The NAVSTAR Global Positioning System: Operation, Accuracy and Error Analysis

[摘要] The NAVSTAR Global Positioning System (GPS) is a United States Department of Defense satellite survey system which is being developed to replace the present TRANSIT system in the 1990s. When fully operational, the system will enable virtually instantaneous and continuous position to be determined throughout the world, 24 hours a day. This dissertation aims to examine the operation of GPS, with particular interest in firstly the various sources of error within the system, and secondly methods of reducing or negating such errors. This leads to an examination of expected final accuracies for GPS. The first three chapters discuss Global Positioning System design and operation in terms of three segments. The Space Segment covers the satellite orbit configuration and the structure of the electromagnetic signals which they transmit. The Control Segment describes how the GPS satellite orbits are obtained, and how predicted orbits are provided for each satellite. The User Segment is both wide and complex, comprising all those methods employed by receivers to obtain a position fix, using the signals transmitted by the GPS satellites. This chapter describes the four main GPS measurement modes (pseudo - r ange, carrier phase, interferometric delay and integrated Doppler), before introducing the other relevant variables in GPS receivers. Some of the more common GPS receivers are also examined in more detail at this point. Following a discussion of height determination with respect to GPS, the main sources of error in the system are studied. Observation, ephemeris, clock, refraction, multipath and instrumental errors are all examined, along with the effect that satellite geometry has on the final accuracy. Methods of improving the accuracy of GPS (for example, various forms of differencing, ionospheric and tropospheric refraction correction, cycle slip detection, antenna design) are then detailed, along with several other possible techniques. The final chapter examines the variation in GPS accuracies, before comparing The system's performance with other survey systems. The peculiarities of GPS survey procedures are also dealt with, and the factors involved in drafting specifications for a GPS survey. A final section discusses GPS applications, and possible future developments within the system. Appendix A tabulates the major characteristics of 25 GPS receivers. This dissertation was completed largely by library research, the information being collected from well over 100 articles, papers and brochures which discuss the Global Positioning System.

[发布机构] University:University of Glasgow

[关键词] Remote sensing, Geographic information science and geodesy, Aerospace engineering