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In 2020 several member states initiated at IMO forum (NCSR subcommittee) a process to create a single set of generic performance standards consolidating all existing performance standards for shipborne satellite navigation system receiver equipment without creating any new requirements. After over 4 years the resultant generic framework for GNSS/RNSS subsystems has not been adopted yet and awaits further amendments. Analysis of the proposed standards with stress on harmonization issues of the existing, IMO recognized, global and regional navigation satellite systems and the expected impact of these generic standards of satellite navigation receivers on the maritime user are presented in this paper. Additionally the strengths, weaknesses, opportunities, and threats awaiting maritime or shipborne GNSS/RNSS equipment standardization process are outlined in the paper. [ABSTRACT FROM AUTHOR]

According to aviation minimum operational performance standards (MOPS), protection levels for satellite-based augmentation systems (SBASs) are to be computed as the product of the estimated standard deviation of errors and a scaling, or K-factor. MOPS recognized that K-factors were originally chosen to be consistent with certain assumptions that may not hold under all conditions. Considering the limited applicability of aviation-based K-factors, it will be important to identify a more rigorous method for deriving new SBAS applications for road, rail, or maritime use. Here we describe an innovative method applicable to any integrity risk (e.g., at 10-7 for aviation or 10-5 for maritime applications) and time interval T (e.g., 150 seconds to 1 hour for aviation or 3 hours for maritime use). This new method relies on rigorous probability justification. No restrictive assumptions are needed for the time correlation pattern of the errors. The method is easy-to-implement and applicable to any type of integrity risk or time interval T. [ABSTRACT FROM AUTHOR]

Ionospheric scintillation is one of the main error sources of Global Navigation Satellite System (GNSS) positioning. The presence of scintillation may result in cycle slips, measurement errors or even losses of lock on satellites, eventually leading to complete failure of positioning. Typically, scintillation parameters S4 and σϕ are used to characterize amplitude and phase scintillation, respectively. However, the scintillation parameters can only be generated from data with a frequency of at least 1 Hz. Rate of change of total electron content index (ROTI) is often used as a proxy for scintillation parameters, which can be obtained from 1/30 Hz data. However, previous research has shown the inefficiency of ROTI to represent scintillation. Therefore, the multipath parameter (MP) has been proposed as another proxy for scintillation parameters, which can also be obtained from 1/30 Hz data. In this paper, both MP and ROTI (standard parameters) were used to mitigate scintillation effects on precise point positioning (PPP). To evaluate the effectiveness of MP and ROTI in mitigating scintillation effects, S4 and σϕ were also used for comparison and validation. Three strategies are proposed: (1) remove all observations from the satellite that is most affected by scintillation; (2) remove the scintillation-affected observations; (3) weight the measurement noise matrix in the Kalman Filter (KF) process. The results show that the observation removal and weighting strategies are considerably more effective than the satellite removal strategy. The results also show that the improvement of PPP outputs reaches 93.1% and the performance of standard parameters is comparable to that of scintillation parameters in the observation removal and weighting strategies. [ABSTRACT FROM AUTHOR]

The primary means for electronic position fixing in use in contemporary maritime transport are shipborne GPS (Global Positioning System) receivers or DGPS (Differential GPS) receivers. More advanced GNSS (Global Navigation Satellite System) or RNSS (Regional Navigation Satellite Systems) receivers are able to process combined signals from American GPS, Russian GLONASS, Chinese Beidou (BDS), European Galileo, Indian IRNSS, and Japan QZSS. Satellite-based augmentation systems (SBAS) are still not commonly used in the maritime domain, especially onboard vessels certified under international SOLAS convention. The issues and weaknesses of existing International Maritime Organization recommendations, guidelines, requirements, performance standards, and policies on GNSS shipborne sensors are discussed and presented in the paper. Many problems that have already been dealt with in other means of transportation are still to be solved in the maritime domain. The integrity monitoring is addressed as the main issue, and recommendations based on solutions implemented in aviation and the latest research are proposed. Finally, the strengths, weaknesses, opportunities, and threats awaiting maritime GNSS standardization process are outlined. [ABSTRACT FROM AUTHOR]

Advanced receiver autonomous integrity monitoring (ARAIM) is under development to support both lateral and vertical guidance. A key component of ARAIM is the integrity support message (ISM), which contains validated input parameters including the probabilities of satellite and constellation failure. A service commitment for the former is provided in the global positioning system (GPS) performance standards, whereas further commitments from GLONASS, Galileo, and Beidou are expected to follow. However, air navigation service providers may demand some flexibility in setting the ISM. This article presents a procedure for setting ISM parameters employing a means to determine the a priori probabilities using the Bayesian inference of a Poisson process model given in the literature. This method and a novel way to accumulate the service history are used to analyze the effects of satellite block and age. Results show that while the type and age of satellite are clearly drivers in the likelihood of a fault; such effects may be accounted for without significant impact on the broadcast values. This article also addresses the probability of unscheduled satellite outages using the new method. Finally, this article gives a high-level scheme of how the validity of the ISM parameters may be assured. [ABSTRACT FROM AUTHOR]

ABSTRACT Future Aircraft Surveillance Applications (ASA) systems for situational awareness applications (e.g., conflict detection and resolution, final approach and runway occupancy awareness, and airport surface situational awareness methods), airborne spacing applications, airborne separation applications, and self-separation applications will benefit from the introduction of Automatic Dependent Surveillance-Broadcast (ADS-B). An alternative ADS-B implementation, which transmits measurements from the Global Navigation Satellite System (GNSS) instead of aircraft state vectors and performance parameters in the current implementation, has been proposed previously to improve surveillance performance. This paper summarizes the proposed methodology, discusses its threat models and integrity aspects, and presents the initial flight test results of this alternative ADS-B implementation, along with a performance analysis. Copyright © 2013 Institute of Navigation [ABSTRACT FROM AUTHOR]

ABSTRACT Global navigation satellite system (GNSS) positioning is widely used in land vehicle and pedestrian navigation systems. Nevertheless, in urban canyons GNSS remains inaccurate due to building blockages and reflections, especially in the cross-street direction. Shadow matching is a new technique, recently proposed for improving the cross-street positioning accuracy using a 3D model of the nearby buildings. This paper presents a number of advances in the shadow-matching algorithm. First, a positioning algorithm has been developed, interpolating between the top-scoring candidate positions. Furthermore, a new scoring scheme has been developed that accounts for signal diffraction and reflection. Finally, the efficiency of the process used to generate the grid of building boundaries used for predicting satellite visibility has been improved. Real-world GNSS data has been collected at 22 different locations in central London to provide the first comprehensive and statistical performance analysis of shadow matching. Copyright © 2013 Institute of Navigation. [ABSTRACT FROM AUTHOR]

Tropospheric delay is a major error source that affects the performance of the Global Navigation Satellite Systems (GNSS) Real Time Kinematic (RTK) positioning especially for the medium/long-range baseline. Although high precision tropospheric delay can be estimated by GNSS carrier phase measurement, together with position and ambiguity, a relatively long period of convergence time is necessary. In this study, we develop a new GPS/BDS RTK algorithm constrained with a tropospheric delay parameters from Numerical weather prediction (NWP) model for medium/long-range baselines. The accuracy of the tropospheric delays derived from NWP is assessed through comparisons with the results of GAMIT (GNSS at MIT). The positioning performance with standard GPS RTK, standard GPS/BDS RTK, the developed NWP-constrained GPS RTK and NWP-constrained GPS/BDS RTK over medium/long-range baselines are compared in terms of the initialization time and the positioning accuracy. Experiment results show that the mean differences between the NWP and GAMIT zenith tropospheric delay (ZTD) are between −5.50 mm and 5.60 mm, and the RMS values of the NWP ZTD residuals are from 24.02 mm to 32.62 mm. A reduction in the initialization time of over 41% and 58% for medium- and long-range baselines can be achieved with the NWP-constrained RTK (both GPS alone and GPS/BDS RTK solutions) compared to the standard RTK solution, respectively. An improvement of over 30% can be found with the GPS/BDS RTK compared with that of the GPS alone RTK for both standard and the NWP-constrained modes. The positioning precision of NWP-constrained GPS/BDS RTK is better than 3 cm in the horizontal direction and better than 5 cm in the vertical direction, which satisfies the requirement of the precise positioning service. [ABSTRACT FROM AUTHOR]

We present a statistical detection test for GPS multipath based on a one-way ANOVA method. Given an antenna array with a multi-channel software GPS receiver in tracking mode, the signal from each channel is correlated with a reference signal in batches of one CA code period. The relative phase delay for the direct line-of-sight (DLOS) GPS signal from each antenna is then removed. Assuming the multipath and DLOS signal have different angles of arrival (AOA), the average correlator outputs are identical for all channels if no multipath is present. The ANOVA test is applied to detect the presence of multipath. Receiver operating characteristic (ROC) curves under various signal conditions are presented to assess the performance of the ANOVA method. Theoretical analysis and simulation results show that good detection performance can be achieved under most operating conditions using less than 10 CA code periods of data. The detection performance improves as the multipath delay time decreases. [ABSTRACT FROM PUBLISHER]