We contribute to the debate on the identification of phase scintillation induced by the ionosphere on the global navigation satellite system (GNSS) by introducing a phase detrending method able to provide realistic values of the phase scintillation index at high latitude. It is based on the fast iterative filtering signal decomposition technique, which is a recently developed fast implementation of

The attitude information of ground vehicles, i.e., heading and pitch information, can be used for many transport applications. This information can be determined through various solutions of onboard sensors, including magnetic sensors, inertial sensors, GNSS equipment, and their combinations. In order to find a cost-effective solution, we propose here a new toolbox named Vehicle Attitude Determination

Zero velocity update technology (ZUPT) has frequently been used as a tool to reduce divergence when the inertial navigation system (INS) is working in pure inertial mode. In general, the normal gravity model is adopted to calculate the gravity vector, and the effect of gravity disturbance is neglected. We present a new point of view to explain the influence of gravity disturbance on INS and point out

Multipath effect is one of the main errors in precise global navigation satellite system (GNSS) positioning. Although there are many GNSS multipath mitigation models available, each model has some limitations. We discuss the problem of mitigating low-frequency multipath in a specific site from the coordinate domain. At present, sidereal filtering is one of the most commonly used methods, in which the

The BDS-3 preliminary system was declared functional on December 27, 2018. It enables positioning service on a global scale. This study conducts a comprehensive investigation of the BDS-3 global service from the perspective of positioning, including satellite ephemeris, benefits of the new BDS-3 satellites, and the new signal effect on three positioning modes: single-point positioning (SPP), precise-point

Carrier phase cycle slips can be an important source of error in precise Global Navigation Satellite System (GNSS) positioning. In such cases, cycle slips can seriously compromise the positioning accuracy and reliability, especially for single-frequency receivers, which do not provide simultaneous measurements at different frequencies to generate effective linear combinations for cycle slip detection

The importance of having high levels of reliability in Global Navigation Satellite Systems (GNSS) signals has increased gradually in recent years. Among other factors, evaluating the available power and its spatial characteristics at the user location is a key task as part of signal quality verification processes. Due to a diversity of factors, the transmitting antennas of GNSS satellites may exhibit

Along with the rapid development of GNSS, not only BeiDou, but also Galileo, and the newly launched GPS satellites can provide signals on three frequencies at present. To fully take advantage of the multi-frequency multi-system GNSS observations on precise point positioning (PPP) technology, this study aims to implement the triple-frequency ambiguity resolution (AR) for GPS, Galileo, and BeiDou-2 combined

The Global Navigation Satellite Systems (GNSS) continuously broadcast radio signals at two or more frequencies in the L-band, providing extensive data for GNSS multipath reflectometry. Multi-GNSS constellations provide more signals and more tracks than individual constellations, achieving greater azimuthal coverage and more frequent retrievals. The main aim of this study is to retrieve snow depth using

A civil navigation signal is vulnerable to interference and tampering owing to its open interface and low signal power. We focus on navigation spoofing. First, using a piecewise function, we quantitatively analyze the effects of the navigation spoofing signal on the receiver tracking loop. For a phase-locked loop, the spoofing signal extends the pull-in range of the discriminator. The autocorrelation

Atmospheric weighted mean temperature, Tm, is a key parameter in ground-based GNSS precipitable water (PW) retrieval, especially for a real-time mode. Considering the seasonal variability of the Tm vertical gradient across the globe, a global grid-based Tm model with seasonal vertical adjustments was developed based on 6-hourly ERA-Interim pressure levels product from European Centre for Medium-Range

The earth rotation parameters (ERPs) are time-variable global geodetic parameters with a purely geophysical origin. Theoretically, the estimates of these parameters should be independent of the satellite constellation used in GNSS processing. Nonetheless, clear differences in the time series of ERPs are noticed when using different GNSS constellations. In this study, GPS, GLONASS, and Galileo estimates

Ionospheric scintillation is a challenging issue for the Global Navigation Satellite System (GNSS). Data collected by the globally distributed GNSS receivers provide abundant information about the ionosphere. S4 is one of the most important parameters of the scintillation, which can be measured by the GNSS receivers. We established a simplified probability model for S4 measured by the GNSS receiver

Autonomous orbit determination (AOD) is the ability of navigation satellites to estimate with accurate satellite orbit parameters using onboard using inter-satellite link (ISL) measurements. To overcome the unobservability of the constellation rotation error in AOD when using only the ISL measurements, the properties that the orbit inclination \( i \) and the longitude of the ascending node \( \varOmega

We developed a global empirical model for computing spherical harmonic (SH) coefficients based on the empirical orthogonal function (EOF) method and periodic functions by utilizing global ionospheric SH coefficients data provided by Center for Orbit Determination in Europe (CODE) during the years 2005–2016. Results show that the first four-order base functions and corresponding associated coefficients

Currently, more than 6000 operating GNSS receivers deliver observations to multiple servers. Ionospheric data are derived from these measurements providing outstanding space coverage and time resolution. There are about 200 million independent measurements daily. Researchers need sophisticated software tools to deal with such a large amount of data. We present recent advances and products from the

Objective The paper aims to present a generalized modulation scheme that can improve the anti-interference performance of global navigation satellite systems (GNSS) and mitigate the ambiguity problem in BOC modulation. Summary background data With the exponential growth of location-based services, there is a need to improve the positioning accuracy and the capability to resist against external interference

Global Navigation Satellite System (GNSS) is now widely used for continuous ionospheric observations. Three-dimensional computerized ionospheric tomography (3DCIT) is an important tool for the reconstruction of electron density distributions in the ionosphere through effective use of the GNSS data. More specifically, the 3DCIT technique is able to resolve the three-dimensional electron density distributions

GPS precise point positioning (PPP) is increasingly being used in many precise positioning applications to achieve sub-meter level accuracy using a stand-alone user receiver. To achieve the full-scale navigation parameters of position, velocity and attitude, GPS is often combined with the inertial navigation system (INS) to deliver navigation solutions in high update rate. However, GPS signals cannot

To meet the demands of research and precise point positioning (PPP) in a multi-GNSS environment, we developed a GNSS data processing software named multi-GNSS automatic precise positioning software (MG-APP). MG-APP is an open-source software that can be run on Windows/Linux/UNIX and other operating systems. It can simultaneously process GPS/GLONASS/BDS/Galileo observations using a Kalman filter or

Using the observations from local and regional GPS networks, the estimation of slant wet delays (SWDs) is possible for each line of sight between satellite and receiver. The observations of SWD are used to model horizontal and vertical variations of the wet refractivity in the atmosphere above the study area. This work is done using the tomography method. In tomography, the horizontal variations of

In 2016, an application programming interface was added to the Android operating systems, which enables the access of GNSS raw observations. Since then, an in-depth evaluation of the performance of smartphone GNSS chips is very much simplified. We analyzed the quality of the GNSS observations, especially the carrier phase observations, of the dual-frequency GNSS chip Kirin 980 built into Huawei P30

We introduce an application framework that enables easy implementation of applications that process GNSS Receiver External Interface Specification (GREIS)-formatted GNSS measurement data. The framework utilizes anti-aging techniques such as automatic code generation, documentation renewal, building, and component testing, which makes this framework effectively an always-up-to-date (“evergreen”) software

A low earth orbit (LEO) constellation can support broadband Internet access and can also be a platform for navigation augmentation for global navigation satellite systems. LEO satellites have the potential to transmit very strong navigation signals; they also show rapid changes in spatial geometry as they come closer to earth and travel faster over stations than satellites in medium or high orbits

In global navigation satellite system (GNSS) meteorology, the weighted mean temperature (Tm) is a variable parameter in the conversion between zenith wet delay errors of GNSS and precipitable water vapor. The combined models of Tm, which are modeled with a combination of Tm seasonal variations and relationships between Tm and site meteorological measurements (mainly site measured temperature), have

Global navigation satellite system (GNSS) positioning in urban areas does not currently provide accurate and stable performance because surrounding buildings can block and reflect satellite signals. However, if we can determine the environment in which the receiver is located, appropriate positioning can be applied. For example, GNSS real-time kinematic and 3D-mapping-aided GNSS (3DMA GNSS) are used

The GNSS tropospheric tomography technique has been proven to be a powerful tool for three-dimensional water vapor reconstruction. In most previous studies, the signals leaving the side face of the tomography area are ignored as having invalid information, which wastes valuable observations and decreases signal coverage of the research area. To include the contribution of such signals to the final

The heavy reliance of real-time precise point positioning (RTPPP) on external satellite clock products may lead to discontinuity or even failure in time-critical applications. We present an alternative approach of real-time undifferenced precise positioning (RUP) that, by combining satellite clock estimation and precise point positioning based on the extended Kalman filter, is independent of external

The differential code bias (DCB) of the global navigation satellite system (GNSS) receiver onboard a low earth orbit (LEO) satellite is one of the crucial hardware error sources in ionospheric estimation. In common practice, LEO DCBs are considered as constant within a single day. However, since such receivers are installed on moving platforms, they are subjected to the ever-changing space environment

We investigate geocenter motion time series derived from the combined solutions and six individual analysis center (AC) solutions of the International GNSS Service (IGS) second reprocessing campaign using the network shift approach, in terms of noise content, long-term trends, periodic and aperiodic variations. We assess these GNSS geocenter motion estimates by comparison with independent estimates

Relative positioning with a moving base is required in many vehicle-to-vehicle applications. Due to unavoidable latency, conventional synchronous real-time kinematic (SRTK) positioning, which refers a fixed base, cannot fulfill the requirements of high-speed safety–critical situations since the movement of the base during the latency must be considered. We present an asynchronous RTK (ARTK)/time-differenced

The International GNSS Service (IGS) Analysis Center Coordinator initiated in 2019 an experimental multi-GNSS orbit combination service by adapting the current combination software that has been used for many years for IGS GPS and GLONASS combinations. The multi-GNSS orbits are based on individual products generated by IGS and multi-GNSS Pilot Project analysis centers. However, the combinations are

As of June 2019, 18 BDS-3 medium earth orbit (MEO) satellites have been launched into orbit. We perform precise orbit determination for these BDS-3 satellites with the rate-limited attitude models and the a priori box-wing solar radiation pressure model. The BDS-3 MEO satellites employ continuous yaw-steering attitude mode. By using proper yaw-attitude models during deep eclipse seasons, the orbit

Snow is an important water resource and plays a critical role in the hydrologic cycle. Accurate measurements of snow depth are needed by scientists to set up a more refined meteorology–hydrology model. Recently, the Global Navigation Satellite System Reflectometry (GNSS-R) has been developed and applied for snow depth monitoring, with low cost and high resolution. We propose an improved snow depth

The total electron content (TEC) is one of the most important parameters for studying the behavior of the ionosphere. The global ionosphere maps (GIMs) can be used to study the TEC time series variations. The time resolution of the GIM-TEC is 2 h, whereas the frequency of the ionospheric temporal behavior can be less than 2 h. To solve this problem, we present a new method for ionosphere time series

Japanese Quasi-Zenith Satellite System (QZSS) consists of three inclined geosynchronous orbit (IGSO) satellites as well as a geostationary satellite. According to the QZSS metadata, the three IGSO satellites are equipped with large L-band antennas, which can be assumed as a combination of a circular cylinder and a circular truncated cone. By using the geometrical and optical properties released by

The Ka inter-satellite link (ISL) has been applied in the new generation of the BeiDou Navigation Satellite System. The next move is to supplement laser ISLs to improve the communication rate and ranging accuracy. A key challenge of the hybrid inter-satellite link network is how to properly schedule the two kinds of inter-satellite links to achieve better system performance, such as robustness, short

Abstract The new FengYun-3 (FY-3) meteorological satellite, FengYun-3D (FY-3D), carries an enhanced version of the GNSS Occultation Sounder (GNOS) instrument with increased BDS and GPS tracking channels. These high-quality onboard BDS observations together with FengYun-3C (FY-3C) data can serve as an effective supplement to overcome the weakness in BDS tracking geometry. To assess the scope of the

Abstract The ground-based augmentation system must make provisions to being sufficiently robustness to ionospheric anomalies through the development of an ionospheric anomaly threat model. For developing the threat model in Brazil, earlier work found that ionospheric spatial decorrelations larger than those in the midlatitude regions were frequently observed during the peak of Solar Cycle #24 (current

Abstract Global pressure and temperature 2 wet (GPT2w) is an empirical model providing the mean values plus annual and semiannual amplitudes of weighted mean temperature (Tm), which makes it a widely used tool in converting zenith wet delay (ZWD) to precipitable water vapor (PWV) in GNSS meteorology. The model meets the needs of real-time Tm anywhere in the world without relying on any other meteorological

Abstract Non-tidal loading (NTL) deforms the earth’s surface, adding variability to the coordinates of geodetic sites. Yet, according to the IERS Conventions, there are no recommended surface-mass change models to account for NTL deformation in geodetic position time series. We investigate the NTL signal recorded at 585 GPS stations at different frequency bands, from day to years, by comparing GPS

Abstract In recent years, the Global Navigation Satellite Systems (GNSS) have been intensively modernized, resulting in the introduction of new carrier frequencies for GPS and GLONASS and the development of new satellite systems such as Galileo and BeiDou (BDS). For this reason, the absolute field antenna calibrations performed so far for the two legacy carrier frequencies, the GPS and GLONASS, seem

Abstract Ephemeris faults must be monitored when integrity is provided for safety–critical applications. The ground facility consisting of multiple short-baseline reference receivers is used to detect the ephemeris faults. The test statistic for the ephemeris fault monitoring is constructed by the double-differenced carrier phase observation. The false alarm and missed detection errors of the proposed

Abstract Cycle slip determination plays an important role in continuous real-time kinematic (RTK) positioning. Since cycle slips should be processed at each epoch, a fast determination method is needed for high-speed RTK applications, such as autopilot and airborne positioning, in which case high-sampling-rate GNSS data (such as 50 HZ) are required to be processed in real time. The geometry-free (GF)

Abstract Since millimeter accuracy is required in many GNSS applications such as real-time zenith wet delay (ZWD) estimation, the higher-order ionospheric delays on GNSS signals are no longer negligible. We calculated the second-order ionospheric delays (\(I_{2}\)) and analyzed the impact on the ZWD estimation with GPS-only and combined GPS/BDS observations. The undifferenced PPP model with fixed coordinates

Abstract GNSSs, such as Galileo and modernized GPS, BeiDou and GLONASS systems, offer new potential and challenges in precise time and frequency transfer using multi-frequency observations. We focus on the performance of Galileo time and frequency transfer using the E1, E5a, E5b and E5 observations. Dual-frequency, triple-frequency and quad-frequency models for precise time and frequency transfer with

Abstract Array signal processing is attractive for Global Navigation Satellite System (GNSS) applications, as the desired reception environments for GNSS are becoming more challenging, while users’ demands for high-accuracy positioning are growing. One goal of array signal processing is to find the direction of arrival (DOA) of the signal source. Several advanced techniques have been proposed to estimate

Abstract The Chinese BeiDou Navigation Satellite System (BDS) transited from regional (Asia–Pacific) to global on December 28, 2018. In this study, the performance of PPP-RTK based on BDS-3/BDS-2/GPS observations is analyzed by utilizing the observations in Europe during a calm ionospheric disturbance period with Kp-index ranging from 0o to 2-. Satellite clock offsets are first estimated and then fixed

Abstract Currently, many commercial airline aircraft cannot perform three-dimensionally guided approaches based on satellite-based augmentation systems. We propose a system to rebroadcast the correction and integrity data via a data link as provided by the ground-based augmentation system such that aircraft equipped with a GPS landing system (GLS) can use the wide-area corrections and perform localizer

Abstract The combined navigation system consisting of Global Positioning System (GPS) and Inertial Navigation System in a complementary mode assures an accurate, reliable, and continuous positioning capability in the navigation system. Because of problems such as dealing with a low-cost MEMS-based inertial sensors having a high level of uncertainty and imprecision, stochastic noise, a high-speed vehicle

Abstract The satellite clocks of the BeiDou Navigation Satellite System (BDS) have characteristic differences compared to those of the global positioning system and Galileo. Therefore, the satellite clock offsets prediction method of BDS is different from those of these two systems. The basis for establishing a more appropriate prediction model is to clarify the statistical characteristics of the BDS

Abstract Both the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archival Center (CDAAC) and the European Radio Occultation Meteorology Satellite Application Facility (ROM) process the radio occultation data from the Global Navigation Satellite System Receiver for Atmospheric Sounding (GRAS) onboard the MetOp-A/-B satellites. CDAAC- and ROM-processed