Introduction to GNSS
This chapter is a primer on global navigation satellite systems (GNSS s). It assumes no prior knowledge of the systems or how they work. All of the key concepts of satellite-based positioning, navigation, and timing (PNT ) are introduced with pointers to
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Richard B. Langley, Peter J.G. Teunissen, Oliver Montenbruck
This chapter is a primer on global navigation satellite systems (GNSSs). It assumes no prior knowledge of the systems or how they work. All of the key concepts of satellite-based positioning, navigation, and timing (PNT) are introduced with pointers to subsequent chapters for further details. The chapter begins with a history of PNT using satellites and then introduces the concept of positioning using measured ranges between a receiver and satellites. The basic observation equations are then described along with the associated error budgets. Subsequently, the various GNSSs now in operation and in development are briefly overviewed. The chapter concludes with a discussion of the relevance and importance of GNSS for science and society at large.
1.1
Early Satellite Navigation......................
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1.2 1.2.1 1.2.2 1.2.3 1.2.4 1.2.5
Concept of GNSS Positioning ................. Ranging Measurements ......................... Range-Based Positioning ...................... Pseudorange Positioning ....................... Precision of Position Solutions ............... GNSS Observation Equations ..................
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1.3 1.3.1 1.3.2
Modeling the Observations ................... Satellite Orbit and Clock Information ...... Atmospheric Propagation Delay..............
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1.4 1.4.1 1.4.2 1.4.3
Positioning Modes ............................... Precise Point Positioning ....................... Code Differential Positioning.................. Differential Carrier Phase .......................
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1.5 1.5.1 1.5.2 1.5.3
Current and Developing GNSSs .............. Global Navigation Satellite Systems ........ Regional Navigation Satellite Systems ..... Satellite-Based Augmentation Systems ...
16 16 18 19
1.6
GNSS for Science and Society at Large ....
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References.....................................................
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1.1 Early Satellite Navigation We will introduce the basic concepts of the Navstar Global Positioning System (GPS) and the other global navigation satellite systems (GNSSs) in operation and under development but it will be helpful if we first view them in a historical perspective. Determining the positions of points on the Earth’s surface using observations of distant objects has been carried out for hundreds of years. Reflecting mirrors on mountaintops gave way to using high-altitude flares and rockets. And, of course, celestial navigation using observations of the Sun, stars, and planets has been used for centuries. However, it was only with the dawning of the space age that it became possible to develop a global system for high accuracy positioning and navigation. Sometimes we refer to these systems as space-based systems. They can be broadly classified into optical techniques and radio techniques. Both kinds of system were pioneered in the late 1950s and 1960s.
Optical techniques are those techniques that utilize the visible part of the electromagnetic spectrum and in addition to astronomical positioning usin
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