Showing papers on "GNSS augmentation published in 2010"

Lane-Level Integrity Provision for Navigation and Map Matching With GNSS, Dead Reckoning, and Enhanced Maps

Abstract: Lane-level positioning and map matching are some of the biggest challenges for navigation systems. Additionally, in safety applications or in those with critical performance requirements (such as satellite-based electronic fee collection), integrity becomes a key word for the navigation community. In this scenario, it is clear that a navigation system that can operate at the lane level while providing integrity parameters that are capable of monitoring the quality of the solution can bring important benefits to these applications. This paper presents a pioneering novel solution to the problem of combined positioning and map matching with integrity provision at the lane level. The system under consideration hybridizes measurements from a global navigation satellite system (GNSS) receiver, an odometer, and a gyroscope, along with the road information stored in enhanced digital maps, by means of a multiple-hypothesis particle-filter-based algorithm. A set of experiments in real environments in France and Germany shows the very good results obtained in terms of positioning, map matching, and integrity consistency, proving the feasibility of our proposal.

Extended Receiver Autonomous Integrity Monitoring (eRAIM) for GNSS/INS Integration

Abstract: The integration of globe navigation satellite system (GNSS) with inertial navigation system (INS) is being heavily investigated as it can deliver more robust and reliable systems than either of the individual systems. In order to ensure the integrity of navigation solutions, it is necessary to incorporate an effective quality control scheme which uses redundant information provided by both the measurement and dynamic models. As the GNSS receiver autonomous integrity monitoring (RAIM) algorithms are well developed, here they are adapted to integrated GNSS/INS systems referred as extended RAIM ( eRAIM ) , which are derived from the least-squares estimators of the state parameters in a Kalman filter, to assess GNSS/INS performance for a tightly coupled scenario. In addition to the RAIM capabilities, eRAIM procedures are able to detect faults in the dynamic model and isolate them from the measurement model. The analysis includes outlier detection and identification capabilities, reliability and separability m...

Navigation Signal Processing for GNSS Software Receivers

Abstract: The navigation signal processing theory is described within this text for generic navigation signals to allow a broad range of applications, beyond that of Global Navigation Satellite System (GNSS). Chapter 1 introduces requirements for navigation signals and are illustrated with one Global Positioning System (GPS), one Galileo, and two pulsed signals. Chapter 2 covers software-defined radio technology, together with the architecture and the data flow of a permanent GNSS reference station in Chapter 3. Theoretical signal-processing aspects are the focus of Chapters 4 and 5, and the focus is shifted to implementation in Chapters 6 through 9. Chapter 10 presents an innovative high-precision software radio concept using double-difference correlators, in addition to double-difference pseudorange and carrier-phase observations to increase carrier-phase tracking stability for real-time kinematic applications. Some MATLAB (a high-level technical computing language) and assembler programs that illustrate the core signal-processing concepts of a navigation receiver may be found for this book at the Artech House website, www.artechhouse.com, and this software is described in Chapter 11. This book should help in building advanced navigation software receivers, although it is not for beginners.

Gnss integrated multi-sensor control system and method

Abstract: A GNSS integrated multi-sensor guidance system for a vehicle assembly includes a suite of sensor units, including a global navigation satellite system (GNSS) sensor unit comprising a receiver and an antenna. An inertial measurement unit (IMU) outputs vehicle dynamic information for combining with the output of the GNSS unit. A controller with a processor receives the outputs of the sensor suite and computes steering solutions, which are utilized by vehicle actuators, including an automatic steering control unit connected to the vehicle steering for guiding the vehicle. The processor is programmed to define multiple behavior-based automatons comprising self-operating entities in the guidance system, which perform respective behaviors using data output from one or more sensor units for achieving the behaviors. A GNSS integrated multi-sensor vehicle guidance method is also disclosed.

Practical method for upgrading existing GNSS user equipment with tightly integrated Nav-Com capability

Abstract: A method for adding an integrated Nav-Com capability to any Global Navigation Satellite System (GNSS) user equipment, such as GPS receivers, requires no hardware modifications to the existing user equipment. The concept may be applied to a Defense Advanced GPS Receiver (DAGR) and combines Low Earth Orbiting (LEO) satellites, such as Iridium, with GPS or other GNSS systems to significantly improve the accuracy, integrity, and availability of Position, Navigation, and Timing (PNT), and to enable new communication enhancements made available by the synthesis of precisely coupled navigation and communication modes; to achieve time synchronization stability to the required sub-20 ps level between the existing DAGR and a plug-in iGPS enhancement module, a special -purpose wideband reference signal is generated by the iGPS module and coupled to the DAGR via the existing antenna port, so that no hardware modification of the DAGR is required.

GNSS-based tracking of fixed or slow-moving structures

Abstract: A multi-antenna GNSS system and method provide earth-referenced GNSS heading and position solutions. The system and method compensate for partial blocking of the antennas by using a known attitude or orientation of the structure, which can be determined by an orientation device or with GNSS measurements. Multiple receiver units can optionally be provided and can share a common clock signal for processing multiple GNSS signals in unison. The system can optionally be installed on fixed or slow-moving structures, such as dams and marine vessels, and on mobile structures such as terrestrial vehicles and aircraft.

GNSS for Vehicle Control

Abstract: The use of Global Navigation Satellite Systems (GNSS) to automatically control ground vehicles has drawn increasing interest as GNSS such as Global Positioning Systems (GPS) have grown more pervasive. This resource offers a thorough understanding of this emerging application area of GNSS and covers a wide range of key topics, including ground vehicles models, psuedolites, highway vehicle control, unmanned ground vehicles, farm tractors, and construction equipment. The use of algorithms to detect a vehicle's position relative to road features is described, as well as methods for estimating parameters to be used in a mathematical model.

Assimilating GNSS Signals to Improve Accuracy, Robustness, and Resistance to Signal Interference

Abstract: A method for upgrading GNSS equipment to improve position, velocity and time (PVT) accuracy, increase PVT robustness in weak-signal or jammed environments and protect against counterfeit GNSS signals (spoofing). A GNSS Assimilator couples to an RF input of existing GNSS equipment, e.g., a GPS receiver, and extracts navigation and timing information from available RF signals, including non-GNSS signals, or direct baseband aiding, e.g., from an inertial navigation system, frequency reference, or GNSS user. The Assimilator fuses the diverse navigation and timing information to embed a PVT solution in synthesized GNSS signals provided to a GNSS receiver RF input. The code and carrier phases of the synthesized GNSS signals are aligned with those of actual GNSS signals to appear the same at the target receiver input. The Assimilator protects against spoofing by continuously scanning incoming GNSS signals for signs of spoofing, and mitigating spoofing effects in the synthesized GNSS signals.

Anti-spoofing and open GNSS signal authentication with signal authentication sequences

Abstract: Global Navigation Satellite System (GNSS) signal authentication is a requirement for a number of applications GNSS authentication has been proposed with aiding techniques that can be applied to the existing GPS and as a new security function for future GNSS The paper proposes a concept of a new authentication scheme based on signal authentication sequences that can be integrated in GNSS The method works on systems that provide an open and encrypted service on the same frequency The scheme would require minimum impact to the system The architecture is explained in the different components of ground, space and user segment A simulation of the architecture has been implemented in Matlab and performances and test results are shown The paper concludes with suggestions of optimal parameters for an hypothetical implementation, explaining the future research steps

Hybrid Data Fusion and Tracking for Positioning with GNSS and 3GPP-LTE

Abstract: Global navigation satellite systems (GNSSs) can provide reliable positioning information under optimum conditions, where at least four satellites can be accessed with sufficient quality. In critical situations, for example, urban canyons or indoor, due to blocking of satellites by buildings and severe multipath effects, the GNSS performance can be decreased substantially. To overcome this limitation, we propose to exploit additionally information from communications systems for positioning purposes, for example, by using time difference of arrival (TDOA) information. To optimize the performance, hybrid data fusion and tracking algorithms can combine both types of sources and further exploit the mobility of the user. Simulation results for different filter types show the ability of this approach to compensate the lack of satellites by additional TDOA measurements from a future 3GPP-LTE communications system. This paper analyzes the performance in a fairly realistic manner by taking into account ray-tracing simulations to generate a coherent environment for GNSS and 3GPP-LTE.

Gnss optimized aircraft control system and method

Abstract: A GNSS system in combination with a hydraulically-actuated, airborne dispenser for a dry material crop dusting system to optimize the distribution of dry materials over a particular tract of land. A GNSS subsystem is included using at least one GNSS antenna and one GNSS receiver located on the aircraft. The aircraft is equipped with an electronic/hydraulic crop dusting subsystem connected to a GNSS CPU. The GNSS ranging signals received by the antennas are processed by a receiver and processor system for determining the vehicle's position and dynamic attitude in three dimensions (3D). A graphical user interface (GUI) placed in the vehicle will give the driver a real-time view of his or her current bearing as well as a calculated “optimal path” based on calculations and variable data, such as wind speed and direction, material moisture content, altitude, air speed and other conditions. The system is adapted for operation in a differential GNSS (DGNSS) mode utilizing a base station at a fixed location.

Removing biases in dual frequency gnss receivers using sbas

Abstract: A method for removing biases in dual frequency GNSS receivers circumvents the need for ionosphere corrections by using L2(P) in combination with either L1(P) or L1(C/A) to form ionosphere-free ranges. A table of biases is stored in microprocessor controller memory and utilized for computing a location using corrected ionosphere-free pseudo ranges, A system for removing biases in dual frequency GNSS receivers includes a dual frequency GNSS receiver and a controller microprocessor adapted to store a table of bias values for correcting pseudo ranges determined using L2(P) in combination with either L1(F) or L1(C/A ).

Development and validation of an OFDM/DVB-T sensor for positioning

Abstract: The use of Global Navigation Satellite System (GNSS) for positioning has grown significantly in recent years thanks in particular to the development of several mass-market applications, such as car navigation or mobile positioning. Unfortunately, in difficult environments such as dense urban or indoor areas, GNSS exhibits degraded performances in terms of precision and availability. The use of signals of opportunity is one of the solutions to replace or assist GNSS in those environments. These signals are communication signals that are usually designed to provide a service in dense environment and can thus be used in location where GNSS is unavailable. Several commercial positioning services based on signals of opportunity already exist such as ROSUM with ATSC digital TV signals, or Skyhook with Wi-Fi signals

Space qualified frequency sources (clocks) for current and future GNSS applications

Abstract: Accurate and stable frequency reference sources are critical for commercial, navigation, military and scientific space applications. Several levels of frequency references are suitable for space applications. This paper discusses similarities and differences among single distributed oscillators for communications satellites, master oscillator groups for communications systems, and atomic clocks for military and navigation systems. This paper builds on reference [1] and broadly describes frequency sources on current and upcoming global navigation satellite systems (GNSS). The three current systems are the Global Navigation Satellite System (GLONASS), the Global Positioning System (GPS), and the Galileo system. The upcoming navigation systems are: China's Compass satellite positioning system, Japan's quasi-zenith satellite system (QZSS), India's regional navigation satellite system (IRNSS), GPS-IIF, and GPS-III.

Intermittent tracking for GNSS

Abstract: A GNSS system operates intermittently and has adaptive activity and sleep time in order to reduce power consumption. The GNSS system provides an enhanced estimate of its position in the absence of GNSS signals of sufficient strength. The user's activity and behavior is modeled and used to improve performance, response time, and power consumption of the GNSS system. The user model is based, in part, on the received GNSS signals, a history of the user's positions, velocity, time, and inputs from other sensors disposed in the GNSS system, as well as data related to the network. During each activity time, the GNSS receiver performs either tracking, or acquisition followed by tracking. The GNSS receiver supports both normal acquisition as well as low-power acquisition.

Nominal GNSS pseudorange measurement model for vehicular urban applications

Abstract: Certain GNSS applications conceived for road users in urban scenarios must meet some particular integrity requirements to assure the system safety, reliability or credibility. For instance, GNSS-based Road User Charging is one of these applications that recently has attracted special interest. A correct design of such applications needs the knowledge of the GNSS error distribution. Furthermore, the GNSS error model should have been built with overbounding techniques. The user is a vehicle equipped with a GNSS receiver that may track different signals of various systems (GPS, Galileo, SBAS), in a single-or dual-frequency configuration. The different error sources contributing to the total pseudorange error are identified, analyzed and modeled, using overbounding techniques when necessary. Finally the pseudorange measurement error model is obtained and analyzed for different receiver configurations.

Antenna and RF front end calibration in a GNSS array receiver

Abstract: The use of spatial-domain signal processing for mitigation of interference signals in receivers of global navigation satellite systems (GNSS) allows for improvement of the overall system performance. To fully benefit from the use of adaptive antenna arrays, the individual signal processing paths in such a multi-antenna system should be thoroughly calibrated. The focus of this paper is on the specifics of such calibration in receivers for satellite navigation systems (e.g. GPS and coming Galileo). The design goals of the antenna and RF front end for GNSS receivers are reviewed. The architecture of a GNSS array receiver for safety-of-life applications with high robustness against radio interference is presented. The practical solutions for the antenna array and RF front-end calibration along with the field test results demonstrating their performance are outlined.

Augmenting GNSS User Equipment to Improve Resistance to Spoofing

Abstract: A method of countering GNSS signal spoofing includes monitoring a plurality of GNSS signals received from a plurality of GNSS signal sources and comparing broadcast data to identify outlying data, which is excluded from generation of a navigation solution defined by the plurality of GNSS signals. The outlying data can be a vestigial signal from a code or carrier Doppler shift frequency. The method includes triggering a spoofing indicator upon identification of the outlying data or other phenomenon. The phenomenon can include a shift in a phase of a measured GNSS navigation data bit sequence or a profile phenomenon of a correlation function resulting from correlation of the incoming GNSS signals with a local signal replica. The profile phenomenon can be the presence of multiple sustained correlation peaks. A nullifying signal can be generated and superimposed over a compromised signal.

System and method for GNSS in-band authenticated position determination

Abstract: The present invention provides a system and method for determining the authenticity of reported positions of GNSS receivers, such as aircraft equipped with GPS positioning devices, and provides an in-band verification capability for GNSS positions by tasking one or more GNSS satellites as designated authentication support (DAS) satellites that transmit corrupted ephemeris data in a pseudo-random error corrupted C/A signal on the L1 band, and the GNSS receivers determine authentication ranges to the DAS satellites and transmit the DAS authentication ranges as part of their position report. The surveillance system can verify the authenticity by comparing the transmitted authentication ranges to true authentication ranges determined using actual ephemeris data and the known C/A code pseudo-random error for the DAS satellites.

ipexSR: A real-time multi-frequency software GNSS receiver

Abstract: Today's Global Navigation Satellite System (GNSS) receivers predominantly utilize hardware based digital signal processing. This approach generally provides high performance and low power consumption GNSS receivers but on the other hand limits the flexibility as the receiver functionality is fixed. The aim of this paper is to present an overview on the ipexSR real-time GNSS software receiver developed at the Institute of Geodesy and Navigation at the University FAF. The receiver does all signal processing in software and therefore is conceptually well suited for many applications which for example may benefit from additional data, utilize different interfaces or have a need for customized integration depth. Starting with an overview of the receiver architecture and signal processing chain some features of the ipexSR are presented. To give an indication of the capabilities of software receiver technology several applications including GNSS signal monitoring and assisted GNSS techniques are presented afterwards. The paper closes with current developments like implementation of a vector tracking loop or the capability to utilize the new Galileo AltBOC signal.

Multi-constellation global navigation satellite system augmentation and assistance

Abstract: A multi-constellation GNSS augmentation and assistance system may include a plurality of reference stations. Each reference station may be adapted to receive navigation data from a plurality of different global navigation satellite systems and to monitor integrity and performance data for each different global navigation satellite system. An operation center may receive the integrity and performance data transmitted from each of the plurality of reference stations. A communication network may transmit a message from the operation center to navcom equipment of a user for augmentation and assistance of the navcom equipment.

Method and system for mobile device based GNSS position computation without ephemeris data

Abstract: A GNSS enabled mobile device receives GNSS assistance data comprising acquisition assistance data, from an A-GNSS server and calculates a relative GNSS position using the receive acquisition assistance data and a local code delay measurement, without using ephemeris data. The received GNSS assistance data comprises an approximate position, acquisition assistance data, satellite almanac data, and/or satellite azimuth and elevation fields, but no ephemeris data. The A-GNSS server calculates corresponding acquisition assistance data at a current time instant and/or one or more future time instants for the approximate position. The satellite azimuth and elevation fields are calculated using local GNSS measurements together with the acquisition assistance data in the received GNSS assistance data are used to calculate the relative GNSS position, which is added to the approximate position to generate an actual GNSS position.

Gnss signal processing to estimate phase-leveled clocks

Abstract: Methods and apparatus are described for processing a set of GNSS signal data derived from code observations and carrier-phase observations at multiple receivers of GNSS signals of multiple satellites over multiple epochs, the GNSS signals having at least two carrier frequencies and a navigation message containing orbit information, comprising: obtaining precise orbit information for each satellite, determining at least one set of ambiguities per receiver, each ambiguity corresponding to one of a receiver-satellite link and a satellite-receiver-satellite link, and using at least the precise orbit information, the ambiguities and the GNSS signal data to estimate a phase-leveled clock per satellite.

DINGPOS: High sensitivity GNSS platform for deep indoor scenarios

Abstract: Deep indoor scenarios are one of the most challenging areas of application for Global Navigation Satellite Systems (GNSS) in personal navigation devices. Especially severe signal attenuation, as well as heavy multipath constrain the use of GNSS in this environment. The project DINGPOS is focusing on the development of a platform for pedestrian users which can acquire and track GNSS signals also under most adverse indoor signal conditions. The main idea of the concept is the extension of the coherent signal integration time of the GNSS receiver to the length of several seconds, which increases the correlation gain significantly. To facilitate this goal, a very long and very precise signal replica is needed. Therefore the system must reproduce the user motion, the navigation message data bits and the satellite constellation precisely. Hence, the system uses a sensor suite of several state of the art indoor positioning sensors and innovative fusion algorithms. The integrating element of the system is a software receiver using Ultra-Tightly Coupling (UTC) implemented by vector tracking. The presented work was performed under the ESA funded contract DINGPOS, ESTEC Ctr. No. 20834.

A Method to Assess Robustness of GPS C/A Code in Presence of CW Interferences

Abstract: Navigation/positioning platforms integrated with wireless communication systems are being used in a rapidly growing number of new applications. The mutual benefits they can obtain from each other are intrinsically related to the interoperability level and to a properly designed coexistence. In this paper a new family of curves, called Interference Error Envelope (IEE), is used to assess the impact of possible interference due to other systems (e.g., communications) transmitting in close bandwidths to Global Navigation Satellite System (GNSS) signals. The focus is on the analysis of the GPS C/A code robustness against Continuous Wave (CW) interference.

Combining the Observations from Different GNSS

Abstract: Until quite recently the precise applications for Global Navigation Satellite Systems (GNSS) were exclusively based on using the American Global Positioning System (GPS). With the much improved stability of the Russian counterpart GLONASS (Global Navigation Satellite System) and the development of alternative systems in Europe (Galileo) or China (Compass) we are facing more and more multi-GNSS applications. The Center for Orbit Determination in Europe (CODE), acting as a global analysis center of the International GNSS Service (IGS), has a long tradition in the combined analysis of data from different GNSS. All CODE contributions to the IGS are in fact generated from a rigorously combined analysis of GPS and GLONASS data — apart from the clock products — for a long time. Inter–system biases are taken into account when generating the procedures to compute multi–GNSS satellite clock corrections. Traditionally, a constant offset between the internal GPS and GLONASS receiver clocks is assumed and set up in the data processing. A detailed analysis revealed on the one hand that this simple approach is not sufficient. It is not necessary, on the other hand, to introduce independent receiver clock parameters for each GNSS. Such an approach would considerably reduce the benefit of the combined processing of observations from different GNSS as opposed to analyzing the measurements of only one GNSS. Finally, a compromise between both strategies seems to be most promising: a piece– wise linear inter–system bias with a resolution of, e.g., one hour.

Vertical Protection Level Equations for Dual Frequency SBAS

Abstract: The L1-only Satellite-Based Augmentation System (SBAS) Minimum Operational Performance Standards (MOPS) were developed long before any SBASs were certified for operation During the development and certification of the Wide Area Augmentation System (WAAS), it was discovered that the zero-mean Gaussian basis of the Vertical Protection Level (VPL) equation was not strictly true for some error sources, and very difficult to sufficiently demonstrate for others The actual data collected in support of system performance demonstrated non-Gaussian behavior Further, sources of small uncorrectable biases were discovered after the original MOPS development These biases can arise from consistent, minor differences in the signal structure from one satellite to another Antenna biases at the satellite, at the reference stations, and at the user are other possible sources of these biases Because the MOPS VPL equation is based upon zero-mean Gaussian error combination, much additional work was required to demonstrate that the actual errors could be sufficiently protected safely Some performance is lost because the system has to implement conservative approaches to account for these discrepancies The advent of dual frequency SBAS affords the opportunity to revisit the MOPS and use different approaches for this new class of user Lessons learned from the L1-only system certification and operation can be leveraged to both ease development of the future dual frequency system and improve user performance This paper examines the VPL equations and proposes changes to directly address these lessons The handling of non- Gaussian behavior and small biases directly address both goals The VPL can be further changed to directly address the threats that most limit availability Without the corrupting influence of the ionosphere, satellite faults become the dominant source of significant error New VPL equations are proposed to specifically account for individual satellite fault modes This paper will demonstrate that by avoiding overly conservative steps required to handle all possible cases, the users will see reduced protection levels and higher availability

Sensor-assisted location-aware mobile device

Abstract: A GNSS enabled mobile device moves from a first area where GNSS signal quality and/or level is above a threshold to a second area where GNSS signal quality and/or level is below the threshold. The GNSS enabled mobile device in the second area determines its own location utilizing previous GNSS measurements in the first area. GNSS signals are received to calculate GNSS measurements whenever the GNSS enabled mobile device is in the first area. The calculated GNSS measurements are utilized to determine a location of the GNSS enabled mobile device within the first area. The GNSS enabled mobile device in the second area utilizes the most current GNSS measurements in the first area to determine its own location. Sensors such as an image sensor, a light sensor, an audio sensor and/or a location sensor are used to refine the location of the GNSS enabled mobile device in the second area.

Opportunistic Frequency Stability Transfer for Extending the Coherence Time of GNSS Receiver Clocks

Abstract: A framework is presented for exploiting the frequency stability of non-GNSS signals to extend the coherence time of inexpensive GNSS receiver clocks. This is accomplished by leveraging stable ambient radio frequency signals, called “signals of opportunity,” to compensate for the frequency instability of the reference oscillators typically used in inexpensive handheld GNSS receivers. Adequate compensation for this frequency instability permits the long coherent integration intervals required to acquire and track GNSS signals with low carrier-to-noise ratios. The goal of this work is to push the use of GNSS deeper indoors or into environments where GNSS may be subject to interference.

A novel evil waveforms threat model for new generation GNSS signals: Theoretical analysis and performance

Abstract: With the advent of new Global Navigation Satellite Systems (GNSS) and signals, Satellite Based Augmentation Systems (SBAS) will rely also on them to provide higher position accuracy. For services based on such systems it is fundamental to protect the user against potential signal distortions in order to ensure the required integrity and performance. SBAS systems usually implement signal deformation monitors which are capable to recognize payload imperfections affecting the received signals in order to discard the corrupted information. The advent of new GNSS signals introduces the necessity to extend already accepted failure models to the new modulations techniques. This paper considers in particular the 2nd-Order Step threat model adopted by the International Civilian Aviation Organization (ICAO) for GPS signals. Starting from the ICAO model, a general threat model affecting the signal generation and transmission hardware is here proposed for Binary Offset Carrier (BOC) signals, and then extended also to Multiplexed Binary Offset Carrier (MBOC), and to Alternate BOC (AltBOC) modulated signals. As a first analysis, the correlation peaks affected by the proposed threat model are shown for the aforementioned signals, and some evaluations on the parameters space are carried out. In order to evaluate the effect of deformations on the performance of a GNSS receiver, the tracking error behavior is studied for two types of discriminator (early late, double delta) and different correlators' spacing.