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Showing papers on "GNSS augmentation published in 2012"


Book
26 Oct 2012
TL;DR: In this paper, a survey of future inertial navigation concepts associated with the kalman filtering is presented. But this survey focuses on the future applications engineering activity activities and not on the current inertial navigator.
Abstract: Fundamentals of Inertial Navigation, Satellite-based Positioning and their Integration is an introduction to the field of Integrated Navigation Systems. It serves as an It emphasizes that a survey of future inertial navigation concepts associated with the kalman filtering. He has been active in discussing the necessary details inertial navigator. Accuracy an introduction to the material. The penn state's navigation systems engineers, as it is derived his background. Students new to the design and, several others. The concept of the future applications engineering activity fundamentals. The explanation of newton's second law, is a best navigation focusing on the practical. The classical techniques for the area theory as they apply to critical. It emphasizes the detection or other systems emphasizing gps ephemeris solution path loss. It works and gbas he has been an easy to real.

450 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used 3D building models to predict satellite visibility in urban canyons and evaluated the performance of current and future GNSS in London with decimetre-level accuracy.
Abstract: Positioning using the Global Positioning System (GPS) is unreliable in dense urban areas with tall buildings and/or narrow streets, known as ‘urban canyons’. This is because the buildings block, reflect or diffract the signals from many of the satellites. This paper investigates the use of 3-Dimensional (3-D) building models to predict satellite visibility. To predict Global Navigation Satellite System (GNSS) performance using 3-D building models, a simulation has been developed. A few optimized methods to improve the efficiency of the simulation for real-time purposes were implemented. Diffraction effects of satellite signals were considered to improve accuracy. The simulation is validated using real-world GPS and GLObal NAvigation Satellite System (GLONASS) observations. The performance of current and future GNSS in urban canyons is then assessed by simulation using an architectural city model of London with decimetre-level accuracy. GNSS availability, integrity and precision is evaluated over pedestrian and vehicle routes within city canyons using different combinations of GNSS constellations. The results show that using GPS and GLONASS together cannot guarantee 24-hour reliable positioning in urban canyons. However, with the addition of Galileo and Compass, currently under construction, reliable GNSS performance can be obtained at most, but not all, of the locations in the test scenarios. The modelling also demonstrates that GNSS availability is poorer for pedestrians than for vehicles and verifies that cross-street positioning errors are typically larger than along-street due to the geometrical constraints imposed by the buildings. For many applications, this modelling technique could also be used to predict the best route through a city at a given time, or the best time to perform GNSS positioning at a given location.

150 citations


Journal ArticleDOI
13 Jan 2012
TL;DR: The vastly broadened GNSS spectra, spread densely across 1146-1616 MHz, versus the narrow Global Positioning System (GPS) L1 and L2 bands, together with a constellation of over 100 Medium Earth Orbit (MEO) and Geostationary Earth Orbit
Abstract: Global Navigation Satellite System (GNSS) will in effect be fully deployed and operational in a few years, even with the delays in Galileo as a consequence of European Union's financial difficulties. The vastly broadened GNSS spectra, spread densely across 1146-1616 MHz, versus the narrow Global Positioning System (GPS) L1 and L2 bands, together with a constellation of over 100 Medium Earth Orbit (MEO) and Geostationary Earth Orbit (GEO) satellites versus GPS' 24 MEO satellites, are revolutionizing the design of GNSS receive antennas. For example, a higher elevation cutoff angle will be preferred. As a result, fundamental changes in antenna design, new features and applications, as well as cost structures are ongoing. Existing GNSS receive antenna technologies are reviewed and design challenges are discussed.

123 citations


Proceedings ArticleDOI
03 Jun 2012
TL;DR: A lightweight multipath detection algorithm which is based on dynamically built 3D environmental maps is proposed which is applied to a combined GPS and GLONASS system in combination with a loosely coupled integration of odometry measurements from the vehicle.
Abstract: Reliable knowledge of the ego position for vehicles is a crucial requirement for many automotive applications. In order to solve this problem for satellite-based localization in dense urban areas, multipath situations need to be handled carefully. This paper proposes a lightweight multipath detection algorithm which is based on dynamically built 3D environmental maps. The algorithm is evaluated with simulated and real-world data. Furthermore, it is applied to a combined GPS and GLONASS system in combination with a loosely coupled integration of odometry measurements from the vehicle.

97 citations


Journal ArticleDOI
07 Mar 2012-Sensors
TL;DR: An integrated camera/IMU/GNSS system based on the extended Kalman filter (EKF) is developed that provides accurate estimations and potentially outperforms the tightly coupled GNSS/ IMU integration in challenging environments with sparse GNSS observations.
Abstract: Low-cost MEMS-based IMUs, video cameras and portable GNSS devices are commercially available for automotive applications and some manufacturers have already integrated such facilities into their vehicle systems. GNSS provides positioning, navigation and timing solutions to users worldwide. However, signal attenuation, reflections or blockages may give rise to positioning difficulties. As opposed to GNSS, a generic IMU, which is independent of electromagnetic wave reception, can calculate a high-bandwidth navigation solution, however the output from a self-contained IMU accumulates errors over time. In addition, video cameras also possess great potential as alternate sensors in the navigation community, particularly in challenging GNSS environments and are becoming more common as options in vehicles. Aiming at taking advantage of these existing onboard technologies for ground vehicle navigation in challenging environments, this paper develops an integrated camera/IMU/GNSS system based on the extended Kalman filter (EKF). Our proposed integration architecture is examined using a live dataset collected in an operational traffic environment. The experimental results demonstrate that the proposed integrated system provides accurate estimations and potentially outperforms the tightly coupled GNSS/IMU integration in challenging environments with sparse GNSS observations.

71 citations


Journal ArticleDOI
TL;DR: The global navigation satellite system (GNSS) precise point positioning (PPP) concept is generalized to array-aided PPP (A-PPP), a measurement concept that uses GNSS data from multiple antennas in an array of known geometry to realize improved GNSS parameter estimation.
Abstract: In this paper, the global navigation satellite system (GNSS) precise point positioning (PPP) concept is generalized to array-aided PPP (A-PPP). A-PPP is a measurement concept that uses GNSS data, from multiple antennas in an array of known geometry, to realize improved GNSS parameter estimation (position, attitude, time and atmospheric delays). The concept is formulated such that it applies to each current and future multifrequency GNSS, stand-alone or in combination. A-PPP is made possible through solving a novel orthonormality-constrained multivariate (mixed) integer least-squares problem. It is shown that the integer matrix constraint is necessary to obtain a precise instantaneous attitude- and position solution, whereas the inclusion of the orthonormality constraint in the integer ambiguity objective function is essential to achieve high instantaneous probabilities of correct integer estimation. Different A-PPP applications are discussed, with their performances illustrated by means of empirical GPS results.

62 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a near real-time (NRT) high resolution water vapour distribution models based on GNSS observations delivered from Ground Base Augmentation Systems (GBAS) and ground meteorological data.
Abstract: . The near real-time (NRT) high resolution water vapour distribution models can be constructed based on GNSS observations delivered from Ground Base Augmentation Systems (GBAS) and ground meteorological data. Since 2008 in the territory of Poland, a GBAS system called ASG-EUPOS (Active Geodetic Network) has been operating. This paper addresses the problems concerning construction of the NRT model of water vapour distribution in the troposphere near Poland. The first section presents all available GNSS and ground meteorological stations in the area of Poland and neighbouring countries. In this section, data feeding scheme is discussed, together with timeline and time resolution. The high consistency between measured and interpolated temperature value is shown, whereas some discrepancy in the pressure is observed. In the second section, the NRT GNSS data processing strategy of ASG-EUPOS network is discussed. Preliminary results show fine alignment of the obtained Zenith Troposphere Delays (ZTDs) with reference data from European Permanent Network (EPN) processing center. The validation of NRT troposphere products against daily solution shows 15 mm standard deviation of obtained ZTD differences. The last section presents the first results of 2-D water vapour distribution above the GNSS network and application of the tomographic model to 3-D distribution of water vapour in the atmosphere. The GNSS tomography model, working on the simulated data from numerical forecast model, shows high consistency with the reference data (by means of standard deviation 4 mm km−1 or 4 ppm), however, noise analysis shows high solution sensitivity to errors in observations. The discrepancy for real data preliminary solution (measured as a mean standard deviation) between reference NWP data and tomography data was on the level of 9 mm km−1 (or 9 ppm) in terms of wet refractivity.

52 citations


Journal ArticleDOI
TL;DR: A newly developed GNSS carrier-phase ambiguity resolution method, which solves for the unknown number of integer cycles by exploiting the known placement of the GNSS antennas aboard the vessel and is tested against the most challenging scenario when processing GNSS data.
Abstract: Global Navigation Satellite System (GNSS) is a valuable technology for a large number of maritime applications. Other than providing the absolute positioning service, it aids many demanding applications, such as precise docking, formation of surface craft, autonomous vehicles, sinkage monitoring, etc. GNSS carrier-phase-based algorithms provide high-precision positioning solutions, but an integer number of cycles inherent to the observed signal have to be resolved. A newly developed GNSS carrier-phase ambiguity resolution method is tested. The new method solves for the unknown number of integer cycles by exploiting the known placement of the GNSS antennas aboard the vessel. The a priori information on the antennas baseline separation is employed as a hard constraint. A simplified (linearized) version of the method, suitable for large vessels, is also analyzed. The new method was tested against the most challenging scenario when processing GNSS data: single-frequency, single-epoch, unaided ambiguity resolution. Through different tests, the high performance of the new method is demonstrated: high fixing rate, large robustness, and short time-to-fix after initialization, cycle slips, and/or loss of locks. Considerations about the wide spectra of maritime applications are given, and a specific experiment is carried out to demonstrate the capabilities of the method for navigation in shallow waters.

51 citations


Journal ArticleDOI
TL;DR: The main innovations include the application of precise ionospheric corrections to facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation, and integrity monitoring.
Abstract: This paper summarizes the main results obtained during the development of an Enhanced Precise Point Positioning (EPPP) Global Navigation Satellite Systems multifrequency user algorithm. The main innovations include the application of precise ionospheric corrections to facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation, and integrity monitoring. The performance of the EPPP algorithm in terms of accuracy, convergence time, and integrity is demonstrated with actual GPS and simulated Galileo data. This can be achieved with very limited bandwidth requirements for EPPP users (less than 300 b/s for dual-frequency GPS data).

50 citations


Book
03 Feb 2012
TL;DR: Different GNSS applications are demonstrated and evaluated in hybrid positioning, multi-sensor integration, height system, Network Real Time Kinematic (NRTK), wheeled robots, and status and engineering surveying.
Abstract: Global Navigation Satellite System (GNSS) plays a key role in high precision navigation,positioning, timing, and scientific questions related to precise positioning. This is a highly precise, continuous, all-weather, and real-time technique. The book is devoted to presenting recent results and developments in GNSS theory, system, signal, receiver, method, and errors sources, such as multipath effects and atmospheric delays. Furthermore, varied GNSS applications are demonstrated and evaluated in hybrid positioning, multi-sensor integration, height system, Network Real Time Kinematic (NRTK), wheeled robots, and status and engineering surveying. This book provides a good reference for GNSS designers, engineers, and scientists, as well as the user market.

48 citations


Journal ArticleDOI
TL;DR: The Wide Area Real Time Kinematic (WARTK) as discussed by the authors is an augmentation system concept for multi-frequency users based on precise real-time ionospheric modeling, which is able to provide a high accuracy and integrity GNSS positioning service over continental areas using the infrastructure of a network of permanent ground monitor stations.
Abstract: [1] The Wide Area Real Time Kinematic (WARTK) is an augmentation system concept for multi-frequency users based on precise real-time ionospheric modeling It is able to provide a high accuracy and integrity GNSS positioning service over continental areas using the infrastructure of a network of permanent ground monitor stations, such as the European Geostationary Navigation Overlay Service (EGNOS) network of Ranging and Integrity Monitoring Stations (RIMS) in Europe In this way, it allows an additional benefit to be obtained from these reference stations, that is, the network has the potential to support two independent systems: a satellite-based augmentation system, such as EGNOS, and a high-precision positioning service, based on WARTK Indeed, thanks to the accuracy of the ionospheric corrections provided, WARTK users have available in real-time an extra constraint per satellite between the carrier phase ambiguities, which helps solve them quickly Once such ambiguities have been solved, the GNSS user obtains navigation accurate to within 20 cm at the 95th percentile (about 10 cm RMS) Moreover, this precise positioning is achieved in a few minutes (with two frequency signals) or in a single epoch, after initial convergence of the tropospheric delay (with three frequency signals), even up to hundreds of kilometers away from the nearest reference station While previous WARTK research has been devoted to implementing the concept and assessing its feasibility, considering in particular the accuracy achievable, the work reported in this paper focused on consolidating the results by analyzing a large and representative data set, and on deeper analysis of the integrity issue It was carried out in the context of the Multi-constellation Regional System (MRS) project, within the European Space Agency GNSS Evolution Programme, with the aim of designing a high accuracy service for GPS and/or Galileo Three months of actual data, from more than 25 permanent GPS stations in Europe, have been processed (some of them as a roving user), for high-, mid- and low-solar cycle conditions (in 2002, 2004 and 2006 respectively) In addition, several ionospheric storms occurred during the selected periods, with Dst values reaching up to � 150 nT Results based on these data show that user domain integrity was maintained for baselines of up to 400 km At the 95th percentile, the daily horizontal and vertical position errors were 20 and 30 cm, respectively, and the corresponding protection levels were about 1 and 2 m The convergence time was around 5 minutes with actual GPS constellation data The benefits of using a multi-constellation system were also studied, with simulated GPS and three-frequency Galileo data, showing that it is possible to reduce the convergence time to a few seconds

Journal ArticleDOI
13 May 2012
TL;DR: The challenges that must be addressed by satellite navigation for aircraft guidance are reviewed and the upcoming changes to satellite navigation are described, which include the launch of new constellations and the introduction of new civil signals.
Abstract: Satellite navigation has been used for aircraft navigation for more than 50 years. In the last ten years, the capabilities of satellite navigation have been expanded to more demanding phases of flight, in particular vertical guidance down to 200 ft, thanks to the implementation of augmentation systems. In this paper, we attempt to predict the state of satellite navigation in the next 15 years. We will start by reviewing the challenges that must be addressed by satellite navigation for aircraft guidance. Then, we will describe the current techniques that enable satellite navigation for aviation and the level of performance they achieve today. This will be followed by a description of the upcoming changes to satellite navigation, which include the launch of new constellations and the introduction of new civil signals. Despite these developments, satellite navigation is inherently vulnerable to radio-frequency interference so that backup navigation systems are still necessary. Nonetheless, these improvements will have a great impact on the availability and level of service achieved by satellite navigation, in particular enabling worldwide coverage of vertical guidance.

Patent
19 Mar 2012
TL;DR: In this article, methods and apparatus for processing of GNSS signals are presented, including GNSS processing with predicted precise clocks, GNSS data processing with mixed-quality data, and delta phase correction for incorrect starting position.
Abstract: Methods and apparatus for processing of GNSS signals are presented. These include GNSS processing with predicted precise clocks, GNSS processing with mixed-quality data, GNSS processing with time-sequence maintenance, GNSS processing with reduction of position jumps in low-latency solutions, GNSS processing with position blending to bridge reference station changes, and GNSS processing with delta-phase correction for incorrect starting position.

Patent
15 Feb 2012
TL;DR: In this paper, a navigation module and method for providing an INS/GNSS navigation solution for a device that can either be tethered or move freely within a moving platform is provided, comprising a receiver for receiving absolute navigational information from an external source (e.g., such as a satellite), an assembly of self- contained sensors capable of obtaining readings about the device, and further comprising at least one processor, coupled to receive the output information from the receiver and sensor assembly, and operative to produce an enhanced navigation solution.
Abstract: A navigation module and method for providing an INS/GNSS navigation solution for a device that can either be tethered or move freely within a moving platform is provided, comprising a receiver for receiving absolute navigational information from an external source (e.g., such as a satellite), an assembly of self- contained sensors capable of obtaining readings (e.g.. such as relative or non- reference based navigational information) about the device, and further comprising at least one processor, coupled to receive the output information from the receiver and sensor assembly, and operative to integrate the output information to produce an enhanced navigation solution. The at least one processor may operate to provide a navigation solution by benefiting from nonlinear models and filters that do not suffer from approximation or linearization and which enhance the navigation solution of the device.

01 Feb 2012
TL;DR: This paper examines a relatively new and growing source of RFI: Personal Privacy Devices (PPDs) that aim to prevent people and vehicles from being tracked by GNSS within a limited area, and suggests a means of classifying RFI affecting GNSS into three categories.
Abstract: RF interference (RFI) has been and will continue to be a significant worry for GNSS users. This paper introduces several different types of RFI, categorizes them based upon the intent (if any) of the RFI transmitter, and then examines a relatively new and growing source of RFI: Personal Privacy Devices (PPDs) that aim to prevent people and vehicles from being tracked by GNSS within a limited area. Unfortunately, signals from PPDs are not well-controlled and can interfere with GNSS receivers several hundred meters away. The impact of PPDs on the GBAS reference station site at Newark Airport, New Jersey and the WAAS reference station at Leesburg, Virginia are illustrated. While GBAS ground station monitoring prevents PPDs from posing a significant integrity threat, PPDs can force the sudden loss of service and thus harm continuity and availability. The hardware and software modifications made to the Newark GBAS installation to reduce this impact are described, and the future benefits of more-flexible ground-station siting and GNSS modernization are also identified. 1.0 Introduction and RF Interference Categorization Because Global Navigation Satellite System (GNSS) signals are very weak when received by user equipment, they are vulnerable to radio frequency interference (RFI). Signals that overlap with GNSS frequencies are likely to come from transmitters much closer than the GNSS satellites. Therefore, these signals can easily "overpower" the GNSS signals and make them unusable. To protect GNSS, existing ITU and FCC regulations prohibit the intentional broadcast of any non-GNSS signals on or near GPS L1/Galileo E1, while lesser protections apply to the GPS L2 and GPS L5/Galileo E5A frequencies. Despite these protections, RFI affecting GNSS is occasionally observed, and its apparent frequency has increased significantly with the number of civil GNSS users. In order to better understand the many possible sources of RFI and their potential effects on GNSS, this paper suggests a means of classifying RFI affecting GNSS into three categories. These categories are not all-inclusive, nor do their names fit all possibilities, but they help to separate RFI scenarios in a way that makes it easier to forecast impacts and design mitigations. The first category is malicious interference, meaning RFI that is intentionally transmitted to prevent the use of GNSS (or make its use hazardous) for as many users as possible. Coordinated hostile broadcast of RFI, while hopefully very rare, has the potential to make GNSS unusable over large regions and is difficult to defeat. Therefore, it makes sense to provide non-GNSS backup services to support transportation and other critical infrastructure needs [1]. The second category, and the focus of this paper, is uninformed interference, which results from the intentional transmission of signals at or near GNSS frequencies but without the desire to cause harm. At first, it may seem that signals deliberately broadcast on or near GNSS frequencies are likely aimed at harming GNSS users, but this is not true of the vast majority of cases, as will be illustrated in the following sections. Personal Privacy Devices, or PPDs, fall into this category and are of particular concern because they have become numerous in the last few years. The third category is accidental interference, which results from unintentional transmissions at or near GNSS frequencies. This usually is due to malfunctions of equipment that is designed to transmit at other frequencies or not to transmit at all. It is less common than uninformed interference both because malfunctions are rare and because they are more rapidly detected now that many GNSS receivers are likely to be in use nearby. On the other hand, accidental interference is more variable because it is not designed to prevent harm to users. Section 2.0 of this paper provides past and recent examples of accidental and uninformed RFI. Section 3.0 focuses on PPD interference and illustrates the Figure 1: RF Interferer Location on Stanford Campus Figure 2: Area at Stanford where GPS was Unusable characteristics of PPDs. Section 4.0 shows the impact of PPDs on the Wide Area Augmentation System (WAAS) Reference Station (WRS) in Leesburg, Virginia, while Section 5.0 describes their more-severe impact on the Ground Based Augmentation System (GBAS) ground facility at Newark Airport in New Jersey. Section 6.0 describes the GBAS hardware and software modifications being pursued to limit the impact of PPDs at Newark Airport so that acceptable GBAS Category I precision approach service can be provided. Section 7.0 concludes the paper and looks forward to the additional mitigation steps that will be made possible by GNSS modernization. 2.0 Examples of RF Interference to GPS Figures 1 and 2 show an instance of RF interference to GPS that occurred at Stanford University in 1999. At the time, construction was occurring in the Engineering section of the Stanford campus. A camera had been Figure 3: RF Interference at Moss Landing Harbor [2] installed on the Durand Building with a good view of the construction site, and an attached datalink transmitted digital pictures of the site to the construction headquarters trailer to allow progress to be monitored. This proceeded without incident until, for some reason, the datalink transitioned from its primary frequency of 1530 MHz to its secondary one of 1570 MHz, which is very close to the GPS L1 frequency of 1575.45 MHz. The GPS lab at Stanford discovered that GPS was suddenly "gone"  we could not acquire or track any signals. We also discovered that other GPS users in the area were affected, including the helicopters that transported severe cases to Stanford Hospital. This made it clear that the outage zone had a radius of at least 1 km. The cause was not immediately evident, but the use of directional antennas and signal analyzers allowed us to track down the offending device and (manually) remove its power source, after which GPS became usable again. Once the offending data transmitter was discovered, Todd Walter of Stanford communicated with the device's designers, who knew that their secondary transmission frequency was close to GPS L1 but thought that such transmissions were legal as long as they remained below a certain power level. In other words, they had no intention of interfering with GPS and had no idea that they were capable of doing so. In any case, this company's understanding was incorrect no intentional transmissions (regardless of power level) are allowed this close to L1. At this time, the civil use of GPS was relatively new, and it is not surprising that the regulations protecting it were not well understood. Uninformed interference due to misunderstandings of this sort should be less likely now that GNSS is well-established. Figure 3 shows another, well-known RFI incident from 2001 that was previously described in [2]. This was an example of accidental interference caused by amplifiers attached to UHF/VHF antennas for receiving over-the-air Figure 4: RFI Generated by GPS Repeater at German

Proceedings ArticleDOI
21 May 2012
TL;DR: The characteristics of each of theGNSS signals are described, and the performance benefits that will be provided to the precise time and frequency community as the GNSS evolves are highlighted.
Abstract: This paper provides an overview of Global Navigation Satellite System (GNSS) signals. Today, GNSS comprises two major constellations: (1) the United States' Global Positioning System (GPS), and (2) the Russian Federation's Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS). Two other major constellations are being deployed. Additionally, regional systems have been deployed or are planned. Whereas most GNSS timing receivers today rely only upon the legacy GPS signals, it is anticipated in the near future that multi-system receivers will become the norm. This paper describes the characteristics of each of the GNSS signals, and highlights the performance benefits that will be provided to the precise time and frequency community as the GNSS evolves.

Proceedings ArticleDOI
23 Apr 2012
TL;DR: The GPStation-6 as mentioned in this paper is the next generation GNSS ionospheric scintillation and TEC monitor, incorporating the proven GSV4004B receiver design with the ability to track multi-constellation, multi-frequency, GNSS measurements.
Abstract: The ionosphere, if not modeled sufficiently well, is the largest contributor of error in single frequency GNSS receivers. Modeling ionospheric effects is a major concern for a number of GNSS applications. Ionospheric disturbances induce rapid fluctuations in the phase and the amplitude of received GNSS signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. GNSS signals, although vulnerable, themselves provide an excellent way to measure the ionospheric effect continuously worldwide. Until now, ionospheric monitoring was performed using receivers such as the GSV4004B receiver, which was largely based on GPS only dual frequency receivers. Semi-codeless tracking of the GPS L2 signal greatly limited the accuracy, robustness and utility of the ionospheric TEC measurements and was useless for scintillation measurements on L2. The GPS modernization program, the restored GLONASS, and the upcoming GNSS constellations (Galileo and Compass) bring forth huge benefits for ionospheric monitoring. This paper introduces the NovAtel's next generation GNSS ionospheric scintillation and TEC monitor, the GPStation-6. By incorporating the proven GSV4004B receiver design with the ability to track multi-constellation, multi-frequency, GNSS measurements, the new receiver engine provides robust and less noisy ionospheric measurements.

Journal ArticleDOI
TL;DR: This analysis assesses the self-interference within GNSS, and establishes their multiple access capacity, by examining the code interactions between satellites, and considers cross-correlation properties of the codes at all possible Doppler frequency offsets between satellites.
Abstract: Global Navigation Satellite Systems (GNSS) are growing from the current US GPS and Russian GLONASS to additional European Galileo and Chinese Compass systems. Along with the growth of the systems, the number of satellites will also increase. The whole family of GNSS is projected to consist of about 120 satellites by 2030. Moreover, the new satellites are capable of transmitting multiple signals in multiple frequency bands. Altogether there will be more than 300 GNSS signals broadcast in the future. The growing number of GNSS satellites and signals enable greater redundancy for positioning. On the other hand, the signals interfere with each other due to overlapping frequency bands. Here we answer the question: how many satellites are too many? We assess the self-interference within GNSS, and hence establish their multiple access capacity, by examining the code interactions between satellites. This analysis considers cross-correlation properties of the codes at all possible Doppler frequency offsets between satellites. We first approach the question theoretically by calculating auto- and cross-correlation properties of random sequences with binary phase shift keying (BPSK) modulation and binary offset carrier (BOC) modulation. With the theoretical result of pure random sequences as a guideline, we then use real broadcast pseudorandom noise (PRN) codes of the current Galileo GIOVE and Compass-M1 satellites to further analyze various correlation properties over a range of Doppler frequency offset. We ultimately establish the multiple access capacity of GNSS.

Book
29 Mar 2012
TL;DR: In this article, the authors present a hands-on guide to GNSS, with emphasis on GPS and GLONASS, and explore numerous practical examples and case studies and get handson user experience with a bundled real-time software receiver, signal simulator and a set of signal data, enabling users to create their own GNSS lab for research or study.
Abstract: Bridge the gap between theoretical education and practical work experience with this hands-on guide to GNSS, which features:A clear, practical presentation of GNSS theory, with emphasis on GPS and GLONASSAll the essential theory behind software receivers and signal simulators Key applications in navigation and geophysics, including INS aiding, scintillation monitoring, earthquake studies and morePhysical explanations of various important phenomena, including the similarity of code delay and phase advance of GNSS signals, and negative cross-correlation between scintillation intensity and phase variations.Whether you are a practising engineer, a researcher or a student, you will gain a wealth of insights from the authors' twenty-five years of experience. You can explore numerous practical examples and case studies and get hands-on user experience with a bundled real-time software receiver, signal simulator and a set of signal data, enabling you to create your own GNSS lab for research or study.

01 Jan 2012
TL;DR: Modelling and simulation activities focussed on the AEROSONDE UAV platform and considered the possible augmentation provided by interferometric GNSS techniques to a low-cost and low-weight/volume integrated navigation system recently developed at Cranfield University.
Abstract: This paper presents the results of a research activity performed by Cranfield University to assess the potential of carrierphase Global Navigation Satellite Systems (GNSS) for attitude determination and control of small to medium size Unmanned Aerial Vehicles (UAV). Both deterministic and recursive (optimal estimation) algorithms are developed for combining multiple attitude measurements obtained from different observation points (i.e., antenna locations), and their efficiencies are tested in various dynamic conditions. The proposed algorithms converge rapidly and produce the required output even during high dynamics manoeuvres. Results of theoretical performance analysis and simulation activities are presented in this paper, with emphasis on the advantages of the GNSS interferometric approach in UAV applications (i.e., low cost, high data-rate, low volume/weight, low signal processing requirements, etc.). Modelling and simulation activities focussed on the AEROSONDE UAV platform and considered the possible augmentation provided by interferometric GNSS techniques to a low-cost and low-weight/volume integrated navigation system recently developed at Cranfield University, which employs a Vision-based Navigation (VBN) system, a Micro-Electro-mechanical Sensor (MEMS) based Inertial Measurement Unit (IMU) and code-range GNSS (i.e., GPS and GALILEO) for position and velocity computations. The integrated VBN-IMU-GNSS (VIG) system is augmented by using the inteferometric GNSS Attitude Determination (GAD) and a comparison of the performance achievable with the VIG and VIG/GAD integrated Navigation and Guidance Systems (NGS) is presented. Finally, the data provided by these NGS are used to optimise the design of an hybrid controller employing Fuzzy Logic and Proportional-Integral-Derivative (PID) techniques for the AEROSONDE UAV.

Dissertation
03 Jul 2012
TL;DR: The concept of integrity in civil aviation is presented in order to understand the objectives and constraints of existing GNSS integrity monitoring systems, and a nominal pseudorange measurement model suitable for integrity-driven applications in urban environments is calculated.
Abstract: Global Navigation Satellite Systems (GNSS) integrity is defined as a measure of the trust that can be placed in the correctness of the information supplied by the navigation system Although the concept of GNSS integrity has been originally developed in the civil aviation framework as part of the International Civil Aviation Organization (ICAO) requirements for using GNSS in the Communications, Navigation, and Surveillance / Air Traffic Management (CNS/ATM) system, a wide range of non-aviation applications need reliable GNSS navigation with integrity, many of them in urban environments GNSS integrity monitoring is a key component in Safety of Life (SoL) applications such as aviation, and in the so-called liability critical applications like GNSS-based electronic toll collection, in which positioning errors may have negative legal or economic consequences At present, GPS integrity monitoring relies on different augmentation systems (GBAS, SBAS, ABAS) that have been conceived to meet the ICAO requirements in civil aviation operations For this reason, the use of integrity monitoring techniques and systems inherited from civil aviation in non-aviation applications needs to be analyzed, especially in urban environments, which are frequently more challenging than typical aviation environments Each application has its own requirements and constraints, so the most suitable integrity monitoring technique varies from one application to another This work focuses on Electronic Toll Collection (ETC) systems based on GNSS in urban environments Satellite navigation is one of the technologies the directive 2004/52/EC recommends for the European Electronic Toll Service (EETS), and it is already being adopted: toll systems for freight transport that use GPS as primary technology are operational in Germany and Slovakia, and France envisages to establish a similar system from 2013 This dissertation begins presenting first the concept of integrity in civil aviation in order to understand the objectives and constraints of existing GNSS integrity monitoring systems A thorough analysis of GNSS-based ETC systems and of GNSS navigation in urban environments is done afterwards with the aim of identifying the most suitable road toll schemes, GNSS receiver configurations and integrity monitoring mechanisms Receiver autonomous integrity monitoring (RAIM) is chosen among other integrity monitoring systems due to its design flexibility and adaptability to urban environments A nominal pseudorange measurement model suitable for integrity-driven applications in urban environments has been calculated dividing the total pseudorange error into five independent error sources which can be modelled independently: broadcasted satellite clock corrections and ephemeris errors, ionospheric delay, tropospheric delay, receiver thermal noise (plus interferences) and multipath In this work the fault model that includes all non-nominal errors consists only of major service failures Afterwards, the GNSS integrity requirements are derived from the relationship between positioning failures and toll charging errors Two RAIM algorithms are studied The first of them is the Weighted Least Squares Residual (WLSR) RAIM, widely used in civil aviation and usually set as the reference against which other RAIM techniques are compared One of the main challenges of RAIM algorithms in urban environments is the high unavailability rate because of the bad user/satellite geometry For this reason a new RAIM based on the WLSR is proposed, with the objective of providing a trade-off between the false alarm probability and the RAIM availability in order to maximize the probability that the RAIM declares valid a fault-free position Finally, simulations have been carried out to study the performance of the different RAIM and ETC systems in rural and urban environments In all cases, the availability obtained with the novel RAIM improve those of the standard WLSR RAIM

01 Jan 2012
TL;DR: In this article, the authors consider a cooperative positioning approach, where receivers exchange data and information with their neighbors in unstructured P2P networks, without a control or fusion center.
Abstract: To improve the performance of GNSS receivers in hostile environments, we consider a Cooperative Positioning approach, where receivers exchange data and information with their neighbors. We focus on unstructured P2P networks, without a control or fusion center. We show that a significant reduction of the acquisition time can indeed by achieved when GNSS aiding quantities like Doppler, satellite Carrierto-Noise ratio and secondary code delay are provided by some aiding peers. The approach is clearly similar to that of Assisted GNSS, but does not require a fixed infrastructure and may better take into account the local environment. Since, in the near future, multi-standard devices will be more and more inter-connected, GNSS Cooperative Positioning may soon become an alternative or a complement to fixed augmentation systems

Proceedings ArticleDOI
01 Oct 2012
TL;DR: In this work GPS/GLONASS systems are combined and the benefits of the aforesaid aids are assessed, with main focus being the improvements in terms of integrity; single point GNSS and snapshot RAIM algorithms are herein considered.
Abstract: Urban canyon is a critical scenario for satellite navigation, because many GNSS signals are blocked by artificial obstacles or severely degraded; in standalone mode GPS, currently the main GNSS, cannot guarantee an accurate and continuous positioning. A possible approach to overcome these limitations is the use of multiple GNSS systems. GLONASS, the Russian navigation satellite system, is currently fully operational and is the main candidate to support this thesis. Urban scenario is mainly affected by multipath phenomenon, yielding several blunders into the measurements and unacceptable errors in the navigation solution. The integrity concept was introduced for safety-of-life application as aviation to provide timely warnings to users when a system should not be used for navigation, and then it was expanded to not safety-of-life service as urban navigation. RAIM (Receiver Autonomous Integrity Monitoring) techniques are user-level integrity methods based on consistency check of redundant measurements. This check is crucial because only at user-level certain local errors, such as multipath and local interferences, can be detected. Multi-constellation GNSS improves navigation solution in terms of accuracy and continuity; a further enhancement is achievable even in terms of integrity owing to the gained redundancy. The multi-constellation use implies a further unknown related to the intersystem time scale offset, requiring the “sacrifice” of one measurement. This parameter is observed to be quasi-constant in the short term, so an aiding can be introduced to account for its behavior. A similar approach can be adopted for altitude considering its slow variations in urban scenario. In this work GPS/GLONASS systems are combined and the benefits of the aforesaid aids are assessed, with main focus being the improvements in terms of integrity; single point GNSS and snapshot RAIM algorithms are herein considered. PVT and RAIM algorithms are developed in MatLab® environment and belong to a tool implemented by PANG (PArthenope Navigation Group).

Proceedings Article
09 Jul 2012
TL;DR: A version of the extended Kalman filter augmented by a 3D model, referred to as 3D AEKF, for GNSS navigation in NLOS context is proposed, which uses constructively non-line-of-sight (NLOS) signals.
Abstract: In this paper, we introduce a GNSS positioning approach that uses constructively non-line-of-sight (NLOS) signals. A 3D model of the environment is used to predict the geometric paths of NLOS signals. More precisely, we propose a version of the extended Kalman filter augmented by a 3D model, referred to as 3D AEKF, for GNSS navigation in NLOS context. In the proposed approach, the measurement model traditionally based on the trilateration equations is constructed from the received paths estimated by the 3D model. The Jacobian of the measurement model is calculated through knowledge of the wall on which the reflection has occured. To use even less reliable measurements, a robust version of the 3D AEKF is also proposed. Simulations conducted in different realistic configurations allow the performance of the proposed method to be evaluated.

Proceedings ArticleDOI
01 Dec 2012
TL;DR: The reliability of integer ambiguity estimation depends on the strength of the underlying GNSS model and on the applied integer estimation method as discussed by the authors, which brings certain challenges and limitations that need to be addressed and have not all been solved so far.
Abstract: Next generation Global Navigation Satellite Systems will open the door to a whole new field of applications, for example in Earth observation, construction, and safety-of-life navigation. This implies very high requirements not only on precision and availability, but also on reliability. Integer carrier phase ambiguity resolution is the key to (near) real-time and high-precision GNSS positioning and navigation. The reliability of integer ambiguity estimation depends on the strength of the underlying GNSS model and on the applied integer estimation method. This brings certain challenges and limitations that need to be addressed and have not all been solved so far. The aim of this contribution is to address these remaining challenges and limitations: it will be explained why it is important to do so, and how solutions can be obtained. Experimental results will be used to underpin the importance and potential improvement in terms of precision and/or reliability.

Patent
Jason Rife1
29 Jun 2012
TL;DR: In this article, the authors present a fault detection system for verifying the quality of global navigation satellite system (GNSS) measurements, which includes a GNSS receiver, a wireless communications device, and a fault detector.
Abstract: Systems and methods are disclosed herein for verifying the quality of global navigation satellite system (GNSS) measurements. The system includes a GNSS receiver, a wireless communications device, and a fault detection processor. The GNSS receiver includes a GNSS antenna for receiving signals from a plurality of global navigation satellites and a processor for calculating a ranging measurement for each of the global navigation satellites from the GNSS receiver to the global navigation satellite. The wireless communications device receives ranging measurements from at least one other GNSS receiver. The fault detection processor performs a fault detection algorithm to determine if there is an anomaly affecting the ranging measurements of the GNSS receiver and the at least one other GNSS receiver.

Journal ArticleDOI
TL;DR: Despite the purported simplicity of the ratio detection method, it is shown that its complexity is comparable to or even higher than the one of threshold comparison with adaptive threshold setting.
Abstract: A comparison between two widespread global navigation satellite system (GNSS) acquisition strategies is presented. The first strategy bases its decision on comparing the energy within a cell to a threshold, while the second one uses the ratio between the two largest cell energies. It is shown that the first method outperforms the second one in terms of receiver operating characteristics (ROCs) in many practically relevant cases. Moreover, despite the purported simplicity of the ratio detection method, it is further shown that its complexity is comparable to or even higher than the one of threshold comparison with adaptive threshold setting.

Journal ArticleDOI
TL;DR: In this article, a methodology for reliable surveying and processing of GNSS observations in a rapid static survey conducted in open terrain as well as with the limited availability of satellites is presented.
Abstract: This paper presents a methodology for reliable surveying and processing of GNSS observations in a rapid static survey conducted in open terrain as well as with the limited availability of satellites. The surveying and data processing technology presented allows reliable determination of coordinates under difficult observation conditions, e.g. in a forest with significant obstacles to satellite signal reception. The test GNSS surveys were conducted in two points with full availability of satellites and a point with a high intensity of obstructions. The test point coordinates were determined by three GNSS receivers positioned simultaneously in line on a special base at a distance of 0·5 m from one another. Given the possible gross errors of the determined baseline coordinates, the simultaneous application of three GPS/GLONASS receivers for a single point allows reliable determination of coordinates even in locations with severe obstructions. Test surveys were conducted using Topcon Hyper Pro receive...

Proceedings ArticleDOI
01 Nov 2012
TL;DR: A ubiquitous outdoor/indoor GNSS navigation platform that utilizes GPS (Global Positioning System), GLONASS, and pulsed pseudolite (PL) signals for seamless positioning is presented.
Abstract: Pseudolites provide a means for bridging the gap between outdoors and indoors when GNSS (Global Navigation Satellite System) positioning is concerned. This paper presents a ubiquitous outdoor/indoor GNSS navigation platform that utilizes GPS (Global Positioning System), GLONASS, and pulsed pseudolite (PL) signals for seamless positioning. When a pseudolite signal is pulsed to efficiently transmit the GNSS-like signal only at particular time instants, interference problems between the terrestrial pseudo-satellite signals and the space-based satellite signals are significantly reduced. Pulsed pseudolites are strategically placed indoors at known locations at the ends of building corridors to assist high-sensitivity GPS and GLONASS positioning. A particle filtering solution is implemented to combine the high-sensitivity GNSS and the pseudolite proximity information in order to provide a seamless outdoor/indoor positioning platform. As demonstrated with real-life experiments, pseudolites provide a convenient navigation aid indoors for a GNSS receiver without the need for using additional hardware.

Patent
02 Aug 2012
TL;DR: In this article, a system and method for monitoring integrity of a Global Navigation Satellite System (GNSS) is presented, based on a comparison of the GNSS location with one or more locations received from at least one other GNSS.
Abstract: A system and method for monitoring integrity of a Global Navigation Satellite System (GNSS) are provided. Integrity of a GNSS location is assessed based on a comparison of the GNSS location with one or more locations received from at least one other GNSS. Integrity of the GNSS location is also assessed based on a comparison of the GNSS location with one or more locations obtained from signals generated by one or more known located emitters. Integrity of the GNSS location is also assessed based on a comparison of the GNSS location with historical data, which may include contextual information of recent GNSS locations of a user equipment, measurements made by an inertial navigation system of the user equipment, and prior measurements made by the user equipment during similar paths. An integrity warning is outputted when one or more of the integrity assessments indicate a loss of integrity of GNSS.