Global Navigation Satellite Systems Engineering, Policy, and Design
A new method for multipath rejection employs a multicorrelator-based GNSS receiver with an extended Kalman Filter (EKF) as an iterative solver, replacing the conventional delay locked loop (DLL) code tracking. The technique significantly reduces the positioning error and has low complexity. It can therefore be implemented in a real-time processing environment.
Ionospheric delay is the largest source of range error for GPS Standard Positioning Service (SPS) users, at least during local daytime when solar emissions enhance these delays.
By Inside GNSS
Ligado Networks had an early-year win in the form of a Federal Communications Commission denial of the National Telecommunications and Information Administration Stay Petition involving Ligado’s license for a terrestrial service in the mobile satellite services L-band. The company continues to roll toward deployment of a nationwide 5G network. While filings trickle in from the private sector, the feds work quietly behind the scenes on Congressional due-outs. In short, wheels big and small keep churning down the river to 5G.
By Dawn M.K. Zoldi (Colonel, USAF, Ret.)
Galileo satellites 5 and 6 (E18, E14) were declared unusable in February 2021 after reports indicating repeatable daily problems with RTK. This article explores the possible impact of deviant elliptical orbits on the performance of RTK and finds that there is no reason to expect any anomalies caused by high orbit eccentricity per se. Thus there is no reason to declare the satellites unhealthy.
The addition of alternative sensors such as cameras, magnetometers, and small ranging radios increases the likelihood of a mismodeled and/or faulty sensor, affecting the accuracy and performance of the overall navigation solution. Unlike two-sensor systems such as GPS-inertial integration, systems of three or more sensors present the problem of ambiguity as to which sensor is adversely affecting the solution. This presents the need for a robust framework that can maintain navigation integrity despite the additional sensor modalities.
In a GNSS spoofing attack, a terrestrial radio transmitter mimics GNSS signals at a greater signal strength than the actual system can transmit. In order to detect and mitigate a spoofing attack, it is important to know where a spoofing signal comes from and what it tries to accomplish for its ultimate neutralization.
Interference mitigation techniques should protect GNSS receivers from interference and jamming without biasing their final position, velocity and timing solution. This column analyses five popular interference mitigation techniques, including the Adaptive Notch Filter (ANF) and Pulse Blanking (PB), evaluating their impact on pseudoranges and on the final position and timing solution. Several GNSS modulations are considered, showing the advantage of using GNSS signals with similar spectral characteristics.
In the beginning, GPS was envisioned as a military program. A sign on the wall in the Joint Program Office where the system came into being during the early 1970s read: “The mission of this Program Office is to:
A Department of Homeland (DHS)-chartered May 2021 report concludes that PNT threat and resilience concerns are not as dire as some have made them out to be, and that funds for backup could be spent elsewhere. Why this runs counter to other recent government reports is not clear, nor is the fallout from this divergence of Congressionally mandated views. The Department of Transportation has distanced itself a bit from this report by the RAND Corporation—and even its issuer, the DHS, seems to have done so.
A new approach to achieving the safety needed for levels 3 and higher of autonomy builds on a thorough mathematical framework to support safety analysis, while delivering very tight position bounds.
A novel method to track Galileo E5 AltBOC signal phase adjusts and then combines the correlation results of the upper sideband and lower sideband signal to form a double-sideband correlation result, which is equivalent to AltBOC wideband receiving to some extent. Thus, a Galileo E5 wideband receiver can be achieved with only minor modification to a traditional GNSS single-sideband receiver. The method can be further applied to other binary offset carrier (BOC) signals.
By Inside GNSS
SAM PULLEN, Stanford University
A: Since at least 1997, the Global Positioning System (GPS) Control Segment (CS) has issued what are known as “Notice Advisor(ies) to NAVSTAR Users” or “NANU(s).”
By Inside GNSS
Multi-antenna carrier-phase differential GNSS (CDGNSS)-based pose (position and orientation) estimation aided by monocular visual measurements and a smartphone-grade inertial sensor form the core of a system designed for micro aerial vehicles. It can be applied generally for low-cost, lightweight, high-accuracy, geo-referenced pose estimation.
