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2008 | Buch

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GNSS — Global Navigation Satellite Systems

GPS, GLONASS, Galileo, and more

verfasst von: Dr. Bernhard Hofmann-Wellenhof, Dr. Herbert Lichtenegger, Dr. Elmar Wasle

Verlag: Springer Vienna

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

“GNSS - GPS, GLONASS, Galileo and more” is the extension of the scientific bestseller “GPS - Theory and Practice” to Global Navigation Satellite Systems (GNSS) and includes the Russian GLONASS, the European system Galileo, and additional systems.

The book refers to GNSS in the generic sense to describe the various existing reference systems for coordinates and time, the satellite orbits, the satellite signals, observables, mathematical models for positioning, data processing, and data transformation.

With respect to the individual systems GPS, GLONASS, Galileo and more, primarily the specific reference systems, services, the space and the control segment, as well as satellite signals are described. Furthermore, augmentations by space- and ground-based systems are discussed.

This book is a university-level introductory textbook and is intended to serve as a reference for students as well as for professionals and scientists in the fields of geodesy, surveying engineering, navigation, and related disciplines.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract

Since the dawn of civilization, man has looked to the heavens with awe searching for portentous signs. Some of these men became experts in deciphering the mystery of the stars and developed rules for governing life based upon their placement. The exact time to plant the crops was one of the events that was foretold by the early priest astronomers who in essence were the world’s first surveyors. Today, it is known that the alignment of such structures as the pyramids and Stonehenge was accomplished by celestial observations and that the structures themselves were used to measure the time of celestial events such as the vernal equinox.

2. Reference systems

Abstract

The basic equation which relates the range ϱ with the instantaneous position vector ϱ^s of a satellite and the position vector ϱ_r of the observing site reads

$$ \varrho = \left\| {\rho ^s - \rho _r } \right\|. $$

(2.1)

In Eq. (2.1), both vectors must be expressed in a uniform coordinate system. The definition of a three-dimensional Cartesian system requires a convention for the orientation of the axes and for the location of the origin.

3. Satellite orbits

Abstract

The applications of operational satellite methods depend substantially on knowing the satellite orbits. For single receiver positioning, an orbital error is highly correlated with the position error. In the case of baselines, relative orbital errors are approximately equal to relative baseline errors.

4. Satellite signals

Abstract

The different methods of satellite navigation are classified into passive and active as well as into one-way (uplink = earth-to-space; downlink = space-to-earth) and two-way ranging systems. Active systems require the user to emit signals. The three major GNSS (GPS, GLONASS, Galileo) are passive one-way downlink ranging systems. The satellites emit modulated signals that include the time of transmission to derive ranges as well as the modeling parameters to compute satellite positions. A three-layer model describes the emitted satellite signals best (Fig. 4.1).

5. Observables

Abstract

In concept, the satellite navigation observables are ranges which are deduced from measured time or phase differences based on a comparison between received signals and receiver-generated signals. Unlike the terrestrial electronic distance measurements, satellite navigation uses the “ one-way concept” where two clocks are involved, namely one in the satellite and the other in the receiver. Thus, the ranges are biased by satellite and receiver clock errors and, consequently, they are denoted as pseudoranges.

6. Mathematical models for positioning

Abstract

The code pseudorange at an epoch t can be modeled, cf. Eq. (5.2), by

$$ R_r^s (t) = \varrho _r^s (t) + c\Delta \delta _r^s (t). $$

(6.1)

Here, R _r ^s (t) is the measured code pseudorange between the observing receiver site r and the satellite s, the term ϱ _r ^s (t) is the geometric distance between the observing point and the satellite, and c is the speed of light. The last item to be explained is Δδ _r ^s (t). This clock bias represents the combined clock offsets of the receiver and the satellite clock with respect to system time, cf. Eq. (5.1).

7. Data processing

Abstract

Both the observables and the navigation message and additional information are generally stored in a binary (and receiver-dependent) format. The downloading of the data from the receiver is necessary before postprocessing can begin.

8. Data transformation

Abstract

From the user’s point of view, one official reference frame of GNSS would be desirable. For several reasons, the reality is far from this idealization: the reference frame of GPS is WGS-84, for GLONASS it is PE-90, and also Galileo with GTRF will have its own reference frame (see Sects. 9.2, 10.2, and 11.2, respectively). Nevertheless, the main property of these reference frames is the same; they are realized by a geocentric Cartesian coordinate system. Therefore, when using GNSS, the coordinates of terrestrial sites are obtained in the respective reference frame. The surveyor is not, usually, interested in coordinates of the terrestrial points referring to a global frame; rather, the results are preferred in a local coordinate frame either as geodetic (i.e., ellipsoidal) coordinates, as plane coordinates, or as vectors combined with other terrestrial data. Since the realization of the GNSS reference frame (WGS-84, PE-90, GTRF) is a geocentric system and the local system usually is not, certain transformations are required. The subsequent sections deal with the transformations most frequently used.

9. GPS

Abstract

The Global Positioning System is the responsibility of the Joint Program Office (JPO), a component of the Space and Missile Center at El Segundo, California. In 1973, the JPO was directed by the US Department of Defense (DoD) to establish, develop, test, acquire, and deploy a spaceborne positioning system. The present navigation system with timing and ranging (NAVSTAR) Global Positioning System (GPS) is the result of this initial directive.

10. Glonass

Abstract

The abbreviation GLONASS derives from the Russian “Global’ naya Navigatsionnaya Sputnikovaya Sistema”, translated to its English equivalent, this means Global Navigation Satellite System. In the mid 1970s, the former Union of Soviet Socialist Republics (USSR) initiated the development of GLONASS based on the experiences with the Doppler satellite system Tsikada. Following Polischuk et al. (2002), the Academician M.F. Reshetnev’s State Unitary Enterprise of Applied Mechanics has been the main contractor being responsible for the general development and implementation of the system. Moreover, the development and manufacturing of the satellites and their launch facilities and the corresponding control system belong to the tasks of this enterprise.

11. Galileo

Abstract

Europe early recognized the strategic, economic, social, and technological importance of satellite-based navigation. A European strategy and major actions in the field of satellite positioning and navigation have become necessary to establish trans-European networks in the fields of transport, telecommunications, and energy infrastructures in accordance with the European Community (EC) treaty (European Council 1994).

12. More on GNSS

Abstract

Satellite navigation systems are categorized into one-way and two-way ranging systems. One-way systems either measure ranges or range rates using signals sent from earth to space (uplink) or from space to earth (downlink). Considering twoway ranging systems, the signals travel the distance between user and satellite or vice versa two times. Some system concepts rely on signals sent from ground stations via satellites to the user and back again.

13. Applications

Abstract

No textbook can address all the GNSS applications, especially when users create new ones almost every day. Consequently, first the different products derived from satellite measurements are discussed. Then the data exchange between GNSS receivers and other system components is highlighted followed by performance enhancements to meet the stringent user requirements which can be achieved by integrating GNSS systems with other systems and technologies. Finally, a short introduction into the user segment is supplemented by selected applications.

14. Conclusion and outlook

Abstract

The future applications of GNSS are limited only by one’s imagination. For readers being not satisfied with this pretty general statement, a few more specific answers are given of five leading companies in an article on “The future of GNSS applications” published in the January/February 2007 issue of the GeoInformatics Magazine for Surveying, Mapping & GIS Professionals.

Backmatter

Titel: GNSS — Global Navigation Satellite Systems
verfasst von: Dr. Bernhard Hofmann-Wellenhof
Dr. Herbert Lichtenegger
Dr. Elmar Wasle
Verlag: Springer Vienna
Electronic ISBN: 978-3-211-73017-1
Print ISBN: 978-3-211-73012-6
DOI: https://doi.org/10.1007/978-3-211-73017-1

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Inhaltsverzeichnis

Frontmatter

1. Introduction

2. Reference systems

3. Satellite orbits

4. Satellite signals

5. Observables

6. Mathematical models for positioning

7. Data processing

8. Data transformation

9. GPS

10. Glonass

11. Galileo

12. More on GNSS

13. Applications

14. Conclusion and outlook

Backmatter

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