Fundamentals of Satellite Navigation. GPS Systems Segments. GPS Satellite Signal Characteristics and Message Formats. Satellite Signal Acquisitions and Tracking. Effects of RF Interference on GPS Satellite Signal Receiver Tracking. Performance of Standalone GPS. Differential GPS. Integration of GPS with other Sensors. Galileo. The Russian GLONASS, Chinese Bediou, and Japanese QZSS Systems. GNSS Markets and Applications.

Understanding GPS : principles and applications

One of the key approaches to monitor the integrity of Global Satellite Navigation Systems (GNSS) is receiver autonomous integrity monitoring (RAIM). Existing RAIM algorithms utilise two tests in the position domain (for RAIM availability) and measurement domain (for failure detection). This paper proposes an alternative RAIM algorithm, which is based entirely in the measurement domain. This algorithm can be used for sensitivity analyses to support performance specification and system design. It can also be used during actual flight operations where the trigger is the phase of flight and its required navigation performance (RNP) parameters. This is made possible by computationally efficient calculation of the chi-squared parameters. The algorithm reverts to the current approach if the phase of flight is unknown. Simulation results for non-precision approach (NPA) have been used to demonstrate the effectiveness of the proposed algorithm.

A measurement domain receiver autonomous integrity monitoring algorithm

Disclosed is a method for providing a Global Navigation Satellite System (GNSS) navigation position solution with guaranteed integrity in non-controlled environments, the method including processing a (GNSS) signal including multiple satellites generating at least one signal to obtain carrier phase and pseudorange measurements; pre-processing the measurements to detect and characterize local errors in the measurements, wherein the local errors cannot be ascertained a priori, the characterization including providing error bounds estimated by measuring the carrier phase and pseudoranges measurements, thereby providing a set of measurements rejections when the characterization is not possible; and using the estimated error bounds, together with error bounds provided by the GNSS signal concerning satellite and ionospheric errors, to build in each measurement an estimated noise level in the measurements as input to a weighted Receiver Autonomous Integrity Monitoring (RAIM) algorithm in order to compute position coordinates and associated protection levels in the non-controlled environments.

Gnss navigation solution integrity in non-controlled environments

Global Navigation Satellite System (GNSS) Receiver Autonomous Integrity Monitoring (RAIM) is essential for safety-of-life and liability critical applications. This paper discusses two fundamentally different ways to assess the integrity risk of an operation with RAIM, based on a different amount of information available : the expected (or average) performance that is computed using the GNSS models only and the real-time (or actual) performance, which also uses information on the internal status of a GNSS receiver. It is shown both theoretically and by simulation that the real-time integrity risk significantly exceeds the expected risk after the detection and exclusion of a failing satellite. Therefore, while most published RAIM algorithms base their performance assessment on the expected performance only, this is only correct when the requirements allow the risk evaluation to be averaged over multiple operations. However, when the GNSS integrity requirement is to be applied on a ‘ per operation’ basis, real-time integrity measures are more appropriate.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0373463308005158

On the Availability of Fault Detection and Exclusion in GNSS Receiver Autonomous Integrity Monitoring

https://nottingham-repository.worktribe.com/preview/894312/Progress%20in%20Aerospace%20Sciences%20-%20GNSS%20Paper_.pdf

Global navigation satellite systems performance analysis and augmentation strategies in aviation

Working Group 5 of RTCA Special Committee (SC )-159 has spent the past several years working on the problem of GPS fault detection and exclusion (FDE) for a primary-means navigation system that can support oceanic en route through nonprecision approach modes of flight. The results of this working group's activities have been incorporated into RTCA/DO-229, Minimum Operational Performance Standards (MOPS) for GPS/WAAS Airborne Equipment, and will also serve as a baseline for the GPS/GLONASS and GPS/INS MOPS. The purpose of this paper is to provide a history of the development of the FDE requirements, algorithms, and test procedures, as well as a summary of the main issues addressed by the GPS Integrity (FDE) Working Group.

Summary of RTCA SC-159 GPS Integrity Working Group activities

In 1999, the FAA requested that RTCA SC-159 address
one of the recommendations from the study performed by
the Johns Hopkins University (JHU) Applied Physics Lab
(APL) on the use of GPS and augmented GPS for aviation
applications. This recommendation was to investigate
methods to improve Receiver Autonomous Integrity
Monitoring (RAIM) and Fault Detection and Exclusion
(FDE) algorithms. In response to the FAA request, an
Ad-hoc Working Group was formed within SC-159.
Although this paper mainly summarizes the analyses
performed by the authors in support of the Ad-hoc Working Group, it also includes deliberations with other
members of the Working Group.
This paper covers five areas. First, the paper analyzes the
availability of the RAIM/FDE function based on the GPS
Standard Positioning Service (SPS) Performance Standard
recently updated by DoD to compare the results with
those obtained by the JHU/APL study. Second,
alternative autonomous integrity monitoring methods are
evaluated and compared with the conventional snapshot-
based RAIM. Third, an investigation is performed to
determine if new RAIM and FDE availability criteria that
are consistent with operational requirements would
provide higher availability. Fourth, the paper revisits
FDE availability requirements and discusses how the
requirements could be made less difficult to meet.
Finally, it describes the findings of the Ad-hoc Working
Group based on the GPS SPS Performance Standard.

Analysis Performed in Support of the Ad-Hoc Working Group of RTCA SC-159 on RAIM/FDE Issues

This paper examines GPS receiver autonomous integrity monitoring (RAIM) availability for supplemental navigation based on the approximate radial-error protection (ARP) method. This method applies ceiling levels for the ARP figure of merit to screen out bad detection geometries under worst-case bias conditions. The ARP criterion value for each phase of flight is based on the integrity specifications stated in the RTCA Special Committee (SC)-159 supplemental Minimum Operational Performance Standards (MOPS) for GPS.



Applying the ARP criterion, extensive analysis was performed to determine the availability of RAIM over the conterminous United States, North Atlantic, Europe, Central East Pacific, and North Pacific during en route, terminal, and nonprecision approach phases of flight. The 21 primary, optimal 21, and optimized 21 + 3 GPS constellations were examined. The results demonstrate that RAIM is not available 100 percent of the time, even with 24 operational satellites. This is because there are times when only 4 satellites are visible, preventing RAIM detection altogether, and other times when the geometry of the visible satellites has an ARP that exceeds the ARP ceiling value.

RAIM availability for supplemental GPS navigation

Analysis of the RTCA Special Committee (SC)-159 baseline fault detection and exclusion (FDE) algorithm has been performed to determine whether a combined GPS/GLONASS system could satisfy availability requirements for a primary-means air navigation system. The results presented in this paper are based on work performed in support of the RTCA SC-159 GPS/GLONASS working group.



These results demonstrate a substantial improvement in the availability of integrity over GPS alone, even if only a partial GLONASS constellation were to be available. Satellites were removed from both constellations to simulate operation under worst-case conditions. It appears that an integrated GPS/GLONASS system could meet the availability requirement for a primary-means air navigation system, even in cases where a number of satellites are out of service. Availability results are provided for oceanic, domestic en route, terminal, and nonprecision approach phases of flight.

Fault detection and exclusion performance using gps and glonass

The availability of the Global Positioning System (GPS) for airborne applications is driven by the accuracy, integrity, and continuity of the system. The International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPS) for Global Navigation Satellite Systems (GNSS) describe these requirements for each phase of flight [ICAO, 2000]. The availability requirement is provided as a range of values instead of one specific number so there is flexibility for the intended operation, traffic density, complexity of airspace, and availability of alternative navigation aids. Individual countries need to determine what level of implementation of satellite navigation is acceptable for their airspace. This paper examines the various options available for GNSS, ranging from standalone use of the signal to augmentation systems involving the use of differential corrections.This paper also discusses systems that the U.S. and several other countries have implemented to disseminate information regard...

Karen L. Van Dyke

Papers

Summary of RTCA SC-159 GPS Integrity Working Group activities

Analysis Performed in Support of the Ad-Hoc Working Group of RTCA SC-159 on RAIM/FDE Issues

RAIM availability for supplemental GPS navigation

Fault detection and exclusion performance using gps and glonass

GPS Availability and Outage Reporting for Aviation Applications