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This thesis describes an Intelligent Differential GPS Navigation System developed for a PhD research project. The first part of the work was to apply differential technology to Global Positioning System to locate the current position of the user with an improved positioning accuracy. The essential part of this Differential GPS system is a Differential GPS Reference Station. This DGPS Reference Station includes a DGPS mathematical model and the corresponding algorithms, which calculates the differential correction messages. These messages are then transmitted to a mobile GPS receiver by a radio data link. By using these corrections, the mobile GPS receiver's positioning accuracy can be improved from about 100 m to 4 m. This DGPS Reference station has been used to implement system software for this research. Differential correction algorithms were modified, characteristics of system components were changed, and different digital filters were also applied at different locations to investigate the impact on system performance. Besides all these capabilities which are needed for the research purpose, this DGPS Reference Station has all the standard functions, and can be used as a standard DGPS Reference Station. The second part of the work was to combine this Differential GPS system with a suitable digital map to form a navigation system. A suitable digital map database was chosen and modified, and the content of the map was then reproduced on the mobile GPS receiver's host PC screen. This digital map, combined with the current location of the user, provides the basic navigational information for the user to reach a desired destination. To help the user further and demonstrate the potential use of the system, an intelligent route-planing algorithm that can produce the optimum route automatically was also designed. The system integration was achieved by the design of the mobile navigation unit and the combination of this mobile navigation unit with the constructed DGPS Reference Station. The final system consists of a DGPS Reference Station, a UHF radio data transmitter, a mobile GPS receiver, a digital map system, a route searching and planing algorithm and a UHF radio data receiver. Field trials were carried out to test the system static and dynamic performances. Repeated experiments showed that both the static and dynamic positioning accuracies were within the range of 4 meters. The constructed system is a prototype navigation system which incorporates the basic navigational functions. It is envisaged that this system can be directly used, or further developed to suit a special need, as required. A typical application of the system would be to guide a user to a desired destination. Other examples include: aircraft autolanding control system, car self-driving, taxi fleet control, criminal tracing and personal navigation systems.

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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The coverage characteristics of the GLONASS constellation is analyzed. The almanac data of GLONASS navigation message are used in the computation according to the operation of the satellites. The ground traces of the GLONASS satellites are plotted. And the probability of visible satellite number is calculated under different latitude conditions. The results are analyzed to give descriptions of the GLONASS constellation. And they are compared with those of GPS's. The conclusion is verified that GLONASS constellation provides better coverage at high latitude.

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Η μέθοδος RAIM αναπτύχθηκε στις αρχές του 1990 καθώς είχε δημιουργηθεί η ανάγκη για τον έλεγχο της λειτουργίας των δορυφορικών συστημάτων πλοήγησης που τότε άρχισαν να δίνονται για χρήση στο ευρύ κοινό μια και το GPS που είναι το πιο ολοκληρωμένο σύστημα δορυφορικής πλοήγησης ήταν αποκλειστικά για στρατιωτική χρήση έως τότε. Η πλοήγηση των αεροσκαφών βασιζόταν έως τότε αποκλειστικά στα ραδιοβοηθήματα κάτι που συμβαίνει μέχρι σήμερα καθώς τα δορυφορικά συστήματα πλοήγησης έχουν συμβουλευτικό μόνο χαρακτήρα και δεν είναι επιχειρησιακά για την πολιτική αεροπορία. Η εξέλιξη της τεχνολογίας και οι ολοένα αυξανόμενες ανάγκες για βελτίωση των συνθηκών πτήσης, δηλαδή να πραγματοποιούνται σε λιγότερο χρόνο οι πτήσεις, με μικρότερο κόστος στα καύσιμα και με μεγαλύτερη ασφάλεια οδήγησε στην εξέλιξη των δορυφορικών συστημάτων πλοήγησης που αποσκοπούν να γίνουν τα βασικά συστήματα πλοήγησης των αεροσκαφών. Στην παρούσα εργασία στην αρχή γίνεται μια αναφορά στα ραδιοβοηθήματα που χρησιμοποιούνται για την πλοήγηση των αεροσκαφών. Έπειτα αναλύονται τα διάφορα συστήματα δορυφορικής πλοήγησης που υπάρχουν και στη συνέχεια αναλύεται τι είναι το RAIM και οι διάφορες μέθοδοι RAIM που υπάρχουν. Μετά παρουσιάζεται το LPV-200 που δείχνει την ανάγκη για βελτίωση του RAIM για να υπάρχει και κάθετη πλοήγηση και ύστερα ακολουθεί η ανάλυση του ARAIM, του RRAIM και του MHSS RAIM που είναι η εξέλιξη του συμβατικού RAIM για να καλύψει τις καινούριες απαιτήσεις του ICAO για κάθετη πλοήγηση. Στο τέλος γίνονται μετρήσεις σε GPS δορυφόρους σε πραγματικό χρόνο για να αναλύσουμε την λειτουργία του RAIM. / The RAIM method was developed at early of 1990s as it had created the need of controlling the operation of satellite navigation systems which then began to be given for use in the general public since the GPS which is the more integrated satellite navigation system was reserved for military use until then. Navigation of aircrafts until then was based exclusively only on navigational aids something that is happening until today since the satellite navigation systems are consultative and not operational in civil aviation. The evolution of the technology and the increasing needs for improvement of flight conditions, such as less time for the flight, with less cost on fuel and greater safety led to the development of satellite navigation systems which aims to be the basic navigation system of the aircraft. In this project at the begging there is a reference to the navigational aids used for aircraft navigation. After we refer to the different satellite navigation systems that exists and then we analyze what is RAIM and what are the various RAIM methods. Later we present the LPV-200 which indicating the need for improving the RAIM in order to have vertical guidance and then we analyze the ARAIM, RRAIM and MHSS RAIM which is the development of the conventional RAIM to meet the new requirements of ICAO for vertical guidance. At the end we take measurements of GPS satellites in real time in order to analyze the RAIM performance.