Integration of GPS/INS navigation systems is a common topic for aeronautical and road applications. The use of these technologies for personal localisation requires more than just portable sensors and a change of ergonomics; it requires a totally different approach for dead reckoning algorithms. This paper will focus on different human applications and reveals the particular problem encountered.

In the conventional integrated navigation system, the statistical information of the process and measurement noises is considered constant. However, due to the changing dynamic environment and imperfect knowledge of the filter statistical information, the process and measurement covariance matrices are unknown and time-varying. In this paper, a multirate adaptive Kalman filter is proposed to improve the performance of the Error State Kalman Filter (ESKF) for a marine navigation system. The designed navigation system is composed of a strapdown inertial navigation system along with Doppler velocity log and inclinometer with different sampling rates. In the proposed filter, the conventional adaptive Kalman filter is modified by adaptively tuning the measurement covariance matrix of the auxiliary sensors that have varying sampling grates based on the innovation sequence. The performance of the proposed filter is evaluated using real measurements. Experimental results show that the average root mean square error of the position estimated by the proposed filter can be decreased by approximately 60% when compared to that of the ESKF.

In planning routes between well-defined points of departure and arrival, both aircraft and ships can take into account forecast values of certain geophysical parameters so that the route chosen is in some sense optimized. For aircraft flying the North Atlantic, the methods used are described in the papers by Attwooll, Bennett, and Monk (all 1982). There have been a number of papers on ship-routeing; they were reviewed by Motte and Calvert (1988). It should be noted that whereas for aircraft the dominant consideration is the wind (for which the maritime equivalent is the current), ship-routeing on the trans-oceanic scale is dominated by considerations of waves. However, on smaller scales, currents can be the dominant consideration: for example, see the paper by Fales (1991). That paper does not make use of the basic theory that was applied to the aeronautical problem in the 1940s. Although the work reported here is orientated to aeronautical applications, it clearly has ramifications for certain maritime problems.

According to the mid-term review of the EU White Paper on Transport, short sea shipping is expected to grow at a rate of 59% in metric tonnes, from 2000 to 2020. If we consider that the overall expected growth in freight exchanges is of some 50%, sea transport is one of the most feasible ways to reduce traffic congestion on European roads. High speed vessels are a possible way to compete with road transport on certain routes; however, these ships are highly affected by heavy weather. This paper analyses the weather influence on several short sea shipping routes to be served by fast ships.

A swath sounding system is under development which is capable of being towed from ships of opportunity. The principle on which it is based is an acoustic interferometer to which a vernier has been added to resolve the ambiguity of phase ramp identification. The ‘fish’ is equipped with both rotational and translational attitude sensors, though no attempt is made to stabilize it. This is in the interest of size and hence of both instrumental and deployment economy.

The paper, which was presented at Oceanology International 1982 at Brighton, proposes a novel method to permit replication of the swath depth measurements, and also to provide an independent means of ground scale correction, which may obviate the need to deploy a positioning network for deep-water high-resolution swath surveys.

This paper describes one of the key features of the JTIDS/Link 16 tactical data-link, namely its relative navigation facility. A brief overview of the general features of the JTIDS system is given to provide the necessary background to the navigation aspects, and some mention is made of the message-exchange facilities. The main part of the paper describes how the JTIDS system provides the capability to perform accurate navigation, and discusses the basic principles of its operation. Some applications of the navigation function which enhance operational effectiveness are then described. The following topics are covered:

(ii) JTIDS Architecture

(i) Definition of JTIDS/Link 16

(iii) Principles of Relative Navigation

(iv) Source Selection

(v) The Kalman Filter

(vi) Time Synchronization

(vii) The Use of Relative Navigation

(viii) The Relative Grid

The high cost of inertial units is the main obstacle for their inclusion in precision navigation systems to support a variety of application areas. Standard inertial navigation systems (INS) use precise gyro and accelerometer sensors; however, newer inertial devices with compact, lower precision sensors have become available in recent years. This group of instruments, called motion sensors, is six to eight times less costly than a standard INS. Given their weak stand-alone accuracy and poor run-to-run stability, such devices are not usable as sole navigation systems. Even the integration of a motion sensor into a navigation system as a supporting device requires the development of non-traditional approaches and algorithms. The objective of this paper is to assess the feasibility of using a motion sensor, specifically the MotionPak™, integrated with DGPS and DGLONASS information, to provide accurate position and attitude information, and to assess its capability to bridge satellite outages for up to 20 seconds. The motion sensor has three orthogonally mounted ‘solid-state’ micro- machined quartz angular rate sensors, and three high performance linear servo accelerometers mounted in a compact, rugged package. Advanced algorithms are used to integrate the GPS and motion sensor data. These include INS error damping, calculated platform corrections using DGPS (or DGPS/DGLONASS) output, velocity correction, attitude correction and error model estimation for prediction. This multi-loop algorithm structure is very robust, which guarantees a high level of software reliability. Vehicular and aircraft test trials were conducted with the system in land vehicle mode and the results are discussed. Simulated outages in GPS availability were made to assess the bridging accuracy of the system. Results show that a bridging accuracy of up to 3 m after 10 seconds in vehicular mode and a corresponding accuracy of 6 m after 20 seconds in aircraft mode can be obtained, depending on vehicle dynamics and the specific MotionPak™ unit used. The attitude accuracy was on the order of 22 to 25 arcmin for roll and pitch, and about 44 arcmin for heading.

In Network RTK (Real-Time Kinematic) positioning, the multiple corrections from the reference stations, which constitute a network, are interpolated for the user location through appropriate interpolation models. There exist various methods to model spatial decorrelation errors from the tropospheric and ionospheric delay, which are the main contributors of the multiple corrections. Since tropospheric delay is largely affected by height differences, the heights of the multiple reference stations should be considered when selecting the appropriate interpolation methods. This work provides a comparative analysis of the different levels of performance of each height-related multiple correction interpolation method. In addition, this study proposes to add constraints to the conventional height-related interpolation methods that are derived from the characteristics of the tropospheric zenith delay variation over height. The actual Global Positioning System (GPS) observations are collected from selected reference station networks located in the USA for performance evaluation. As a result, the proposed solution yields improved vertical positioning accuracy by approximately 10% compared to the conventional interpolation methods for the selected networks.

To eliminate the impact of the Doppler effects caused by the motion of the Mars explorer, a novel X-ray pulsar navigation method based on a closed-loop filter is proposed. In the pulsar signal observation period, the Doppler velocity predicted by the orbit dynamic model and the prior information is utilised to compensate the X-ray photon time-of-arrival (TOA). However, because of the error in prior information, there is a bias caused by the Doppler compensation in the pulse time-of-arrival. The pulse TOA bias and the Mars explorer's state estimation error are correlated, which results in the decline of the Kalman filter performance. To deal with this problem, we build the TOA measurement model with respect to the state estimation error, and utilise the closed-loop extended Kalman filter (EKF) as the navigation filter, where the predicted state error is adopted as the state estimation. The simulation results demonstrate the feasibility, real-timeliness and effectiveness of the proposed navigation method. The navigation method based on the closed-loop EKF using the measurement model with the Doppler effects is more accurate than the traditional one.

The ship safety domain plays a significant role in collision risk assessment. However, few studies take the practical considerations of implementing this method in the vicinity of bridge-waters into account. Therefore, historical automatic identification system data is utilised to construct and analyse ship domains considering ship–ship and ship–bridge collisions. A method for determining the closest boundary is proposed, and the boundary of the ship domain is fitted by the least squares method. The ship domains near bridge-waters are constructed as ellipse models, the characteristics of which are discussed. Novel fuzzy quaternion ship domain models are established respectively for inland ships and bridge piers, which would assist in the construction of a risk quantification model and the calculation of a grid ship collision index. A case study is carried out on the multi-bridge waterway of the Yangtze River in Wuhan, China. The results show that the size of the ship domain is highly correlated with the ship's speed and length, and analysis of collision risk can reflect the real situation near bridge-waters, which is helpful to demonstrate the application of the ship domain in quantifying the collision risk and to characterise the collision risk distribution near bridge-waters.

Two pre-processes for Automatic Identification System (AIS) trajectories commonly reported in the maritime knowledge discovery literature are trajectory simplification and event identification. Both pre-processes reduce storage and computational expenses by reducing the number of data points to be used in an analysis. This paper presents an event identification and trajectory simplification method based on behaviour identification and translation. Trajectory segments deemed to correspond to coastal or ocean navigation are translated into equivalent passage plan segments; a succinct description of the movements and behaviour of the ship. As a trajectory simplification method, it provides two main advantages over commonly used trajectory simplification methods: more meaningful simplified trajectories with better encoding of basic behaviours and the possibility to retain interesting behaviours in full resolution. As an event identification method, it is capable of differentiating between normal ocean or coastal navigating behaviour and complex or interesting behaviour, such as pilotage, reaction to a traffic conflict, or an involuntary deviation from the passage plan.

Real-time Precise Point Positioning (PPP) relies on the use of accurate satellite orbit and clock corrections. If these corrections contain large errors or faults, either from the system or by meaconing, they will adversely affect positioning. Therefore, such faults have to be detected and excluded. In traditional PPP, measurements that have faulty corrections are typically excluded as they are merged together. In this contribution, a new PPP model that encompasses the orbit and clock corrections as quasi-observations is presented such that they undergo the fault detection and exclusion process separate from the observations. This enables the use of measurements that have faulty corrections along with predicted values of these corrections in place of the excluded ones. Moreover, the proposed approach allows for inclusion of the complete stochastic information of the corrections. To facilitate modelling of the orbit and clock corrections as quasi-observations, International Global Navigation Satellite System Service (IGS) real-time corrections were characterised over a six-month period. The proposed method is validated and its benefits are demonstrated at two sites using three days of data.

A prerequisite for a Global Positioning System (GPS) attitude determination is to calculate baselines between antennae with accuracy at the millimetre level simultaneously. However, in order to have a low cost attitude determination system, a set of Commercial-Off-The-Shelf (COTS) receivers with separate clocks are used. In this case, if the receiver clocks are not precisely synchronized, the baseline vector between antennae will be calculated from the GPS signals received at different times. This can be a significant error source for high-kinematic applications. In this paper, two equivalent and effective approaches are developed to compensate this significant bias for baseline estimation and attitude determination. Test results using real airborne GPS data demonstrate that the receiver time misalignment between the two receivers can result in a 5 cm baseline offset for an aircraft with a 50 m/s velocity; the corresponding attitude errors can reach about 0·50° in yaw and 0·10° in pitch respectively for the attitude determination system with a baseline length of 3·79 m. With the proposed methods, these errors can be effectively eliminated.

An escort tugboat comes to the aid of a vessel when that vessel is navigating in confined waters and at a speed that is usually higher than six knots. In the escort manoeuvre, two systems come into play. One is the propulsion and steering of the vessel. The other involves the tug winch in terms of the tension it exerts and the length of towline released. In this way, the tug winch becomes a key piece of equipment. Along with the difficulties of carrying out the manoeuvre itself are the risks resulting from the operation of the winch. For this reason, automatic manoeuvring systems have been developed to facilitate this operation. They consist of information technology applications that help the skipper with manoeuvring the tug. At the same time, they make it possible to display and monitor the most important parameters of the towing winch. This study will describe a control system for the towline so that it can help carry out the towing manoeuvre with an escort tug. It indicates the control parameters for the manoeuvre, as well as the operational variables of the winch on which the system runs.

The purpose of this paper is to show the effect of incorporating various discrete grid systems in a micro-based, ship weather-routeing system, which employs Bellman's dynamic programming algorithm, and either a cost-objective or time-objective performance measure. A simple ship speed and power function is utilized, in the cost computation. The calculation of the least-cost/least-time route is briefly described, but it is the derivation of the discrete grids and their influence on the route decisions that forms the paper's emphasis. The measure of cost within this paper is necessarily notional.

A curve that cuts all meridians of a rotating surface at the same angle is called a loxodrome. If the shape of the Earth is approximated by a sphere, then the loxodrome is a logarithmic spiral that cuts all meridians at the same angle and asymptotically approaches the Earth's poles but never meets them. Since maritime surface navigation defines the course as the angle between the current meridian and the longitudinal direction of the ship, it may be concluded that the loxodrome is the curve of the constant course, which means that whenever navigating on an unchanging course we are navigating according to a loxodrome.

The International Maritime Organization has mandated carriage requirements for VHF Automatic Identification System (AIS) on vessels over 300 tons by 2007 (IMO SOLAS: 1974 and IMO Resolution MSC.99(73)). The AIS will transmit a vessel's position and voyage data to other AIS-equipped vessels and shore-based authorities. It was envisioned that AIS data could enhance the safety of navigation by allowing vessels to quickly identify each other and use Digital Select Calling (DSC) to arrange maneuvers. We will discuss the history and the development of AIS, the technical issues surrounding its use by the mariner as a navigation tool and the pros and cons of the proposal by the US Coast Guard (USCG) to use AIS as a means of surveillance for Maritime Domain Awareness.

To reduce the operational complexity of the multipath estimating delay lock loop (MEDLL) and improve its anti-multipath performance for strobe correlators, a combination anti-multipath scheme, namely, the MEDLL on-strobe correlation technique, is proposed for global navigation satellite system (GNSS) signal processing. Short-delay multipath rays are separated from the strobe correlation function by the MEDLL mechanism; the dot product between the estimation residue and the standard correlation function or the BOC-PRN correlation function is then computed to eliminate the potential tracking ambiguity. Finally, this non-coherent combination result is sent to the loop filter to obtain anti-multipath code tracking. The proposed method is analysed via simulator data with a software receiver under different front-end bandwidth conditions. The results corroborate the better multipath mitigation capability and lower computational burden, although it is still difficult to eliminate all multipath interference, especially when the front-end bandwidth is insufficient.

Applying the existing domain model in ship domain research in a restricted area can be difficult owing to multiple factors that must be considered. This study presents a new domain model that can be applied in such environments. According to Endsley's theory of situation awareness, people have their own criteria in decision making based on factors such as individual and environmental factors. To investigate these factors, 125 seafarers were interviewed and threshold values based on their awareness were examined. The factors were evaluated as the closest points of approach. Domain modelling was performed based on these seafarer awareness values; then, the existing and awareness domains were compared, revealing that the awareness-based domain of seafarers is more affected by ship manoeuvrability than by ship size and speed, unlike the findings of existing domain research. Therefore, this study presents a new domain model that is both realistic and practical in a confined area, including various factors considered by seafarers based on the awareness values formed.

In this paper, a novel Strong Tracking Sigma-Point Predictive Variable Structure Filter (ST-SP-PVSF) is presented as a further development of the Adaptive Predictive Variable Structure Filter (APVSF) for attitude synchronisation during Satellite Formation Flying (SFF). First, the sequence orthogonal principle is adopted to enhance the robustness of the APVSF for any nonlinear system with uncertain model errors. Then, sigma-point sampling strategies (such as unscented transfer, cubature rule and Stirling's polynomial interpolation) are introduced to extend the APVSF with the ability to capture the second central moment's information on the model errors to update the system model with higher precision. The new methodology has advantages in dealing with the various types of uncertainties or model errors compared with the APVSF. In addition, it does not need to choose the limit boundary layer ψlim it for system estimation, which reduces the sensitivity to the initial parameters and improves its adaptive ability over the APVSF. Simulations are performed to demonstrate that the proposed method is more suitable for attitude synchronisation estimation of the SFF system.