Radar transponders and radar target enhancers have been in use in a variety of applications for many years. Perhaps the most widely-known applications of radar transponders are in Identification Friend or Foe (IFF) and its civilian counterpart, secondary surveillance radar for air traffic control, and as racons in marine navigation and, most recently, as Search And Rescue Transponders (SART) in the Global Marine Distress and Safety System (GMDSS).

A dual channel microwave Doppler-Sensor-Module for 24 GHz is presented. This front end is well suited for true ground speed and distance measurements in all kinds of automotive applications. The microwave components such as oscillator, mixer, antenna and their characteristics in the MIC are discussed. The influence of the antenna pattern and the road surface on the Doppler spectrum is treated in a 3D-field theoretical simulation. This simulation takes the antenna nearfield and the distributed scattering of the road into account.

Marine accident frequencies reported in 20 different sources have been studied and compared. Further than this, comparisons were made with an analysis done by the present authors. There seems to be consistency within the sources in the use of the terms total loss, casualty and accident/incident. The rates were observed to decrease by an order of magnitude going from accident/incident to casualty and likewise from casualty to total loss. The overall frequencies were found to be in the range of 0·0009 to 0·07 total losses per 106 ship miles, 0·03 to 1 casualties per 106 ship miles, and 0·5 to 13 accidents/incidents per 106 ship miles. It was found that the frequency depends on visibility, brightness, geographical environment, age of vessel and size of vessel. Collision and grounding frequencies were found to increase with decreasing visibility, brightness and more restricted waters. Collision frequencies were found to increase with increasing size of vessel. Fire/explosion and structural damage frequencies were found to increase with increasing age, and collisions to decrease with increasing age. No firm trend was found from the effect of flag state or type of vessel.

During the last 5 years there has been a rapid growth in the market for electronic charts. All of the systems that currently use these charts, regardless of their size and complexity, have one thing in common: they are all officially classified as Electronic Chart Systems (ECS). By definition, these systems are not considered to be equivalent to conventional paper charts for the purposes of satisfying SOLAS regulations. For all vessels bound by these regulations, ECS cannot be used in place of paper charts. Consequently, it has been left to commercial companies to provide data for use in these systems. Such data have been of variable quality, and no commercial company currently provides a correction service that matches that provided by most hydrographic offices for paper charts.

This paper examines a Synthetic Aperture Radar (SAR) image of the Thames Estuary aided by the relevant nautical chart, tidal, weather and shipping information of the area. By correlating this information it is possible to identify gross sediment transport which would otherwise be hard and financially expensive to detect. Seabed topography, seabed pipelines, some shipping, coastal zone features and different water parcels can be identified.

It is well known that many collisions occur because one ship turns right whilst the other turns left when in close proximity to one another. Little is known as to why this occurs and, although some simulation models have been established using entropy theory, the problem remains unsolved.

In this paper, an assessment model for uncertainty is reviewed briefly. The concepts of uncertainty and uncoordination of mariners' behaviour in collision avoidance are discussed. A simulation model in conjunction with a DCPA (distance to the closest point of approach) decision-making model using fuzzy programming is introduced to discuss coordination.

This paper discusses the development of Electronic Chart Display and Information Systems (ECDIS) and Electronic Chart Systems (ECS) generally. The role of ECDIS and its implementation is also discussed and compared with the trend by manufacturers to the alternative ECS. International developments in relation to ECDIS and ECS initiatives are looked at briefly and a view on the relationship between government and commercial organizations is presented with reference to the safety of navigation.

Flight trials using an inexpensive Garmin GPS receiver, Century 1 autopilot and a Cessna F172H aircraft to acquire block aerial photography are described. The performance of the whole system in the maintenance of constant sidelap and forward lap in block aerial vertical photography was good. However, the system was not good enough to manoeuvre the aircraft accurately on curved flight paths.

The risk of a close quarters situation arising when a vessel crosses a busy traffic lane, such as one of the separation lanes in operation in the vicinity of the Dover Strait, is usually assessed in terms of the number of encounters or domain infringements likely to occur if no avoidance action were taken. Such calculations, which are based on the theoretical encounter rate, do not normally take into account any enhancement of the risk which may be associated with the simultaneous interaction of a crossing vessel with more than one other ship.

This article treats integration of navigation data from a variety of sensors in a submarine using extended Kalman filtering in order to improve the accuracy of position, velocity and heading estimates. The problem has been restricted to planar motion. The measurement system consists of an inertial navigation system, a gyro compass, a passive log, an active log and a satellite navigation system. These subsystems are briefly described and models for the measurement errors are given.

Four different extended Kalman filters have been tested by computer simulations. The simulations distinctly show that the passive subsystems alone are insufficient to improve the estimate of the position obtained from the inertial navigation system. A log measuring the velocity relative to the ground or a position determining system are needed. The improvement depends on the accuracy of the measuring instruments, the extent of time the instrument can be used and which filter is being used. The most complex filter, which contains fourteen states, eight to describe the motion of the submarine and six to describe the measurement system, including a model of the inertial navigation system, works very well.

This paper, and the following paper, were presented at the 8th Congress of the International Association of Institutes of Navigation held in Beijing, 6–11 September 1994.

This paper starts with a brief overview of cross-rate interference (CRI) and methods developed in the past for estimating the CRI between two Group Repetition Intervals (GRIS). It presents an algorithm for fast calculation of the loss of pulses due to blanking in dual-rate stations. These stations broadcast on the GRIS of two chains but, if pulses of both chains overlap, one GRI is not transmitted at that instant. Furthermore, it will discuss the impact of this blanking on the use of Loran-C signals for transmitting data. A strategy is given for selecting GRIS, based on the presented theory. The paper is based on papers presented at the 1993 WGA technical symposium and the 1993 INA conference.

The earliest record of a requirement for ships to carry lights that the author has been able to find is in the Rhodian Laws. These appear to date from about the 3rd or 2nd century B.C., and were certainly incorporated into Roman Law by A.D. 161, although Ashburner suggests that the earliest known copy dates from Byzantine times, A.D. 600–800. The Laws contain a section intended to prevent collisions between vessels under way and vessels at anchor or stopped.

For farming in the future, positional information is of particular importance. Out of a multitude of positioning systems, GPS/DGPS is the most suitable one. This system does not require any additional infrastructure and at the same time guarantees complete coverage of all tilled surfaces. The major application of positioning with GPS/DGPS is to be seen in the area of local information and documentation. By generating both planning and process data, it facilitates the operation and control of work processes (organic and mineral fertilization, plant protection). In the end, positioning leads to navigation, which, in the case of single vehicles and vehicle pools, will in turn provide completely new possibilities for development and application. For the first time, vehicles without drivers are conceivable. Thus, the completion of any kind of work on schedule, without time limitations, would become possible with the least possible stress for soil and environment.