El-Rabbany A. Introduction to GPS
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4.5.2 Universal transverse Mercator projection..........57
4.5.3 Modified transverse Mercator projection ..........59
4.5.4 Lambert conical projection ...............60
4.5.5 Stereographic double projection .............61
4.6 Marinenauticalcharts...................62
4.7 Local arbitrary mapping systems ..............64
4.8 Heightsystems......................65
References ························66
5 GPS Positioning Modes ................69
5.1 GPS point positioning ...................70
5.2 GPS relative positioning ..................71
5.3 Static GPS surveying ...................72
5.4 Fast(rapid)static.....................74
5.5 Stop-and-go GPS surveying ................75
5.6 RTKGPS........................77
5.7 Real-time differential GPS .................78
5.8 Real time versus postprocessing ...............80
5.9 Communication(radio)link................81
References ························83
6 Ambiguity-Resolution Techniques...........85
6.1 Antenna swap method ...................87
6.2 On-the-fly ambiguity resolution...............88
References ························90
7 GPS Data and Correction Services ...........91
7.1 Dataservice.......................92
7.2 DGPS radio beacon systems ................94
7.3 Wide-areaDGPSsystems .................95
7.4 Multisite RTK system ...................98
References ························99
Contents ix
TEAMFLY
Team-Fly
®
8 GPS Standard Formats ................101
8.1 RINEXformat......................101
8.2 NGS-SP3format.....................105
8.3 RTCM SC-104 standards for DGPS services .........108
8.4 NMEA 0183 format ...................112
References ·······················115
9 GPS Integration ...................117
9.1 GPS/GISintegration...................117
9.2 GPS/LRFintegration...................118
9.3 GPS/dead reckoning integration ..............120
9.4 GPS/INSintegration...................121
9.5 GPS/pseudolite integration ................123
9.6 GPS/cellularintegration .................125
References ·······················127
10 GPS Applications ..................129
10.1 GPS for the utilities industry ...............129
10.2 GPS for forestry and natural resources ...........131
10.3 GPS for precision farming ................132
10.4 GPS for civil engineering applications ...........133
10.5 GPSformonitoringstructuraldeformations........134
10.6 GPS for open-pit mining.................135
10.7 GPS for land seismic surveying ..............138
10.8 GPS for marine seismic surveying .............139
10.9 GPS for airborne mapping ................140
10.10 GPS for seafloor mapping ................142
10.11 GPS for vehicle navigation ...............144
10.12 GPSfortransitsystems.................146
10.13 GPS for the retail industry................147
10.14 GPS for cadastral surveying ...............149
10.15 GPS stakeout (waypoint navigation) ...........150
References ······················151
x Introduction to GPS
11 Other Satellite Navigation Systems .........155
11.1 GLONASS satellite system ................155
11.2 Chinese regional satellite navigation system (Beidou system) . 157
11.3 Regional augmentations .................157
11.4 Future European global satellite navigation system
11.4 (Galileo system) ....................158
References ·······················159
Appendix A
GPS Accuracy and Precision Measures .........161
Reference ·······················162
Appendix B
Useful Web Sites ....................163
B.1 GPS/GLONASS/Galileo information and data ........163
B.2 GPS manufacturers ...................165
About the Author ....................167
Index...........................169
Contents xi
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
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.
xiv Introduction to GPS
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
1
Introduction to GPS
The Global Positioning System (GPS) is a satellite-based navigation system
that was developed by the U.S. Department of Defense (DoD) in the early
1970s. Initially, GPS was developed as a military system to fulfill U.S. 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.
1.1 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
satellites are arranged so that four satellites are placed in each of six orbital
planes (Figure 1.1). 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.e., 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.
1.2 GPS segments
GPS consists of three segments: the space segment, the control segment,
and the user segment (Figure 1.2) [5]. 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
2 Introduction to GPS
S-band antenna
L-band antenna
Solar panel
Figure 1.1 GPS constellation.