality and a reliable solution can be provided by the hardware developed with inexpensive chipsets and that this may be a possible cost efficient sensor for UAV or microsatellites.

This year celebrates the 90th anniversary of the historic first Atlantic crossing by Alcock and Brown in their Vickers aircraft. This paper draws on the log, chart, notes and equipment held in the RAF Museum at Hendon and Sir Arthur Brown's own words to tell the story of the crossing.

This study of Columbus' navigation is unique because it was written by an historian who is also a trained and experienced professional global (and ocean) navigator, rather than an academic historian with only superficial knowledge of the science of navigation as practiced by Columbus and other early navigators. The study is also unique in that as an American historian author disagrees with his colleagues in the USA who present the “politically correct” view of Columbus as an unskilled entrepreneur who obtained his limited knowledge of navigation as a crew member or passenger on Portuguese voyages, rather than as one of the most skilled and experienced of the cadre of respected Genoese captains and navigators used by kings throughout Europe to perform their maritime enterprises.

Remote, or shore-based, pilotage is an issue of some interest to the maritime community. When discussed, it is often in the context of new technology that in one way or the other is supposed to enhance piloting and enable ships to be piloted from the shore. This paper takes a different approach and instead looks at piloting as control of a complex system. Such an approach makes it possible to identify a fundamental problem with remote pilotage. The problem, along with possible solutions, is presented and discussed.

This paper traces the birth and formation of Vessel Traffic Services, examines the rapid growth of such schemes worldwide and notes the tendency for mandatory ship reporting systems to be operated from VTS centres. Questions are asked about this tendency and thoughts are provided.

The January 2009 issue of the Journal of Navigation included a paper (John Wilde Crosbie 2009) entitled, “Revisiting the lessons of the early steering and sailing rules for an e-navigation age.” Following a description of the development of the COLREGS from the early 19th century, he concluded that the current steering and sailing rules should be replaced by a single rule more suited to modern conditions. This might take the form of a rule stating that a vessel taking action to avoid collision should not pass ahead of the other vessel. Such a rule would require a radical change in the philosophy of collision avoidance at sea, and evidence is required that it would be both effective and acceptable by mariners. Radar simulator experiments, conducted by the author some years ago in another context, suggest that this might be the case. An analysis of the experimental results and some conclusions are reported in this paper. The author recommends that further trials, specifically designed to test the Crosbie proposals, would be desirable.

Efficient marine navigation through obstructions is still one of the many problems faced by the mariner. Many accidents can be traced to human error, recently increased traffic densities and the average cruise speed of ships impedes the collision avoidance decision making process further in the sense that decisions have to be made in reduced time. It seems logical that the decision making process be computerised and automated as a step forward to reduce the risk of collision. This article reviews the development of collision avoidance techniques and path planning for ships, particularly when engaged in close range encounters. In addition, previously published works have been categorised and their shortcomings highlighted in order to identify the ‘state of the art’ and issues in close range marine navigation.

It is well known that vessels operating in the vicinity of a lateral bank experience a significant yaw moment and sway force. This bank effect has a major impact on the manoeuvring properties of the vessel and must therefore be properly understood to ensure the safe passage of the vessel through the restricted waterway. Accordingly, this study performs a series of simulations using commercial FLOW-3D® computational fluid dynamics (CFD) software and the KRISO 3600 TEU container ship model to examine the effects of the vessel speed and distance to bank on the magnitude and time-based variation of the yaw angle and sway force. The results show that for a given vessel speed, the yaw angle and sway force increase as the distance to bank reduces, while for a given distance between the ship and the bank, the yaw angle and sway force increase with an increasing vessel speed. In addition, it is shown that even when a vessel advances at a very low speed, it experiences a significant bank effect when operating in close vicinity to the bank. Overall, the results presented in this study confirm the feasibility of the CFD modelling approach as a means of obtaining detailed insights into the bank effect without the need for time-consuming and expensive ship trials.

An analytical method and algorithm for great elliptic sailing (GES) calculations is presented. The method solves the complete GES problem calculating not only the great elliptic arc distance, but also other elements of the sailing such as the geodetic coordinates of intermediate points along the great elliptic arc. The proposed formulas provide extremely high accuracies and are straightforward to be exploited immediately in the development of navigational software, without the requirement to use advanced numerical methods. Their validity and effectiveness have been verified with numerical tests and comparisons to extremely accurate geodetic methods for the direct and inverse geodetic problem.

This contribution extends the common documented approach of integrity through Protection Levels in Satellite-Based Augmentation System (SBAS) positioning for aeronautics, to reliability on the basis of statistical hypothesis testing, and as such provides a safeguard against model misspecifications as anomalies and outliers in the measurements. It is shown that when integrity is monitored through Protection Levels and reliability added through Reliability Levels, the availability of the SBAS position solution is more than 99% for APV-I precision approach. The availability for CAT-I is currently just a few percent. When the Galileo constellation is added, and current performance is copied ahead, the percentage for CAT-I increases to beyond 95%.

Multipath is one of the main error sources in global navigation satellite system (GNSS) positioning. The high-resolution correlator (HRC) is a multipath mitigation technique well known for its outstanding performance for mid-delayed multipath, but still has a remaining error for the short-delayed multipath. This paper proposes a modified HRC scheme that can remove or reduce the error for short-delayed multipath signals. It estimates the HRC tracking error and augments the conventional HRC with the estimates. The method was implemented with a software receiver and the test results show short-delayed multipath-induced errors were reduced to about one third of those from the conventional HRC.

Ionospheric delay is the major source of satellite positioning system performance degradation. Designers of satellite positioning systems attempt to mitigate the impact of the ionospheric delay by deployment of correction models. For instance, the American GPS utilises a global standard (Klobuchar) model, based on the assumption that the daily distribution of GPS ionospheric delay values follows a biased cosine curve during day-time, while during the night-time the GPS ionospheric delay remains constant. Providing a compromise between computational complexity and accuracy, the Klobuchar model is capable of correcting up to 70% of actual ionospheric delay, mainly during quiet space weather conditions. Unfortunately, it provides a very poor performance during severe space weather, geomagnetic and ionospheric disturbances. In addition, a global approach in Klobuchar model development did not take into account particularities of the local ionospheric conditions that can significantly contribute to the general GPS ionospheric delay. Current research activities worldwide are concentrating on a better understanding of the observed GPS ionospheric delay dynamics and the relation to local ionosphere conditions.

Here we present the results of a study addressing daily GPS ionospheric delay dynamics observed at a Croatian coastal area of the northern Adriatic (position ϕ=45°N, λ=15°E) in the periods of quiet space weather in 2007. Daily sets of actual GPS ionospheric delay values were assumed to be the time series of composite signals, consisting of DC, cosine and residual components, respectively. Separate models have been developed that describe components of actual GPS ionospheric delay in the northern Adriatic for summer and winter, respectively. A special emphasis was given to the statistical description of the residual component of the daily distribution of GPS ionospheric delay, obtained by removing DC (bias) and cosine components from the composite GPS ionospheric delay.

Future work will be focused on further evaluation and validation of a quiet space weather GPS ionospheric delay model for the northern Adriatic, transition to a non-Klobuchar model, and on research in local GPS ionospheric delay dynamics during disturbed and severe space weather conditions.