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The Global Positioning System (GPS) has been an undoubted success and a great many applications have benefited from it. It does however have limitations, which make its use in certain environments, and for certain tasks, difficult or indeed impossible.In recent years a second satellite based navigation system, the Global'naya Navigatsionnaya Sputnikov Sistema (GLONASS) has become increasingly available. A great deal of interest has been expressed in combining both these systems, in the hope that combined GPS/GLONASS technology will present significant benefits under conditions where GPS alone has struggled. The research described in this thesis was undertaken to examine the potential benefits and problems of such a combination. This has been primarily achieved through the modification of the existing GPS processing software of the Institute of Engineering Surveying and Space Geodesy (IESSG) to accept GLONASS observations. The analysis of data collected under controlled conditions and processed through this software has highlighted biases in the pseudorange measurements from the GLONASS satellites. This is due to the fact that each GLONASS satellite broadcasts on a different frequency, which is then delayed by slightly different amounts through the Radio Frequency (R/F) section of the receiver. If these R/F sections were identical in each receiver, this error source would cancel, but this has not been found to be the case with the receivers used in this research. Interestingly, no such biases have found to be present in the GLONASS carrier phase observations. Various tests have been performed and the data processed through both IESSG and commercially available software. These have highlighted that there are undoubted potential benefits of using combined GPS/GLONASS receivers in environments where visibility is restricted. Under ideal conditions however, the effect of any benefit is reduced, and indeed the biases present in the GLONASS pseudoranges may slightly degrade the accuracy of differential positioning. The software developed has already been used in other research projects within the IESSG. Although the future of the GLONASS system is somewhat uncertain, any future changes to it should be easily accounted for within the code. There is however a real need to further develop and incorporate cycle slip detection software, especially for GLONASS observations, and to investigate the possibility of solving for the biases in the GLONASS pseudoranges.

In recent years, the market served by satellite positioning systems has expanded exponentially. It is stimulated by the needs of an ever increasing number and variety of scientific, business and leisure applications. The dominant system is the USA's GPS, or Global Positioning System. However, GPS is not a panacea for all positioning tasks, in any environmental situation. For example, two of the fastest growing applications, vehicle tracking and personal location, operate in an often harsh signal reception environment. This can be so severe that even with the current 29 working satellites, GPS may struggle to perform. In exceptional circumstances it can fail to provide a positioning service at all. The simplest way to improve the situation when signal reception is poor, is to add similar signals from alternative satellite systems. This has already been achieved by combining GPS with the Russian satellite positioning system, Global'naya Navigatsionnaya Sputnikova Sistema, abbreviated to GLONASS. The combination of GPS with GLONASS is referred to here as Hybrid. But how good is Hybrid relative to GPS, and how can performance be evaluated objectively? The research project presented here set out to answer this question, and to understand the situations in which Hybrid failed, and ask what solutions were then available to fulfil a positioning task. The problems associated with integrating one satellite positioning system with another, their potential inconsistencies and their impact on positioning errors were also examined. This field of research is relevant to Hybrid as defined here, and also to other mixed systems, for example GPS with EGNOS, a European geostationary satellite system, and GPS with Galileo, a proposed global system controlled by the Europeans. The issues were addressed from the viewpoint of practical usage of the positioning systems. Hence the many and varied experiments to quantify positioning performance using both static receivers, and a variety of platforms with wide ranging levels of vehicle dynamics. The capability of satellite positioning systems to work in the harshest environments, was tested in the proposed Olympic sport of bob skeleton. This involved the development of the acquisition system, and a number of programs. The latter were equally applicable to the ensuing work with road vehicles, and the quantitative assessment of positioning performance relative to a truth. The processes established to manipulate, import, and merge satellite based vehicle tracking data with Ordnance Survey digital mapping products, have already been used in four other projects within the School of Civil Engineering. The software to regularise positioning interval, smoothing processes, and to compare tracking data with a truth, have been similarly provided. Without major funding the outlook for GLONASS and hence Hybrid looks bleak, and it is predicted that without replenishment the constellation may fall to six satellites by the end of 2001. However as mentioned above, the issues identified, and ideas and software developed in this research, will be directly applicable to any future hybridisation of GPS with Galileo.

GPS and Inertial Navigation Systems (INS) are increasingly used for positioning and attitude determination in a wide range of applications. Until recently, the very high cost of the INS components limited their use to high accuracy navigation and geo-referencing applications. Over the last few years, a number of low cost inertial sensors have come on the market. Although they exhibit large errors, GPS measurements can be used to correct the INS and sensor errors to provide high accuracy real-time navigation. The integration of GPS and INS is usually achieved using a Kalman filter which is a sophisticated mathematical algorithm used to optimise the balance between the measurements from each sensor. The measurement and process noise matrices used in the Kalman filter represent the stochastic properties of each system. Traditionally they are defined a priori and remain constant throughout a processing run. In reality, they depend on factors such as vehicle dynamics and environmental conditions. In this research, three different algorithms are investigated which are able to adapt the stochastic information on-line. These are termed adaptive Kalman filtering algorithms due to their ability to automatically adapt the filter in real time to correspond to the temporal variation of the errors involved. The algorithms used in this research have been tested with the IESSG's GPS and inertial data simulation software. Field trials using a Crossbow AHRS-DMU-HDX sensor have also been completed in a marine environment and in land based vehicle trials. The use of adaptive Kalman filtering shows a clear improvement in the on-line estimation of the stochastic properties of the inertial system. It significantly enhances the speed of the dynamic alignment and offers an improvement in navigation accuracy. The use of the low cost IMU in a marine environment demonstrates that a low cost sensor can potentially meet the requirements of navigation and multi-beam sonar geo-referencing applications.

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This work is concerned with an examination of how the Merchant Navy Navigators use the information provided by the different aids. It is divided into three main parts. First are a series of experiments where seafarers studying for their Master’s certificate were presented with cards containing information from a number of different navigational aids, and asked to plot the position lines on a chart and then decide where they would consider the ships' position to be. The second part was the design and construction of a simple non-interactive simulator based on slide displays and video recordings. The aids used were visual bearings, radar, Decca and the echo sounder. The information was taken from instrument readings recorded on board the training ship "Sir John Cass" during a voyage along the East coast from Southwold to Harwich. A number of flashing lights were included in the design to simulate the keeping of a lookout. In the third part a similar group of subjects were asked to navigate a ship on two simulated voyages of half an hour's duration each, while at the same time to log the number of lights they observed. As a measure of their navigational ability they were asked to prepare a course to steer and an E.T.A. for a point about half an hour's steaming ahead of the position at the end of each exercise. A total of 17 dependent variables were identified during the experiment and these were tested in pairs for correlation. From the results of these experiments it was possible to produce an order of the subjects' preference for the different aids, to demonstrate that the subjects preferred to use only two position lines when fixing their position and to examine how the subjects used these aids.

Considerable interest has recently been shown in the field of marine traffic engineering. Real life data sources made available for maritime studies are often expensive and inconvenient to collect. The marine radar simulator presents the researcher with a relatively inexpensive and readily available source of navlgatlonal data. With the improvement of remote vessel traffic monitoring systems the potential for inexpensive real life data analysis Is enhanced. The work of this study has been to allow the analysis of data archived from the Channel Navigation Information Service Automatic Data Processing system (CNIS AOP) installed at St. Margarets Bay Dover using contemporary digital computer graphical facilities, and to compare mariners' behaviour In a real life and simulator collision avoidance situation. For this comparison certain navigational situations known as encounters have been automatically detected using an extension of the Range to Domain Over Range Rate (RDRR) method (Colley et al 1983), referred to as the RDRR+ technique. A statistical comparison has been completed using non parametric techniques.

Air traffic congestion problems in many areas of the world are well known and have been highly publicised in recent years. This airspace dilemma, which results in delays and other undesirable knock-on effects, is escalating at a phenomenal rate and requires immediate attention. Correspondingly, there is concern about safety standards in some worldwide airspace regions. In addition, it is imperative that the significant projected growth in air transport movements over the next two decades is accommodated. Thus, there is an urgent need to solve the current airspace problems and plan in a responsible manner to meet forecast demand. Solutions to these predicaments have been developed and are encompassed under the auspices of the term 'future air navigation systems'. The systems include technologies and procedures that merge to optimise the potential of airport and airspace resources so that the capacity, flexibility and safety of these resources are maximised, while delays and their operating costs are minimised. Future air navigation systems use automated communications. navigation and surveillance technologies to provide enhanced air traffic management through continuous information on aircraft positions and intention, so that reductions in separation are possible without compromising safety. However, confusion exists regarding what technologies and procedures constitute these future air navigation systems. Additionally, their current worldwide integration status is not as advanced as it should be and, in fact, remains largely unknown. Indeed, their successful introduction is far from guaranteed at present. Therefore, this research addresses these requirements by evaluating and improving implementation of tile systems on a global basis. Ultimately, this thesis provides a comprehensive analysis that discovers what systems are pertinent and whether or where they have been applied to date, in addition to developing and validating a framework strategy for improved introduction of the future air navigation systems around the world.

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