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

Accurately determining one's position has been a recurrent problem in history [1]. It even precedes the first deep-sea navigation attempts of ancient civilizations and reaches the present time with the issue of legal mandates for the location identification of emergency calls in cellular networks and the emergence of location-based services. The science and technology for positioning and navigation has experienced a dramatic evolution [2]. The observation of celestial bodies for navigation purposes has been replaced today by the use of electromagnetic waveforms emitted from reference sources [3].

Challenges in Indoor Global Navigation Satellite Systems: Unveiling its core features in signal processing

Indoor localization technologies hold promise for many ambient intelligence applications, including in-situ navigational assistance for individuals with wayfinding difficulties. Given that the literature on indoor localization is vast and spans many different disciplines, we conducted a comprehensive review of the dominant technologies. We propose a taxonomy of localization technologies on the basis of the measured physical quantity. In particular, we identified, radio frequency, photonic, sonic and inertial localization technologies as leading solutions in the field. For each selected technology, the fundamental scientific mechanisms for localization are explained, key recent literature appraised and the merits and limitations are discussed. Recommendations are made regarding the creation of context-aware systems that can be used to enhance a user's topographical orientation skills.

/pdf/a-review-of-indoor-localization-technologies-towards-3d1oih5k86.pdf

A Review of Indoor Localization Technologies: towards Navigational Assistance for Topographical Disorientation

It has been considered a fact that GPS performs too poorly inside buildings to provide usable indoor positioning. We analyze results of a measurement campaign to improve on the understanding of indoor GPS reception characteristics. The results show that using state-of-the-art receivers GPS availability is good in many buildings with standard material walls and roofs. The measured root mean squared 2D positioning error was below five meters in wooden buildings and below ten meters in most of the investigated brick and concrete buildings. Lower accuracies, where observed, can be linked to either low signal-to-noise ratios, multipath phenomena or bad satellite constellation geometry. We have also measured the indoor performance of embedded GPS receivers in mobile phones which provided lower availability and accuracy than state-of-the-art ones. Finally, we consider how the GPS performance within a given building is dependent on local properties like close-by building elements and materials, number of walls, number of overlaying stories and surrounding buildings.

/pdf/indoor-positioning-using-gps-revisited-1wi4f7aa9u.pdf

Indoor positioning using GPS revisited

AB Purpose: The objective of this study is to assess validity of the personal activity location measurement system (PALMS) for deriving time spent walking/running, bicycling, and in vehicle, using SenseCam (Microsoft, Redmond, WA) as the comparison. Methods: Forty adult cyclists wore a Qstarz BT-Q1000XT GPS data logger (Qstarz International Co., Taipei, Taiwan) and SenseCam (camera worn around the neck capturing multiple images every minute) for a mean time of 4 d. PALMS used distance and speed between global positioning system (GPS) points to classify whether each minute was part of a trip (yes/no), and if so, the trip mode (walking/running, bicycling, or in vehicle). SenseCam images were annotated to create the same classifications (i.e., trip yes/no and mode). Contingency tables (2 x 2) and confusion matrices were calculated at the minute level for PALMS versus SenseCam classifications. Mixed-effects linear regression models estimated agreement (mean differences and intraclass correlation coefficients) between PALMS and SenseCam with regard to minutes/day in each mode. Results: Minute-level sensitivity, specificity, and negative predictive value were >=88%, and positive predictive value was >=75% for non-mode-specific trip detection. Seventy-two percent to 80% of outdoor walking/running minutes, 73% of bicycling minutes, and 74%-76% of in-vehicle minutes were correctly classified by PALMS. For minutes per day, PALMS had a mean bias (i.e., amount of over or under estimation) of 2.4-3.1 min (11%-15%) for walking/running, 2.3-2.9 min (7%-9%) for bicycling, and 4.3-5 min (15%-17%) for vehicle time. Intraclass correlation coefficients were >=0.80 for all modes. Conclusions: PALMS has validity for processing GPS data to objectively measure time spent walking/running, bicycling, and in vehicle in population studies. Assessing travel patterns is one of many valuable applications of GPS in physical activity research that can improve our understanding of the determinants and health outcomes of active transportation as well as its effect on physical activity.

/pdf/validity-of-palms-gps-scoring-of-active-and-passive-travel-4xkpemtc4r.pdf

Validity of PALMS GPS scoring of active and passive travel compared with SenseCam

Ionospheric scintillations cause RF signal amplitude fading and phase variations as GPS satellite signals pass through the ionosphere. This is a particular concern for GPS operations in high latitude regions, such as Canada, where scintillations are associated with strong aurora – effects which persist even during solar minimum. In general, scintillations can cause degraded receiver tracking performance and, in extreme cases, loss of navigation capabilities entirely. Such effects are an issue for reliable GPS operations in the northern United States and Canada. The University of Calgary currently operates the Canadian GPS Network for Ionosphere Monitoring (CANGIM), which makes scintillations observations at various latitudes in the auroral and sub-auroral regions. These measurements are used to characterize high-latitude scintillation effects, and develop models for assessing GPS receiver performance in the presence of such effects. The focus of this paper is a study of the effects of ionospheric scintillation on GPS signals, based on a GPS software receiver developed at University of Calgary. This study consists of several components: simulating ionospheric scintillation effects on L1 using an intermediate frequency (IF) GPS software signal simulator, investigating phase lock loop (PLL) performance under scintillation conditions using a software receiver, and developing improved tracking loop models to minimize phase errors and loss of signal lock during scintillation events. Results indicate that PLL performance is degraded for moderate to severe scintillations, with loss of lock occurring for narrow bandwidths. By employing a fast adaptive bandwidth approach, reliable signal tracking can be achieved.

Investigating the Impact of Ionospheric Scintillation using a GPS Software Receiver

High-sensitivity GPS and assisted GPS are being extensively researched as methods to improve positioning indoors, where weak, multipath-affected signals are often difficult or impossible to use. To improve knowledge of indoor GPS behavior, this paper presents details of a raw GPS processing technique that enables extremely long coherent integrations, thereby providing extremely high detection sensitivity for indoor signals. The technique is used to evaluate signal characteristics in a pair of datasets gathered indoors, with carrier-to-noise density ratios as much as 40 dB or more below nominal open-sky signals. Results show that weak signals such as these can be used to provide reasonably accurate positioning if a sufficient number of signals can be detected to ensure good positioning geometry. Signal degradations caused by multipath are shown to be less damaging to posi- tion than the loss of availability caused by low signal strength. In addition, the high-sensitivity techniques based on precise tracking loop control demonstrate the potential for improved high-sensitivity GPS-based technologies using ultra-tight integration with additional sensors.

Investigating GPS signals indoors with extreme high-sensitivity detection techniques

Differential combining for acquiring weak GPS signals

Recent attempts to enhance GPS performance in weaksignal environments have focused on high-sensitivity GPS (HSGPS) and Assisted GPS (AGPS). High sensitivity can be realized in a stand-alone mode by using long noncoherent integration times with relatively short coherent accumulations of between 1 and 20 ms. AGPS further enables weak-signal acquisition by narrowing code and frequency search spaces to reduce time to first fix (TTFF), and by potentially providing navigation data bits to allow long coherent integration without suffering the effects of 180° phase transitions. Major problems remaining with HSGPS and AGPS techniques include the additional system complexity required to provide assistance data, the limiting effect of local oscillator instability, and the major losses incurred by squaring weak signals for non-coherent integration techniques. A number of differential signal processing schemes have been proposed to address some of these issues. These schemes use the known properties of CDMA spreading codes to largely eliminate some of these issues, offering the potential for enhanced sensitivity, TTFF, or both, in systems with lower complexity than AGPS requires. This paper examines a set of differential processing schemes designed for the GPS L1 C/A signal both theoretically and with live GPS data. The results show benefits and limitations to all three techniques as compared with standard processing techniques. Suitable receiver applications for the various techniques are considered.

Differential Signal Processing Schemes for Enhanced GPS Acquisition

Given the demanding computational requirements of software-based GPS receivers, high data processing efficiency is required to obtain real-time performance. There are two basic approaches to accomplish this: reducing the number of computations required, or improving the efficiency with which the computations are carried out. This paper takes the latter approach, primarily by using the MMX technology available on x86-compatible processors to more rapidly perform the Doppler removal and code correlation computations. Other computational saving methods are also described. Using this approach, computational improvements of greater than 70% are realized over the standard (integer math) implementation. Initial results indicate that tracking performance of the software receiver is reasonable and that position and velocity accuracies are at the meter and decimeter per second level, respectively. INTRODUCTION A typical GPS software receiver performs the entire baseband signal processing in the software module. This allows developers to modify and test new algorithms without making any changes to the hardware. Also, expanding a GPS software receiver in order to add support for new signal structures is easier and cheaper compared to traditional receivers. This is an appealing characteristic since we will see the arrival of many new signals such as L2C and L5 in the near future. Doppler removal and correlation of GPS signal requires millions of complex operations in a second, the execution of which is governed by both a processor’s speed and the availability of GPS data samples. If a software receiver operates slower than the rate required to process incoming data, it can lose lock on the signal and never track it properly. Moore’s law states that the number of transistors and resistors on a chip doubles every 18 months. In simple terms, the computational power available to us approximately doubles every 18 month. This will enable us to develop a multi-channel GPS receiver on low-end general purpose processors much more easily in the future. The PLAN (Position, Location And Navigation) Group developed its first software receiver (GNSS_SoftRx™) during the past three years. The post-mission version has already been used by numerous PLAN Group students for many research projects (Ma et al 2004, Skone et al 2005, Zheng & Lachapelle 2005). The current work focuses on expansion and optimization of this receiver in order to gain better performance, with

Robert Watson

Papers

Investigating the Impact of Ionospheric Scintillation using a GPS Software Receiver

Investigating GPS signals indoors with extreme high-sensitivity detection techniques

Differential combining for acquiring weak GPS signals

Differential Signal Processing Schemes for Enhanced GPS Acquisition

Implementation and Testing of a Real-Time Software-Based GPS Receiver for x86 Processors