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Fundamentals of Global Positioning System Receivers A Software Approach - Chapter 9

GPS Software Receivers Chương này có thể được coi là một bản tóm tắt của tất cả các chương trước. Như đã đề cập trong chương 1, cuốn sách này không đi theo con đường tín hiệu của một máy thu GPS mà là theo ý tưởng thiết kế của GPS. Vì vậy, chương trước được trình bày theo thứ tự sau đây. Các vị trí người sử dụng có thể được tìm thấy từ các vị trí được biết đến ít nhất bốn vệ tinh và các khoảng cách với họ. . | Fundamentals of Global Positioning System Receivers A Software Approach James Bao-Yen Tsui Copyright 2000 John Wiley Sons Inc. Print ISBN 0-471-38154-3 Electronic ISBN 0-471-20054-9 CHAPTER NINE GPS Software Receivers 9.1 INTRODUCTION This chapter can be considered as a summary of all the previous chapters. As mentioned in Chapter 1 this book does not follow the signal path of a GPS receiver but rather follows the design concept of the GPS. Therefore the previous chapters are presented in the following order. The user position can be found from the known positions of at least four satellites and the distances to them. In Chapters 2 to 4 the satellite constellation and the earth-centered earth-fixed coordinate system are introduced and the equations to calculate the user position are presented. The structure of the GPS signal and the acquisition and tracking of the signal are discussed in Chapters 5 7 and 8 respectively. Although this approach should give a better understanding of the overall concepts associated with GPS the discussion may not flow smoothly from a receiver design perspective. In this chapter the GPS receiver is discussed following the actual signal flow through the receiver. The input signal will be digitized first followed by acquisition and tracking. Once the tracking is achieved the output will be converted into navigation data through subframe matching and parity checking. From the subframes the ephemeris data such as the week number can be found. The position of the satellite can be determined from the ephemeris data. The pseudoranges between the receiver and the satellites can also be determined. Once all the necessary information is obtained satellite positions and the user position can be calculated. Finally the user position is put in the desired coordinate system. The presentation in this chapter follows this order which is shown in Figure 1.1. The block adjustment of synchronized signal BASS is used for the tracking program. The .