In May 1993, in support of Eurocontrol's WGS 84 Implementation Programme, a project was undertaken to assess the accuracy of navigation aid coordinates. The exercise involved flying a route over a number of European countries, in an aircraft which was equipped for multi-DME ‘data puddle’ position updating, and which also carried Global Positioning System (GPS) receivers. This test flight, carried out under contract to Eurocontrol, involved two parties, namely the Defence Research Agency (DRA) Bedford, who provided the airborne trials facility and DME data, and the Institute of Engineering Surveying and Space Geodesy (IESSG) at the University of Nottingham, who provided an analysis of the DME coordinate accuracy.

The aim of this test flight was to assess whether it is possible to determine independently the (WGS 84) coordinates of DME ground stations from the air, by using the same DME range measurements which are used to update aircraft position information in-flight. The procedure used to determine DME coordinates involves reversing the position updating principle. Instead of taking the DME ground station coordinates as known points and using the DME range measurements to determine the aircraft's position, the aircraft's position is independently determined (from DGPS) and the range measurements are used to estimate the coordinates of the DME ground stations.

The International Maritime Consultative Organization (now IMO) carriage requirement for ARPA began to take effect in 1984 and became progressively mandatory worldwide; prior to this, for certain classes of vessels trading to the USA, a national requirement was introduced in 1982. These radar plotting aids perhaps constituted the first widespread use of computing power aboard merchant vessels. In implementation, even the early ARPAS were much more than the mere plotting aid which their name suggests. Sophisticated processing gave the navigator a system which offered significant assistance in scenario analysis, with the well known ability to display graphically the effect of a trial manoeuvre being the most active element of the system.

Radar and ARPA are used both for anti-collision purposes and for navigational purposes. The requirements for ‘ground-stabilization for navigation’ and ‘sea-stabilization for collision-avoidance’ seem to exclude each other. Since the development of True Motion radar (TM), there is the need for an input of Own Ship's velocity. Since then, the mode of velocity input and, consequently, the mode of stabilization have been the subject of controversy. The problem became even more important by the introduction of ARPA, by the use of video map overlays and by the introduction of complex integrated navigation systems including radar.

The risks involved in maritime transport are very much greater now than was formerly the case. This has been accompanied by a considerable increase in the damage resulting from certain accidents. Maritime traffic management has been made necessary not only for reasons of safety but also productivity and comprises two main types of measure: first, laying down and enforcing suitable regulations and secondly, providing navigators with real time information which is not available to them on board from the Vessel Traffic Services (VTS).

Section 2 of this paper is a general description of the techniques used in maritime traffic management and an account of possibilities for the future. Section 3 describes a feasibility study for a traffic monitoring aid system based on VTS and using a knowledge based system.

This paper is based on one which was first published in the journal, Recherche Transports Sécurité, issue no. 9, 1993.

A device has been developed to enhance the radar conspicuity of navigation buoys. It is also very effective on small craft. This paper describes the specification and testing of the device and discusses the regulatory position regarding its use.

Map reading has always been and will continue to be a vital military skill. The ability to relate map to ground and vice versa is an essential skill for all ranks. Having determined his position and that of his objective, a soldier must be able to navigate between the two in the most expeditious manner. The advent of the Global Positioning System GPS has not diminished this requirement. Map reading and navigational skills are practical subjects that must be regularly practised and assessed if skills are to remain high.

This paper and the following two papers were presented at the Euronav 94 Conference organized by the DGON and the R1N and held in Dresden in June 1994.

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.

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.

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 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.