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.

Real-time assessment of GNSS observation noise with single receivers

Abstract: Stochastic modelling is critical in GNSS data processing. Currently, GNSS data processing commonly relies on the empirical stochastic model which may not reflect the actual data quality or noise characteristics. This paper examines the real-time GNSS observation noise estimation methods enabling to determine the observation variance from single receiver data stream. The methods involve three steps: forming linear combination, handling the ionosphere and ambiguity bias and variance estimation. Two distinguished ways are applied to overcome the ionosphere and ambiguity biases, known as the time differenced method and polynomial prediction method respectively. The real time variance estimation methods are compared with the zero-baseline and short-baseline methods. The proposed method only requires single receiver observation, thus applicable to both differenced and un-differenced data processing modes. However, the methods may be subject to the normal ionosphere conditions and low autocorrelation GNSS receivers. Experimental results also indicate the proposed method can result on more realistic parameter precision.

Airport Surface Movement - Performance Requirements, Architecture Considerations & Integrity Algorithms

Abstract: Satellite Navigation has become increasingly important in the optimisation of efficiency and safety within the aviation industry. ANASTASIA (Airborne New and Advanced Satellite techniques and Technologies in A System Integrated Approach) is a European Commission project within the Sixth Framework Program, with the basic objectives to define and implement future (beyond 2010) communication and navigation avionics based on satellite services. The objectives are to be achieved by exploiting the multi-constellation and multi-frequency architectures in combination with multiple onboard sensors, to provide a worldwide gate-to-gate service. Included in the objectives is a study of the most stringent navigation system performance requirements for a surface movement functionality under zero visibility conditions. This paper reviews existing navigation system performance requirements and compares them with those derived in this paper based on operational requirements, for each airport category. The stringency of the performance requirements suggests that the code-based GBAS architecture currently under development for CAT III landings may not be able to meet all the requirements of surface movement, and that carrier-phase based techniques may be required. In order to address the very stringent integrity requirements of surface movement, this paper uses a novel carrier-phase RAIM (C-RAIM) algorithm developed at Imperial College London, based upon a multiple set separation method with a multiple failure detection and exclusion capability [1]. The C-RAIM algorithm performance is dependent upon the range measurement uncertainties. For relative or differential measurements (e.g. GNSS augmented by GBAS), uncertainties in the measurements by the reference station and the user, as well as the error decorrelation between these measurements contribute to the overall measurement uncertainty at user level. The principal sources of uncertainty are noise, multipath, the troposphere and the ionosphere, the latter being of particular concern for surface movement. In order to accurately determine the ionosphere error residuals in real-time, and hence mitigate integrity risks and optimise availability, this paper develops a ground-based monitoring architecture, which we have called Extended GBAS (E-GBAS), based upon a modified GBAS CAT III architecture. The performance of the C-RAIM algorithm is analysed, using as input the ionosphere uncertainty provided by the E-GBAS, taking into account the specificities of the airport environment. Initial results suggest that the CRAIM algorithm, in combination with the E-GBAS architecture, will be able to meet the surface movement performance requirements. A value added outcome is that when used in combination with a state-of-the-art codebased architecture, the E-GBAS monitoring architecture has the potential to meet the navigation system performance requirements for CAT III landings.

Improved GNSS-based indoor positioning algorithm for mobile devices

Abstract: The widespread use of global navigation satellite system (GNSS) receiver in mobile devices induces the adoption of effective GNSS-based indoor positioning algorithms exploiting low-cost hardware. In a previous study, we proposed a new architecture for indoor positioning system to estimate the user position by utilizing the pseudoranges from the smartphone-embedded GNSS module. The advantages of such a system are low cost and low requirements in terms of hardware-level modification for end users. However, all end users and most application developers do not have permission to read the pseudoranges from the embedded GNSS modules. Instead of pseudoranges, the user positions are easily obtained from the GNSS module in any mobile device. Thus, we further improve our positioning algorithm based on the position obtained from the embedded GNSS module rather than the pseudoranges. This position does not correspond to the true one since the indoor signal is non-line-of-sight. Thus, it is named the pseudo-position. The key to the improved algorithm is that the distances from the user terminal to the indoor transmitting antennas are calculated using the differences between the position of the outside antenna and the pseudo-position. The algorithm is tested using a simulated GNSS-based indoor positioning system which is implemented on a GNSS software receiver. The simulation results show that the indoor positioning system is able to provide horizontal positioning with meter-level accuracy in both static and dynamic situations. Additionally, the proposed method improves the robustness of the indoor positioning system to the non-synchronization measurements.