17057205182601000000 TLFeBOOK Introduction to GPS The Global Positioning System TLFeBOOK For a complete listing of the Artech House Mobile Communications Series, turn to the back of this book. TLFeBOOK Introduction to GPS The Global Positioning System Ahmed El-Rabbany Artech House Boston London www.com TLFeBOOK Library of Congress Cataloging-in-Publication Data El-Rabbany, Ahmed. Introduction to GPS: the Global Positioning System/Ahmed El-Rabbany.(Artech House mobile communications series) Includes bibliographical references and index. Global Postioning System.285dc21 2001055249 British Library Cataloguing in Publication Data El-Rabbany, Ahmed Introduction to GPS: the global positioning system/Ahmed El-Rabbany.
Global Positioning System I.045 ISBN 1-58053-183-0 Cover design by Yekatarina Ratner © 2002 ARTECH HOUSE, INC. 685 Canton Street Norwood, MA 02062 All rights reserved. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechani- cal, including photocopying, recording, or by any information storage and retrieval sys- tem, without permission in writing from the publisher.
All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Artech House cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. International Standard Book Number: 1-58053-183-0 Library of Congress Catalog Card Number: 2001055249 10 9 8 7 6 5 4 3 2 1 TLFeBOOK TLFeBOOK To the people who made significant contributions to my life My parents, my wife, and my children TLFeBOOK Contents Preface.
xv 1 Introduction to GPS .1 Overview of GPS.3 GPS satellite generations .4 Current GPS satellite constellation .6 GPS: The basic idea .7 GPS positioning service .8 Why use GPS?. 10 References · · · · · · · · · · · · · · · · · · · · · · · · 11 vii TLFeBOOK viii Introduction to GPS 2 GPS Details.1 GPS signal structure .3 Types of GPS receivers .6 Carrier-phase measurements .8 Linear combinations of GPS observables. 23 References · · · · · · · · · · · · · · · · · · · · · · · · 25 3 GPS Errors and Biases .1 GPS ephemeris errors .3 Satellite and receiver clock errors .5 Antenna-phase-center variation .6 Receiver measurement noise .9 Satellite geometry measures .10 GPS mission planning .11 User equivalent range error. 44 References · · · · · · · · · · · · · · · · · · · · · · · 44 4 Datums, Coordinate Systems, and Map Projections .1 What is a datum? .2 Geodetic coordinate system .1 Conventional Terrestrial Reference System .2 The WGS 84 and NAD 83 systems .3 What coordinates are obtained with GPS? .1 Transverse Mercator projection.
56 TLFeBOOK Contents ix 4.2 Universal transverse Mercator projection.3 Modified transverse Mercator projection .4 Lambert conical projection .5 Stereographic double projection .6 Marine nautical charts .7 Local arbitrary mapping systems. 65 References · · · · · · · · · · · · · · · · · · · · · · · · 66 5 GPS Positioning Modes .1 GPS point positioning .2 GPS relative positioning .3 Static GPS surveying .5 Stop-and-go GPS surveying .7 Real-time differential GPS .8 Real time versus postprocessing. 81 References · · · · · · · · · · · · · · · · · · · · · · · · 83 6 Ambiguity-Resolution Techniques .1 Antenna swap method .2 On-the-fly ambiguity resolution. 88 References · · · · · · · · · · · · · · · · · · · · · · · · 90 7 GPS Data and Correction Services .2 DGPS radio beacon systems .3 Wide-area DGPS systems .4 Multisite RTK system.
98 References · · · · · · · · · · · · · · · · · · · · · · · · 99 TLFeBOOK x Introduction to GPS 8 GPS Standard Formats .2 NGS-SP3 format.3 RTCM SC-104 standards for DGPS services. 112 References · · · · · · · · · · · · · · · · · · · · · · · 115 9 GPS Integration .1 GPS/GIS integration .2 GPS/LRF integration .3 GPS/dead reckoning integration .4 GPS/INS integration .5 GPS/pseudolite integration .6 GPS/cellular integration. 125 References · · · · · · · · · · · · · · · · · · · · · · · 127 10 GPS Applications .1 GPS for the utilities industry .2 GPS for forestry and natural resources .3 GPS for precision farming .4 GPS for civil engineering applications .5 GPS for monitoring structural deformations .6 GPS for open-pit mining.7 GPS for land seismic surveying .8 GPS for marine seismic surveying .9 GPS for airborne mapping .10 GPS for seafloor mapping .11 GPS for vehicle navigation .12 GPS for transit systems .13 GPS for the retail industry.14 GPS for cadastral surveying. 150 References · · · · · · · · · · · · · · · · · · · · · · 151 TLFeBOOK Contents xi 11 Other Satellite Navigation Systems .1 GLONASS satellite system .2 Chinese regional satellite navigation system (Beidou system) .4 Future European global satellite navigation system 11.
158 References · · · · · · · · · · · · · · · · · · · · · · · 159 Appendix A GPS Accuracy and Precision Measures. 161 Reference · · · · · · · · · · · · · · · · · · · · · · · 162 Appendix B Useful Web Sites .1 GPS/GLONASS/Galileo information and data. 165 About the Author. 169 TLFeBOOK TLFeBOOK Preface The idea of writing an easy-to-read, yet complete, GPS book evolved dur- ing my industrial employment term during the period from 1996 to 1997.
My involvement in designing and providing short GPS courses gave me the opportunity to get direct feedbacks from GPS users with a wide variety of expertise and background. One of the most difficult tasks, which I encoun- tered, was the recommendation of an appropriate GPS reference book to the course attendees. Giving the fact that the majority of the GPS users are faced with a very tight time, it was necessary that the selected GPS book be complete and easy-to-read. Such a book did not exist.
Initially, I developed the vugraphs, which I used in the delivery of the short GPS courses. I then modified the vugraphs several times to accom- modate not only the various types of GPS users but also my undergraduate students at both the University of New Brunswick and Ryerson University. The modified vugraphs were then used as the basis for this GPS book. I tried to address all aspects of GPS in a simple manner, avoiding any mathe- matics.
The book also addresses more recent issues such as the moderniza- tion of GPS and the proposed European satellite navigation system known as Galileo. As well, the book emphasizes GPS applications, which will bene- fit not only the GPS users but also the GPS marketing and sales personnel. xiii TLFeBOOK xiv Introduction to GPS Chapter 1 of the book introduces the GPS system and its components. Chapter 2 examines the GPS signal structure, the GPS modernization, and the key types of the GPS measurements.
An in-depth discussion of the errors and biases that affect the GPS measurements, along with suggestions on how to overcome them, is presented in Chapter 3. Datums, coordinate systems, and map projections are discussed in a simple manner in Chapter 4, offering a clear understanding of this widely misunderstood area. Chap- ters 5 and 6 address the various modes of GPS positioning and the issue of the ambiguity resolution of the carrier-phase measurements. The various GPS services available on the market and the standard formats used for the various types of GPS data are presented in Chapters 7 and 8.
Chapter 9 focuses on the integration of the GPS with other systems. The GPS applica- tions in the various fields are given in Chapter 10. The book ends with Chapter 11, which covers the other satellite navigation systems developed or proposed in different parts of the world. TLFeBOOK Acknowledgments I would like to extend my appreciation to Dr.
Alfred Kleusberg, Dr. Naser El-Sheimy, and Dr. David Wells for reviewing and/or commenting on the earlier version of the manuscript. xv TLFeBOOK TLFeBOOK Introduction to GPS 1 The Global Positioning System (GPS) is a satellite-based navigation system that was developed by the U.
Department of Defense (DoD) in the early 1970s. Initially, GPS was developed as a military system to fulfill U. mili- tary needs. However, it was later made available to civilians, and is now a dual-use system that can be accessed by both military and civilian users [1].
GPS provides continuous positioning and timing information, any- where in the world under any weather conditions. Because it serves an unlimited number of users as well as being used for security reasons, GPS is a one-way-ranging (passive) system [2]. That is, users can only receive the satellite signals. This chapter introduces the GPS system, its components, and its basic idea.1 Overview of GPS GPS consists, nominally, of a constellation of 24 operational satellites.
This constellation, known as the initial operational capability (IOC), was com- pleted in July 1993. The official IOC announcement, however, was made on December 8, 1993 [3]. To ensure continuous worldwide coverage, GPS 1 TLFeBOOK 2 Introduction to GPS satellites are arranged so that four satellites are placed in each of six orbital planes (Figure 1. With this constellation geometry, four to ten GPS sat- ellites will be visible anywhere in the world, if an elevation angle of 10° is considered.
As discussed later, only four satellites are needed to provide the positioning, or location, information. GPS satellite orbits are nearly circular (an elliptical shape with a maxi- mum eccentricity is about 0.01), with an inclination of about 55° to the equator. The semimajor axis of a GPS orbit is about 26,560 km (i., the sat- ellite altitude of about 20,200 km above the Earths surface) [4]. The corre- sponding GPS orbital period is about 12 sidereal hours (~11 hours, 58 minutes).
The GPS system was officially declared to have achieved full operational capability (FOC) on July 17, 1995, ensuring the availability of at least 24 operational, nonexperimental, GPS satellites. In fact, as shown in Section 1.4, since GPS achieved its FOC, the number of satellites in the GPS constellation has always been more than 24 operational satellites.2 GPS segments GPS consists of three segments: the space segment, the control segment, and the user segment (Figure 1. The space segment consists of the 24-satellite constellation introduced in the previous section. Each GPS sat- ellite transmits a signal, which has a number of components: two sine waves (also known as carrier frequencies), two digital codes, and a naviga- tion message.
The codes and the navigation message are added to the carri- ers as binary biphase modulations [5]. The carriers and the codes are used mainly to determine the distance from the users receiver to the GPS L-band antenna Solar panel S-band antenna Figure 1. TLFeBOOK Introduction to GPS 3 Space segment GPS signal Download (L-band) Upload (S-band) Control segment User segment Figure 1. The navigation message contains, along with other inform- ation, the coordinates (the location) of the satellites as a function of time.
The transmitted signals are controlled by highly accurate atomic clocks onboard the satellites. More about the GPS signal is given in Chapter 2. The control segment of the GPS system consists of a worldwide net- work of tracking stations, with a master control station (MCS) located in the United States at Colorado Springs, Colorado.