GNSS augmentation

About: GNSS augmentation is a research topic. Over the lifetime, 2478 publications have been published within this topic receiving 28513 citations. The topic is also known as: SBAS & Satellite Based Augmentation System.

GNSS receiver performance in urban environment: Challenges and test approaches for automotive applications

Abstract: In the modern automotive industry, the wide variety of Intelligent Transport System (ITS) services needs a positioning unit. The core of such unit is a Global Navigation Satellite System (GNSS) receiver hybridized or assisted by other sensors or data. In harsh environments, such as urban scenarios, the testing and performance assessment of these terminals is of paramount importance for ITS applications. In fact such environments are very challenging for the GNSS core unit. This paper proposes some test procedures suitable to assess the performance of GNSS receivers, as part of an hybridyzed positioning unit, in urban scenarios. The benefits of a GNSS receiver based on the Software Defined Radio (SDR) technology is exploited by presenting a set of results obtained on field tests.

Procedure for guiding an aircraft in the approach phase and corresponding ground beacon

Abstract: The invention relates to a procedure for guiding an aircraft in the approach phase comprising of receiving information on a predefined approach path, this information being contained in a message M 4 originating from a ground beacon transmitting on the same transmission channel as that of a beacon of a GBAS type positioning accuracy augmentation system, receiving differential positioning radio satellite signals, and correction information from these satellite radio signals in the form of a message M 1 ′ originating from a ground central station of an SBAS type positioning accuracy augmentation system, via geostationary satellites of this augmentation system, calculating a corrected position based on the positioning signals and correction information, calculating an elevation and horizontal guidance deviation of the aircraft relative to the predefined approach path, based on the corrected position and information on the predefined approach path.

Investigation on Reference Frames and Time Systems in Multi-GNSS

Abstract: Receivers able to track satellites belonging to different GNSSs (Global Navigation Satellite Systems) are available on the market. To compute coordinates and velocities it is necessary to identify all the elements that contribute to interoperability of the different GNSSs. For example the timescales kept by different GNSSs have to be aligned. Receiver-specific biases, or firmware-dependent biases, need to be calibrated. The reference frame used in the representation of the orbits must be unique. In this paper we address the interoperability issues from the standpoint of a Single Point Positioning (SPP) user, i.e., using pseudoranges and broadcast ephemeris. The biases between GNSSs timescales and receiver-dependent biases are analyzed for a set of 31 MGEX (Multi-GNSS Experiment) stations over a time span of more than three years. Time series of biases between timescales of GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), Galileo, BeiDou, QZSS (Quasi-Zenith Satellite System), SBAS (Satellite Based Augmentation System) and NAVIC (Navigation with Indian Constellation) are investigated, in addition to the identification of events like discontinuity of receiver-dependent biases due to firmware updating. The GPS broadcast reference frame is shown to be aligned to the one (IGS14) realized by the precise ephemeris of CODE (Center for Orbit Determination in Europe) to within 0.1 m and 2 milliarcsec, with values dependent on whether IIR-A, IIR-B/M or IIF satellite blocks are considered. Larger offsets are observed for GLONASS, up to 1 m for GLONASS K satellites. For Galileo the alignment of the broadcast orbit to IGS14/CODE is again at the 0.1 m and several milliarcsec level, with the FOC (Full Operational Capability) satellites slightly better than IOV (In Orbit Validation). For BeiDou an alignment of the broadcast frame to IGS14/CODE comparable to GLONASS is observed, regardless of whether IGSO (Inclined Geosynchronous Orbit) or MEO (Medium Earth Orbit) satellites are considered. For all satellites, position differences according to the broadcast ephemeris relative to IGS14/CODE orbits are projected to the radial, along-track and crosstrack triad, with the largest periodic differences affecting mostly the along track component. Sudden discontinuities at the level of up to 1 m and 2–3 ns are observed for the along-track component and the satellite clock, respectively. The time scales of GLONASS, Galileo, QZSS, SBAS and NAVIC are very closely aligned to GPS, with constant offsets depending on receiver type. The offset of the BeiDou time scale to GPS has an oscillatory pattern with peak-to-peak values up to 100 ns. To characterize receiver-dependent biases the average of six Septentrio receivers is taken as reference, and relative offsets of the other receiver types are investigated. These receiver-dependent biases may depend on the individual station, or for the same station on the update of the firmware. A detailed calibration history is presented for each multiGNSS station studied.

Satellite Selection for Multi-Constellation SBAS

Abstract: The incorporation of multiple constellations into satellite based augmentation systems (SBAS) may lead to cases where there are more corrected satellites in view than a receiver has tracking channels. This paper addresses two related topics: identifying the most important satellites to track in order to provide availability; and identifying a recommended number of channels. Previously, the SBAS minimum operational performance standards (MOPS) specified a minimum number of channels required for the user receiver. It is possible to obtain significantly worse availability with this minimum number than with the all-in-view solution when employing a poor satellite selection algorithm. Alternatively, it is possible to achieve high availability with fewer than the minimum number of channels and a very good selection algorithm. This paper describes example selection methods that achieve high availability. It further describes a method to specify performance instead of a minimum hardware channel capacity. This form of specification allows for greater flexibility in receiver design. Manufacturers would be allowed to choose between more channels combined with a simpler algorithm versus fewer channels and a more sophisticated algorithm.

A Multisensor Navigation System Based on an Adaptive Fault-Tolerant GOF Algorithm

Abstract: This paper describes an adaptive fault-tolerant multisensor integrated navigation system. The proposed system uses a decentralized filtering architecture to fuse inertial navigation system (INS), GNSS, and $Locata$ sensor subsystems. In order to improve system accuracy, the global optimal filtering (GOF) algorithm is implemented. The GNSS and $Locata$ subsystems are separately integrated with the INS to obtain the local prediction and local estimation based on the GNSS/INS and $Locata$ / INS combinations. The GOF algorithm is then applied to fuse the local and global information to generate the optimal state estimation of the GNSS/ Locata /INS navigation system. The adaptive fault-tolerant algorithm is based on the innovation covariance discrepancy, which mainly adapts to the changes in sensor measurement statistical properties and mitigates the adverse influence caused by these changes. It is found that the GOF algorithm does improve the accuracy of the navigation solution compared with conventional filtering. To evaluate the fault-tolerant ability of the proposed system, a series of GNSS failures is simulated. The results show that the proposed system can mitigate the effect of the failures, which verify the higher reliability and fault-tolerant capability of the proposed system.