Motion compensation is a significant part of an airborne remote sensing system. A Position and Orientation System (POS) can directly measure the motion information of an airborne remote sensing payload that can improve the quality of airborne remote sensing images. Gravity disturbance, information on which is often ignored due to being difficult to acquire in real-time, has become the main error source of POS in the development of inertial components. In this paper, a new real-time gravity compensation method is proposed, which includes the gravity disturbance as the error states of a POS Kalman filter, and an accurate gravity disturbance model is constructed using a time-varying Gaussian-Markov model based on a high-precision gravity map, whose resolution is enhanced by a new interpolation method based on Gaussian Process Regression (GPR). A flight experiment was conducted to evaluate the efficiency of the proposed method and the results showed that the proposed method performs well when compared with other real-time gravity compensation methods.

A novel autonomous positioning approach based on X-ray pulsars is proposed in this paper. First, the principles of the pulsar–based measurement model and the inter-satellite range model in the autonomous positioning of satellite constellations are presented. The observability of the pulsar-based measurement model is then shown. Second, the autonomous positioning algorithms, including measurement models and orbital dynamics models, are formulated using an unscented Kalman filter to estimate the position vectors of satellites. Finally, the feasibility of the proposed measurement scheme compared with an inter-satellite range scheme is illustrated by numerical simulation. The results show that the proposed approach can keep the satellite state convergent, and achieve position accuracies of 2 m. The proposed scheme provides a promising approach for autonomous absolute positioning of constellation systems by using X-ray pulsars.

In this work, a new concentric circles detection method for object detection is proposed. It has been applied to the images of a commercial radar, captured with a Charge-Coupled Device (CCD) camera. The processing includes the detection of centres and concentric circles in the images and the identification of the radar scale. Several methods found in the literature have been applied and compared with our novel proposal for multiple concentric circles detection, called “Propagation Method based on Circular Regression”. This methodology has been validated with real radar images, proving its efficiency in obtaining the distance of any object to a marine vessel, with high accuracy and low computational cost, in real time. This system can not only be applied to most existing radars in the market by adjusting the parameters of each model but our proposal for concentric circle detection can be also applied to other sensing applications.

Ultra-rapid products have the advantage of being used in real-time positioning with no external connections. In this study, these products provided by the international GNSS Monitoring and Assessment System (iGMAS) for four global constellations (GPS, GLONASS, Galileo and BDS-3) were assessed in terms of service rate and accuracy in navigation. In this regard, a MATLAB-based in-house code solving the problem was developed for all possible combinations of the constellations. To explore the effectiveness of the iGMAS products, the same dataset has been also processed using GFZ rapid products. The results demonstrate that the GPS and Galileo solutions were substantially comparable to the rapid products concerning service rate and accuracy, but that the GLONASS and BDS-3 iGMAS products require some enhancements. In addition, the Galileo solution produced remarkably good results both individually and in combination. The GPS/GLONASS/Galileo/BDS-3 SPP solution generated a mean root mean square (RMS) error of 0 ⋅ 54 m horizontally and 0 ⋅ 89 m vertically. Thus, GPS-only, GLONASS-only, Galileo-only and BDS-3-only solutions were improved by 42%, 79%, 28% and 74% in 3D mean RMS error with the quad system solutions, respectively.

Knowledge of surface currents is of fundamental importance in many diverse marine activities; for example in navigation, offshore engineering and operations, and in the prediction and monitoring of the movement of pollutants. In those areas of scientific research directed towards improved understanding of climate, and towards the modelling and prediction of currents, studies of exchanges of heat and momentum between atmosphere and ocean also require detailed knowledge of mean and fluctuating components of near-surface flow.

Both the argument and the geometry in this paper require careful study before they can be appreciated; it is hoped that the following notes, which are restricted to purely geometrical considerations, will assist readers to understand them.

The author's fundamental argument is that it is geometrically impossible for ships A and B, at distance r apart and moving with constant speeds v and u, to approach each other more closely than distance d (less than r) if the courses of ships A and B are each restricted to a semi-circular anti-collision sector, depending only on the angle δ sin δ = d/r, and on an agreed universal convention. This is illustrated in Fig. 1 in which the two sectors are indicated by vv' for ship A and uu' for ship B. Adopting the convention that the ships pass ‘port to port’, the permissive anti-collision sector for each ship is, relative to the bearing of the other ship, from δ to starboard, increasing to 180° and to port from 180° to 180° −δ . This is equivalent to restricting the course so that the other ship bears more than δ to port or more than 180°−δ to starboard.

What are we doing it for? Datatrak designed, built and prepared for the transport market, a complete Automatic Vehicle Location and Reporting System (AVLRS) that covers 95 percent of the road system of Great Britain.

A system which yields the automatic positioning of a ship from computer analysis of marine radar images of nearby coastlines has been tested on data from the survey vessel Maxwell while proceeding in and out of Halifax harbour. Differences between radar-determined position fixes and those obtained by a microwave navigation system with an error of the order i o m show little evidence of additional error when the origin of the radar images used as ‘reference map’ is within 500 m of the actual position. As the distance increases the accuracy slowly decreases.

Before the middle of the 19th Century, sailing vessels under way at night did not set a light. This paper investigates the reasons for this practice and explains the development of navigation lights which culminated in the requirement for both steamships and sailing vessels to display lights at night.

The estimation of collision danger is often required by harbour authorities and others for planning fairways or for increasing the safety of navigation. Fujii1 gives an approximate formula for the probability of collision in a waterway where the density of traffic, the size distribution of ships and the average speed are known. Fujii's formula is however only applicable where the traffic has been surveyed and traffic patterns are well known. Some simple method is required for estimating collision danger, especially for harbours where traffic patterns are complicated and the information available on marine traffic engineering is comparatively small.

Most of the radar systems used in operating marine vessel traffic management services experience problems, such as track loss and track swap, which may cause confusion to the traffic regulators and lead to potential hazards in the harbour operation. The reason is mainly due to the limited adaptive capabilities of the algorithms used in the detection process. The decision on whether a target is present is usually based on the amplitude information of the returning echoes. Such method has a low efficiency in discriminating between the target and clutter, especially when the signal-to-noise ratio is low. With modern signal processing techniques more information can be extracted from the radar return signals and the tracking parameters of the previous scan. The objectives of this paper are to review the methods which are currently adopted in radar target identification, identify techniques for extracting additional information and consider means of data analysis for deciding the presence of a target. Instead of employing traditional two-state logic, it is suggested that the radar signal should be allocated in terms of threshold levels into fuzzy sets with its membership functions being related to the information extracted and the environment. Additional signal processing techniques are also suggested to explore pattern recognition aspects and discriminate features which are associated with a return signal from those of clutter.

For high-precision real-time kinematics (RTK) and safety-of-life Global Navigation Satellite Systems (GNSS), it is critical to track the carrier reliably without interruptions. We develop hardware-oriented robust on-line cycle slip and loss detection logic for a single-frequency stand-alone aviation receiver. The moving average statistics of time-differenced frequency-lock loop (FLL) are shown to provide a robust and fixed detection threshold for cycle loss detection. A Monte-Carlo simulation shows that the detection performance remains robust when aviation dynamics from minimum operational performance standard (MOPS) are added to a simulated strong scintillation.

This paper discusses the main issues of today's maritime navigation and its safety and security systems. Fast development of sciences and technologies, further fast development in the shipping industry, but mainly the appearance of the new very dangerous threats at sea that appeared at the beginning of this century, deeply influence the safety and security of maritime navigation and its systems. These factors are the main reasons for writing this paper.

Graduating error distributions by families of curves has a long and distinguished history. In seeking a class of frequency distributions which graduate navigational data, Anderson and Ellis are motivated by the well-known shortcomings of the normal distribution which so often fails to do justice to the data in the tails of the distribution. They generalize the one parameter (σ) zero-mean gaussian family to a two parameter (α, β) family which is in fact the Pearson Type VII class. They then observe that this class graduates published navigational distributions very wells.

The probability of a human-caused incident occurring during dynamic positioning (DP) drilling operations is determined in this paper using binary logistic regression models built with data on 42 incidents that took place during the period 2011–2015. For each case, a range of variables characterising the configuration of the DP system, weather conditions and water depth are taken into account. These variables are taken into account to develop a logistic regression model that shows the likelihood of an incident being caused by human error. The results obtained show that human-based incidents are significantly more likely to occur when there is a lower usage of thrusters. These results are useful for focusing our attention on variables that may be associated with incidents attributable to human error, as well as for setting operational limits that could help to prevent these incidents and improve safety during these operations.

Cellnet/British Telecom (BT) has been active in the area of GPS/GSM location and application research for over five years. Cellnet/BT have undertaken considerable development and field trials of various GSM methods for location positioning, which have resulted in several patent registrations. Recent R&D projects undertaken by the Mobility engineering team at BT Labs. include MOSA (Mobile Social Alarm) and City Guide using GPS positioning data to deliver value-added applications and services for both the general public and business users. A critical factor to the successful development of innovative value-added services is co-operation with partners, to promote and evolve open standards for GSM location.

The autonomous navigation of navigation and positioning systems such as the Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS) was motivated to improve accuracy and survivability of the navigation function for 180 days without ground contact. These improvements are accomplished by establishing inter-satellite links in the constellation for pseudo-range observations and communications between satellites. But observability issues arise for both ephemeris and clock since the pseudo-range describes only the relative distance between satellites. A differential measurement method is proposed to measure the rotation of the constellation as a whole for the first time. The feasibility of the proposed method is verified by simulations.

Although GPS positioning errors are now well described, there are still some uncertainties regarding the impact of some rare space weather phenomena on GPS positioning accuracy. Solar eclipses have been considered as one source of such rare events, so the 1999 solar eclipse gave the opportunity to collect horizontal GPS positioning data for further analysis. The results of statistical analysis show no deterioration of horizontal GPS positioning accuracy. Space weather, ionospheric and geomagnetic conditions were also carefully analysed and showed no significant activity. In conclusion, the experiment confirmed negligible impact of the 1999 solar eclipse on horizontal GPS positioning accuracy, and opens discussion concerning application of satellite positioning systems in space and ionospheric weather monitoring.

In our present age, radio communication and navigational aids are taken without comment throughout the aviation industry. However, all developments must start somewhere and it is the intention of this paper to look into the earliest days of “wireless” and its gradual application to aviation.

The first step was, as far as I can ascertain, in October 1866 when Mahlon Loomis flew a kite from a mountain top in Virginia, USA. He had fitted a copper mesh to the kite and connected this to a copper wire. Between the wire and earth he connected a galvanometer which, he noted, deflected from static electricity. On flying an identical kite at a similar height some fourteen miles away, if the copper wire were earthed, the deflection on the galvanometer changed. However, if the kite wires were of different length, this effect was not observed. For this, in 1872, he was issued with a US Patent 129971 for “wireless telegraphy” but, as far as we know, apart from a few fading freehand notes, (See Figure 1) no details of his apparatus survive, so it must remain a matter of conjecture what was actually achieved.