Fundamentals of Satellite Navigation. GPS Systems Segments. GPS Satellite Signal Characteristics and Message Formats. Satellite Signal Acquisitions and Tracking. Effects of RF Interference on GPS Satellite Signal Receiver Tracking. Performance of Standalone GPS. Differential GPS. Integration of GPS with other Sensors. Galileo. The Russian GLONASS, Chinese Bediou, and Japanese QZSS Systems. GNSS Markets and Applications.

Understanding GPS : principles and applications

Navigation systems engineering is a red-hot area. More and more technical professionals are entering the field and looking for practical, up-to-date engineering know-how. This single-source reference answers the call, providing both an introduction to overall systems operation and an in-depth treatment of architecture, design, and component integration. This book explains how satellite, on-board, and other navigation technologies operate, and it gives practitioners insight into performance issues such as processing chains and error sources. Providing solutions to systems designers and engineers, the book describes and compares different integration architectures, and explains how to diagnose errors. Moreover, this hands-on book includes appendices filled with terminology and equations for quick referencing.

Principles of GNSS, Inertial, and Multi-Sensor Integrated Navigation Systems

This newly revised and greatly expanded edition of the popular Artech House book Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems offers you a current and comprehensive understanding of satellite navigation, inertial navigation, terrestrial radio navigation, dead reckoning, and environmental feature matching . It provides both an introduction to navigation systems and an in-depth treatment of INS/GNSS and multisensor integration. The second edition offers a wealth of added and updated material, including a brand new chapter on the principles of radio positioning and a chapter devoted to important applications in the field. Other updates include expanded treatments of map matching, image-based navigation, attitude determination, acoustic positioning, pedestrian navigation, advanced GNSS techniques, and several terrestrial and short-range radio positioning technologies. The book shows you how satellite, inertial, and other navigation technologies work, and focuses on processing chains and error sources. In addition, you get a clear introduction to coordinate frames, multi-frame kinematics, Earth models, gravity, Kalman filtering, and nonlinear filtering. Providing solutions to common integration problems, the book describes and compares different integration architectures, and explains how to model different error sources. You get a broad and penetrating overview of current technology and are brought up to speed with the latest developments in the field, including context-dependent and cooperative positioning. DVD Included: Features eleven appendices, interactive worked examples, basic GNSS and INS MATLAB simulation software, and problems and exercises to help you master the material.

Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems, Second Edition

This second edition of Dr. Grove's book (the original was published in 2008) could arguably be considered a new work. At just under 1,000 pages (including the 11 appendices on the DVD), the second edition is 80% longer than the original. Frankly, the word "book" hardly seems adequate, considering the wide range of topics covered. "Mini-encyclopedia" seems more appropriate. The hardcover portion of the book comprises 18 chapters, and the DVD includes the aforementioned appendices plus 20 fully worked examples, 125 problems or exercises (with answers), and MATLAB routines for the simulation of many of the algorithms discussed in the main text. Here is a brief overview of the contents: ▸ Chapters 1–3: an overview of the diversity of positioning techniques and navigation systems; fundamentals of coordinate frames, kinematics and earth models; introduction to Kaiman filtering ▸ Chapters 4–6: inertial sensors, inertial navigation, and lower-cost dead reckoning systems ▸ Chapters 7–12: principles of radio positioning, short-, medium-, and long-range radio navigation, as well as extensive coverage of global navigation satellite systems (GNSS) ▸ Chapter 13: environmental feature matching. ▸ Chapters 14–16: various integration topics, including inertial navigation system (INS)/GNSS integration, alignment, zero-velocity updates, and multisensor integration ▸ Chapter 17: fault detection. ▸ Chapter 18: applications and trends. In summary, this book is an excellent reference (with numerous nuggets of wisdom) that should be readily handy on the shelf of every practicing navigation engineer. In the hands of an experienced instructor, the book will also serve students as a great textbook. However, the lack of examples integrated in the main text makes it difficult for the book to serve as a self-study guide for those that are new to the field.

Principles of GNSS, inertial, and multisensnr integrated navigation systems, 2nd edition [Book review]

A subscriber unit for use in a multiple access spread-spectrum communication system includes a spread spectrum radio interface, responsive to a rate function signal from a base station, and first and second despreaders. The base station assigns the rate function spread-spectrum message channels and the first despreader recovers and modifies an information signal one of the spread spectrum message channels. The information channel mode is then modified for processing by the second despreader, with the second despreader supporting a different information signal rate. The subscriber unit has a capability of communicating with a dynamically changing a transmission rate of an information signal which includes multiple spread spectrum message channels. The system includes a closed loop power control system for maintaining a minimum system transmit power level for a radio carrier station and the subscriber units, and system capacity management for maintaining a maximum number of active subscriber units for improved system performance.

Code division multiple access (CDMA) communication system

The reduction of multipath biases on GPS measurements has traditionally been achieved through innovative antenna design, such as choke ring ground planes, and careful antenna site selection. These methods, although effective, are not always practical, especially in a kinematic environment. The implementation of Narrow Correlator mspacing design in GPS receiver code tracking loops has greatly reduced the multipath bias and the measurement noise on C/A code pseudorange measurements. Even with these advancements the bias due to multipath is still dominant in GPS position calculations. This paper introduces a new tracking loop which takes full advantage of the Narrow CorrelatorT5t spacing design, but in addition, is much more resistant to multipath effects on the correlation function and thereby reduces the multipath bias on the pseudorange measurements. The theory behind this new tracking loop design is presented along with its implementation into existing receiver hardware. Test results from a prototype receiver are presented. They show a 25 to 50 percent reduction of multipath error effects in the DGPS position solution as compared to a standard narrow correlator receiver.

A Practical Approach to the Reduction of Pseudorange Multipath Errors in a Ll GPS Receiver

A receiver for pseudorandom noise (PRN) encoded signals consisting of a sampling circuit, multiple carrier and code synchronizing circuits, and multiple digital correlators. The sampling circuit provides digital samples of a received composite signal to each of the several receiver channel circuits. The synchronizing circuits are preferably non-coherent, in the sense that they track any phase shifts in the received signal and adjust the frequency and phase of a locally generated carrier reference signal accordingly, even in the presence of Doppler or ionospheric distortion. The multiple correlators in each channel correlate the digital samples with locally generated PRN codes having multiple offsets, to produce a plurality of correlation signals. The plurality of correlation signals are fed to a parameter estimator, from which the delay and phase parameters of the direct path signal, as well as any multipath signals, may be estimated, and from which a range measurement may be corrected.

Pseudorandom noise ranging receiver which compensates for multipath distortion by making use of multiple correlator time delay spacing

When using narrow correlator spacing in a GPS receiver, the C/A-code tracking errors are on the order of a decimeter. In the presences of multipath signals, tracking errors can be on the order of a few meters. In many differential GPS applications, multipath is the most significant source of error. In a previous paper, the authors demonstrated that it is possible to reduce multipath errors greatly by using the Multipath Estimating Delay Lock Loop (MEDLL). Since then, MEDLL has been implemented into a multichannel receiver that calculates the pseudorange multipath errors in real time.



This paper reviews the multipath problem in the GPS receiver and the theory of the MEDLL. Two experiments carried out to evaluate the MEDLL are described. First, measurements were collected simultaneously with the MEDLL receiver and a standard NovAtel narrow-correlator receiver over a short baseline. Second, the same receivers were connected to a GPS signal simulator so a multipath signal could be introduced in a controlled enviroment.

Performance Evaluation of the Multipath Estimating Delay Lock Loop

Multipath is a major source of error in high precision Global Positioning System (GPS) static and kinematic differential positioning. Multipath accounts for most of the total error budget in carrier phase measurements in a spacecraft attitude determination system. It is a major concern in reference stations, such as in Local Area Augmentation Systems (LAAS), whereby corrections generated by a reference station, which are based on multipath corrupted measurements, can significantly influence the position accuracy of differential users. Code range, carrier phase, and signal-to-noise (SNR) measurements are all affected by multipath, and the effect is spatially correlated within a small area. In order to estimate and remove code and carrier phase multipath, a system comprising a cluster of five GPS receivers and antennas is used at a reference station location. The spatial correlation of the receiver data, and the known geometry among the antennas, are exploited to estimate multipath for each satellite in each antenna in the system. Generic receiver code and carrier tracking loop discriminator functions are analyzed, and relationships between receiver data, such as code range, carrier phase, and SNR measurements, are formulated and related to various multipath parameters. A Kalman filter is described which uses a combination of the available information from the antennas (receivers) in the multiantenna cluster to estimate various multipath parameters. From the multipath parameters, the code range and carrier phase multipath is estimated and compensated. The technique is first tested on simulated data in a controlled multipath environment. Results are then presented using field data and show a significant reduction in multipath error.

GPS code and carrier multipath mitigation using a multiantenna system

In single frequency (Ll) GPS receivers, multipath is the
dominant error source in differential carrier phase and
pseudorange measurements. Consequently, it is the
dominant error effecting DGPS positioning accuracy.
The Multipath Estimating Delay Lock Loop (MEDLL) is
a method for mitigating the effects due to multipath
within the receiver tracking loops. The MEDLL does
this by separating the incoming signal into its line-of-
sight and multipath components. Using the line-of-sight
component, the unbiased measurements of code and
carrier phase can be made.
In previous papers, the authors have demonstrated
MEDLL performance in mitigating the effects of
multipath on C/A code pseudorange measurements.
Also, they have shown that it is possible to use the
MEDLL derived parameters to calculate a multipath
error correction for the carrier phase measurements.
This carrier phase multipath correction has now been
implemented in NovAtel’s MEDLL receiver.
Using a GPS signal simulator, the carrier phase
performance of the MEDLL receiver for a single
multipath and a multiple multipath case was compared to
a standard phase lock loop. The results showed the
MEDLL receiver was able to substantially reduce the
carrier phase multipath errors as compared to a standard
NovAtel receiver.

Patrick C. Fenton

Papers

A Practical Approach to the Reduction of Pseudorange Multipath Errors in a Ll GPS Receiver

Pseudorandom noise ranging receiver which compensates for multipath distortion by making use of multiple correlator time delay spacing

Performance Evaluation of the Multipath Estimating Delay Lock Loop

GPS code and carrier multipath mitigation using a multiantenna system

L1 Carrier Phase Multipath Error Reduction Using MEDLL Technology