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REAL-TIME ARAIM USING GPS, GLONASS, AND GALILEO
Title
REAL-TIME ARAIM USING GPS, GLONASS, AND GALILEO
Creator
Cassel, Ryan
Date
2017, 2017-05
Description
Since the inception of GPS, satellite navigation has been a widely used means of navigation for both military and civilian users on the ground...
Show moreSince the inception of GPS, satellite navigation has been a widely used means of navigation for both military and civilian users on the ground and in the air. GPS is capable of providing highly accurate positioning and timing information to users around the globe. However, for certain applications, providing high-accuracy position estimates is not sufficient. Because satellites are susceptible to faults, the safety, or integrity, of the position estimates is also of concern, especially in civilian aviation where safety is critical. As such, receiver autonomous integrity monitoring (RAIM) can be used in order to detect and potentially exclude these faults and guarantee the safety of the position estimate. RAIM has been capable of supporting horizontal aircraft navigation using GPS for decades and has proven to be a useful tool. Now, as more global navigation satellite systems (GNSS) become available, the potential for advanced RAIM (ARAIM) to support vertical guidance for aircraft using multiple constellations has become an area of great interest. In this work, the ARAIM methodology is discussed, and the procedure is outlined, including protection level calculation, fault detection, and exclusion. The procedure is then implemented in a real-time ARAIM prototype. While GPS and Galileo aim to provide worldwide coverage for vertical guidance by 2020 when Galileo is fully operational, ARAIM performance can be examined at present using the current full-strength GPS and GLONASS constellations. This prototype performs position estimation and ARAIM using measurements from the current GPS, GLONASS, and partial Galileo constellations. ARAIM results in a variety of different GNSS scenarios are examined. Furthermore, this work investigates two methods of improving the computational efficiency of the ARAIM algorithm: satellite selection and fault mode grouping.
M.S. in Mechanical and Aerospace Engineering, May 2017
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High-integrity modeling of non-stationary Kalman Filter input error processes and application to aircraft navigation
Title
High-integrity modeling of non-stationary Kalman Filter input error processes and application to aircraft navigation
Creator
Gallon, Elisa
Date
2023
Description
Most navigation applications nowadays rely heavily on Global Navigation Satellite Systems (GNSSs) and inertial sensors. Both of these systems...
Show moreMost navigation applications nowadays rely heavily on Global Navigation Satellite Systems (GNSSs) and inertial sensors. Both of these systems are known to be complementary, and as such, their outputs are very often combined in an extended Kalman Filter (KF) to provide a continuous navigation solution, resistant to poor satellite geometry, as well as radio frequency interference. Additionally, recent development in safety critical applications (such as aviation) revealed the performance limitations of current algorithms (Advance Receiver Autonomous Integrity Monitoring - ARAIM) to vertical guidance down to 200 feet above the runway (LPV-200). When nominal constellations are depleted, LPV-200 can only sparsely be achieved. Exploiting satellite motion in ARAIM (for instance using a KF) could help alleviate those limitations, but would require adequate modeling of the errors, including the error's time correlation.Power Spectral Density (PSD) bounding is a methodology that provides high integrity, time correlated error models, but this approach is currently limited to stationary errors (which is rarely the case with real data), and has never been applied to navigation errors. More generally, no high integrity, time correlated error models have ever been derived for navigation errors.As a result, in the first part of this thesis, a methodology for high integrity modeling of time correlated errors is introduced. The PSD bounding methodology is extended to both stationary and non-stationary errors. In the second part of this thesis, these methodologies are applied to the 3 main error sources impacting iono-free GNSS measurements (orbit and clock errors, tropospheric errors and multipath), as well as to inertial errors.The methodology introduced in this dissertation provides high integrity time correlated error models and is applicable to any type of applications where high integrity is required (e.g. Differential GNSS - DGNSS, Aircaft Based Augmentation System - ABAS, Ground Based Augmentation System - GBAS, Space Based Augmentation System - SBAS, etc...). Additionally, the error models derived here are not only limited to high integrity applications, but could also be used in applications were the correlation over time of the errors plays an important role (such as any KF integration).In the last part of this dissertation, we focus on a specific safety critical application: aviation, and in particular ARAIM. The dissertation is concluded with an assessment of the performance improvements provided by recursive ARAIM, using those bounding dynamic error models, with respect to those models, used for baseline snapshot ARAIM. Additionally, a sensitivity analysis is performed on each of the error model parameters to assess which of them impacts the KF performance (i.e. covariance) the most.
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Ground Monitors to Support Navigation Operations of ARAIM and GBAS
Title
Ground Monitors to Support Navigation Operations of ARAIM and GBAS
Creator
Patel, Jaymin Harshadkumar
Date
2023
Description
Receiver Autonomous Integrity Monitoring (RAIM) currently provides safehorizontal navigation guidance to en route civil aircraft using the GPS...
Show moreReceiver Autonomous Integrity Monitoring (RAIM) currently provides safehorizontal navigation guidance to en route civil aircraft using the GPS L1 frequency. As an evolution of RAIM, Advanced RAIM (ARAIM) is being developed to provide vertical guidance in addition to horizontal using multiple constellations and dual frequency thus facilitating precision approach without ground support for civil aircraft. However, navigation guidance during zero-visibility (Category III) precision landing requires an additional support in real time from a Ground Based Augmentation System (GBAS). To improve the aircraft navigation solution, GBAS broadcasts a differential correction and monitors any failure on transmitted satellite signals. This dissertation contributes to ARAIM and GBAS to improve existing navigation operations in order to enable precision approach and landing.The achievable performance of ARAIM is highly dependent on the assumptionson a constellation’s nominal Signal-In-Space (SIS) error models and a priori fault probability. In the framework of ARAIM, an Integrity Support Message (ISM) is envisioned to carry the required SIS error-model parameters and fault statistics for users. The ISM is generated and validated through offline monitoring, and disseminated along the navigation message. The first dissertation contribution is to provide necessary satellite positions and clock biases as a truth product to evaluate nominal SIS range errors (SISREs). An estimator is developed to generate accurate ephemeris parameters to provide these truth products. The estimator’s performance is demonstrated for the Global Positioning System (GPS) constellation by utilizing the International GNSS Service (IGS) ground network to collect dual-frequency raw GPS code and carrier phase measurements. The resulting SISREs from the estimator are predicted to have a standard deviation of 0.5 m. When estimated ephemeris parameters and clock biases are compared with precise IGS orbit and clock products, the resulting SISREs are within ±2! at all times. In the second contribution, a new approach is proposed to generate the ISM by modeling the ephemeris parameter errors directly. In preliminary analysis, an ephemeris parameter error model is developed for the broadcast GPS legacy navigation message (LNAV) under nominal conditions. Then, the proposed approach is demonstrated to provide the nominal bias and standard deviation on GPS SISREs.As a part of fault monitoring in the GBAS, a ground monitor is developedto detect ephemeris failures, incorrect broadcast satellite positions, and hazardous ionosphere storms using either single- or dual frequency. The monitor also addresses the challenge of fault-free differential correction when satellites are rising, newly acquired, and re-acquired. The monitor utilizes differential code and carrier phase measurements across multiple reference receiver antennas as the basis for detection. Finally, the analytical performance of the monitor is demonstrated to meet Category III precision approach and landing requirements.
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