With the escalating prevalence of in-band interference, the vulnerability of Global Navigation Satellite System (GNSS) receivers to potential jamming or spoofing threats has become a critical concern. The proliferation of GNSS repeaters, commonly known as meaconers (electronic devices that intercept GNSS signals, amplify them, and subsequently rebroadcast them) contributes to...
In the precise orbit determination (POD) processing, one of the critical issues is the modeling of non-conservative solar radiation pressure (SRP) forces acting on global navigation satellite systems (GNSS) satellites. However, for the third generation of BeiDou system (BDS-3) medium Earth orbit (MEO) satellites, the missing specular and diffuse reflection coefficients in the...
Low Earth Orbit (LEO) satellites are widely used in mobile communications. They can be used to provide navigation services by broadcasting navigation signals and augmentation information. However, it is extremely expensive to construct a mega constellation of LEO satellites equipped with navigation payloads. A better way would be making good use of the LEO communication...
Teunissen (J Geod 98(83):1–16, 2024) proposed the ambiguity-resolved (AR) detection theory for GNSS mixed-integer model validation. In this contribution, we study the performance of the AR detector through analysis and simulation experiments and compare it with the ambiguity-float (AF) and ambiguity-known (AK) detectors. We describe how the detectors can be implemented and how to...
Signal anti-jamming has always been a difficult problem in GNSS (global navigation satellite system) signal processing. There are many GNSS anti-jamming techniques in the existing research, which can achieve good results if the interferences are sparsely distinguishable in some signal feature domains. Specifically, the single antenna based anti-jamming techniques cannot deal with...
Integrated Water Vapor (IWV) is crucial in environmental research, offering insights into atmospheric dynamics. Direct IWV measurement is challenging, necessitating alternative estimation technologies. Existing methods including Global Navigation Satellite System (GNSS), radiosondes, water vapor radiometers (WVR), satellite remote sensing, and numerical weather models (NWM), have...
The real-time ionospheric data streams are continuously being provided by a number of International GNSS service analysis centers such as Centre National d’Etudes Spatiales (CNES), Chinese Academy of Sciences (CAS), Universitat Politècnica de Catalunya (UPC), and Wuhan University, however, the performance evaluation of these Real-Time Global Ionosphere Map (RT-GIM) products is...
Low-cost (LC) Global Navigation Satellite System (GNSS) receivers are argued as an alternative solution to geodetic GNSS counterparts for different applications. Single-frequency low-cost (SF-LC) GNSS receivers have been in the market for many years while their inability to acquire GNSS observations in second frequency limited their use. A few years ago, dual-frequency low-cost...
On February 6, 2023 the Kahramanmaraş Earthquake Sequence caused significant ground shaking and catastrophic losses across south-central Türkiye and northwest Syria. These seismic events produced ionospheric perturbations detectable in Global Navigation Satellite System (GNSS) total electron content (TEC) measurements. This work aims to develop and incorporate a near-real-time...
In this paper, we propose a novel algorithm for fast frequency and phase synchronization of high-stability oscillators synchronized with 1 PPS signal from satellite navigation systems. The algorithm uses a model of a control object in the space of state variables and controls the frequency of an oscillator operating in a phase-locked loop. A new element is the introduction to the...
The development of Global Navigation Satellite Systems (GNSS) results in large spatial geodetic networks with a distinct range of accuracy. Thus, classification of the GNSS stations is needed to determine which stations are appropriate for geodetic applications. Additionally, advanced Machine Learning (ML) techniques have been proposed. However, ML algorithms may sometimes be...
For about three decades, the Global Navigation Satellite System (GNSS) has been used for high-precision positioning in scientific and engineering applications, such as deformation monitoring for seismicity and volcano eruption. Such high-precision positioning applications require millimeter-level positioning accuracy. There are many man-made and natural reflective surfaces near...
Satellite signals from the Global Navigation Satellite System (GNSS) are refracted as they pass through the troposphere, owing to the variable density and composition of the atmosphere, causing tropospheric delay. Typically, tropospheric delay is treated as an unknown parameter in GNSS data processing. Given the growing need for real-time GNSS applications, accurate tropospheric...
The European Galileo High Accuracy Service (HAS) started to provide freely and openly accessible real-time precise satellite orbit, clock and code bias products to global users on January 24, 2023. Combined with the already running BeiDou PPP-B2b service, the launch of a variety of satellite-based PPP services provided more choices to users. However, different satellite-based PPP...
Following several performance enhancements, GPS has provided a stable signal-in-space range error (SISRE) of about 50 cm (RMS) for more than a decade. As of early 2024, a major SISRE reduction by about 30% could be noted that helps to maintain the competitiveness of GPS in comparison with the Chinese BeiDou system and reduces the performance difference with respect to the...
Un-differenced (UD) ambiguity resolution (AR) is widely applied since it can avoid wrong-fixing and fix the most of ambiguities. However, in the precise orbit determination (POD) solution using ground network only, the accuracy of float estimates is not sufficient for a direct UD AR, and thus double-differenced (DD) AR must be conducted first. It is demonstrated that integrating...
Ionospheric tomography offers three-dimensional (3D) description of the electron density distribution, enabling the direct incorporation of electron density data into the slant total electron content (STEC) computation. As a result, STEC derived from tomography helps mitigate the ionospheric delay experienced in the line of sight between global navigation satellite systems (GNSS...
Global Navigation Satellite Systems (GNSS) support numerous applications, including mission-critical ones that require high integrity for safe operations such as air, maritime, and land-based navigation. These applications require ensuring the upper bound of the positioning computation, including overbounding any assumptions made in positioning algorithms. One of the main...
Integer ambiguity resolution plays a key role in applications related to GNSS precise positioning. This contribution focuses on three commonly used integer estimators (IEs), i.e., integer rounding (IR), integer bootstrapping (IB) and integer least-squares (ILS). Contributions are mainly of four aspects. First, the objective function of IR and IB is given, respectively. Second, an...
Phase center offsets and variations (PCV) are common corrections applied to global navigation satellite system (GNSS) phase observations in the context of precise point positioning. Similar to PCV are group delay variations (GDV), which affect code observations. In this paper, absolute GDVs, which are independent of a reference antenna, are estimated as antenna- and frequency...
In this work we introduce the LAMBDA 4.0 toolbox, which provides an enhanced implementation for integer estimation, validation, and success rate evaluation. This free and open-source toolbox is a major update to LAMBDA 3.0 (2012), while it also integrates the functionalities from Ps-LAMBDA 1.0 (2013), thus respectively merging both estimation and evaluation capabilities. The new...
We present a new Global Navigation Satellite Systems (GNSS) positioning approach that utilizes low-rate Virtual Reference Station (VRS) data to achieve high-rate displacement monitoring. The method integrates tightly the VRS technology with asynchronous Real-Time Kinematic (RTK) method to overcome the limitation of VRS in high-rate structural health monitoring (SHM) applications...
The relative displacements of stations from a global network of Global Navigation Satellite System (GNSS) sites provide information on global mass transport. In this study, we use 19 years of global GNSS station displacements from the 3rd International GNSS Service reprocessing campaign to estimate the coefficients of the spherical harmonics of the Earth’s gravity field up to...