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.

Assessment and analysis of radio frequency compatibility among several global navigation satellite systems

Abstract: The increasing number of new global navigation satellite systems (GNSS) signals leads to more interference effects on existing and upcoming navigation signals in the same frequency band. GNSS radio frequency compatibility has become a matter of great concern for the system providers and user communities. This study describes a comprehensive methodology for radio frequency compatibility assessment, and analyses the intersystem interference among several GNSS systems. Firstly, the methodology is presented, considering the geometry-dependent and time-varying terms such as space constellation, signal modulation, emission power level, space loss, satellite antenna gain and user receiver characteristic. Then, the intersystem interference is computed for signals where GPS, Galileo, Compass and SBAS systems are sharing the same frequency band. The analysis results show that interference effects on GNSS user receiver from the above-mentioned systems are acceptable. The introduction of Compass system can provide a sound basis for compatibility with GPS and Galileo.

Gnss signal processing with delta phase

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.

Analysis of global navigation satellite system position deviation under spoofing

Abstract: The position deviation in global navigation satellite system (GNSS) positioning, which is subject to spoofing, is analysed. A spoofer transmits GNSS-like signals to a navigation receiver and may cause a significant position deviation in navigation computation. Although GNSS receivers can be equipped with certain receiver autonomous integrity monitoring (RAIM) schemes to provide fault detection and isolation functions, it is possible that the misleading information because of spoofers may enter a GNSS receiver without being detected. As spoofers may inject erroneous pseudo-range measurements to the navigation receiver with a false message, it is important to assess the spoofing effect on the resulting position. An optimisation approach is adopted to determine the worst-case misleading message and the resulting position deviation. A vulnerability index against spoofing is defined for the assessment of the position deviation in a spoofed environment.

Validation of the Airframe Multipath Error Allocation for Local Area Differential GPS

Abstract: The International Civil Aviation Organization (ICAO) Global Navigation Satellite System (GNSS) Panel (GNSSP) has developed Standards and Recommended Practices (SARPs) for Ground Based Augmentation Systems (GBAS) and Space Based Augmentation Systems (SBAS). The RTCA Special Committee 159, Working Group 4A (WG-4A) has also developed the Minimum Operational Performance Standards (MOPS) for airborne GPS/Local Area Augmentation System (LAAS) and GPS/Wide Area Augmentation System (WAAS) receivers. These standards include an airborne error allocation for airframe multipath defined by a common error model. This model is intended to apply to all GBAS (i.e. LAAS) or SBAS (i.e. WAAS) receivers installed on any aircraft within a reasonable set of installation guidelines. The motivation for standardizing the error model is to fix the allocation for receiver tracking performance and limit test requirements to evaluating that tracking performance. Testing of airframe multipath on each aircraft model would be very impractical and expensive. This paper describes the validation activity that has been done to show that the standard error model for airframe multipath is adequate. The standard multipath error model is presented and discussed in the context of the allocation of SARPs and MOPS requirements. The expected magnitude of airborne multipath based on theoretic considerations is discussed. The paper then presents the methods used to estimate the multipath error as well as the difficulties experienced in isolating the multipath error component from in-flight measurements. The in-flight measurements were recorded during long duration flights of a number of aircraft including the Boeing 727, 737, 747, 757, 767 and 777 airplanes. The paper concludes with the results and interpretation of the validation activities. This activity is significant because it represents the most comprehensive study of airframe multipath on commercial air transport airplanes to date. The study shows that for commercial applications, an allocation for airborne multipath that is independent of the specific aircraft type is feasible.

Space Weather influence on satellite based navigation and precise positioning

Abstract: Global Navigation Satellite Systems (GNSS) are widely used to measure positions with accuracies ranging from a few mm to about 20 m. The effect of the Earth ionosphere on GNSS signal propagation is one of the main error sources which limits the accuracy and the reliability of GNSS applications. In particular, disturbed Space Weather conditions can be the origin of strong variability in the ionosphere Total Electron Content (TEC) which itself degrades the accuracy of GNSS applications. Space Weather effects on GNSS depend very much on the type of application. In this paper, we discuss the effects of Space Weather conditions on differential positioning with the Differential GPS (DGPS) technique and on relative positioning with the Real Time Kinematic (RTK) technique. We show that DGPS is affected by medium to large-scale gradients in TEC mainly observed at solar maximum when RTK will be degraded by smaller-scale ionospheric variability due to scintillations, TEC noise-like behaviour and Travelling Ionospheric Disturbances