In 2020, the BeiDou navigation satellite system (BDS) initiated a real-time service (RTS) for precise point positioning (PPP) using the B2b signal for users in China and its surrounding areas. A decimeter-level accuracy is expected to be achieved using a single receiver. In this study, the PPP-B2b service is experimentally analyzed based on 7 days of corrections and compared with the RTS provided by

By minimizing the mean squared error, Kalman filter provides optimal estimates with exact system models and precise statistical information of the noises, and the filter may fail or be affected seriously with uncertain models and noises. In the dynamic positioning and navigation field, the filter with the adaptive factor or the fading factor was developed to overcome the drawbacks of the Kalman filter

Low earth orbit (LEO) satellite constellations have the potential to augment global navigation satellite system services. Among the ongoing tasks of LEO-based navigation, providing broadcast ephemerides that satisfy the accuracy requirement for positioning, navigation, and timing is one of the most critical prerequisites. Singularities can occur when fitting broadcast ephemeris parameters in the case

To resolve undifferenced GNSS phase ambiguities, dedicated satellite products are needed, such as satellite orbits, clock offsets and biases. The International GNSS Service CNES/CLS analysis center provides satellite (HMW) Hatch-Melbourne-Wübbena bias and dedicated satellite clock products (including satellite phase bias), while the CODE analysis center provides satellite OSB (observable-specific-bias)

Global Navigation Satellite System interferometric reflectometry (GNSS-IR) can be used to monitor a series of geophysical parameters in a cost-effective manner with high temporal resolution. The technique makes use of the simultaneous reception of direct and reflected GNSS signals with a single antenna. Based on the low-cost u-blox M8N chips, a GNSS-IR instrument is developed, which could be used to

Usually, the difference between the satellite clocks computed with L1/L2 and clocks computed with L1/L5 is defined as inter-frequency clock bias (IFCB). It is critical to correct its L5 time-variant portion in the GNSS triple-frequency precise positioning. Using two years of observations from more than 100 stations worldwide, we use the epoch-differenced method to estimate IFCB for all available 12

Extreme Energy Events (EEE) is an extended Cosmic Rays (CRs) Observatory, composed of about 60 tracking telescopes spread over more than 10 degrees in Latitude and Longitude. We present the metrological characterization of a representative set of actually installed EEE GPS receivers, their calibration and their comparison with respect to dual-frequency receivers for timing applications, as well as

Multipath is one of the major error sources in high-precision GNSS positioning since it cannot be mitigated by double differences or corrected by empirical models. Considering that the multipath error is related to the carrier-to-noise ratio (CNR) of the signal strength, an enhanced multipath extraction and mitigation method based on an adaptive layer wavelet packets, bootstrapped searches strategy

When plasma instabilities arise in the post-sunset time, the so-called ionospheric plasma bubbles may develop, causing amplitude fades and phase oscillations, decreasing the availability and quality of transionospheric communication systems. In the regions where these bubbles appear, deep signal fading may occasionally reach the lowest levels and with loss of signal received for a certain period. In

To further enhance the positioning accuracy and stability of the INS/GNSS integrated navigation system, we present a new fuzzy strong tracking cubature Kalman filter (FSTCKF) algorithm for data fusion. A fuzzy logic controller is designed for the strong tracking cubature Kalman filter (STCKF), which aims at strengthening the filter’s ability to identify and respond to the dynamics. Chi-square tests

We propose a new method for spatio-temporal modeling of the ionospheric total electron content (TEC) at severe solar activity periods using a support vector machine (SVM). Using the observations from 37 GPS stations of the Iranian permanent GPS network (IPGN) in 2013–2014, the new model has been evaluated. Observations of 33 stations are used for training. Also, four stations are selected to test and

The multipath effect reduces the accuracy of pseudorange and carrier phase observations and significantly affects the convergence of precise point positioning (PPP) in an urban high-obstruction environment. The multipath hemispherical map (MHM) is based on the spatial repeatability of the multipath and is used to mitigate the multipath effect. This method is widely used because it is suitable for real-time

Atmospheric pressure is a widely used meteorological parameter, and surface pressure at antenna height is one of the most important parameters for calculating the Global Navigation Satellite System (GNSS) tropospheric hydrostatic delay. The latter is responsible for about 90% of the total tropospheric delay, which is one of the main error sources in geodetic applications. For convenience, a standard

Benefiting from the special design of BeiDou Navigation Satellite System (BDS) constellation, its Geostationary Earth Orbit (GEO) satellites observations can provide favorable conditions to investigate the ionospheric plasma bubble at low latitudes. This study proposes using BDS GEO Rate of Total Electron Content Index observations to analyze the equatorial plasma bubble characteristics. We use GEO

The low-cost receiver with multi-frequency and multi-constellation Global Navigation Satellite System (GNSS) observations is becoming the mainstream in positioning and navigation. It is crucial to estimate systematic errors, including the multipath, differential code bias (DCB), and inter-system bias (ISB) for such receivers. The traditional analysis strategies are based on the geometry-free and ionospheric-free

A challenging and outstanding problem in applications that involve or rely on GPS signals is to mitigate jamming. We develop a machine learning-based antijamming framework for GPS signals. Three types of jamming signals are considered: continuous wave interference, chirp and pulse jamming. In addition, white Gaussian noise is assumed to be present. From the point of view of communication, information

A correction to this paper has been published: https://doi.org/10.1007/s10291-021-01146-7

It is foreseeable that the BeiDou navigation satellite system with global coverage (BDS-3) and the BeiDou navigation satellite (regional) system (BDS-2) will coexist in the next decade. Care should be taken to minimize the adverse impact of the receiver-related biases, including inter-system biases (ISBs), differential code biases (DCB), and differential phase biases (DPB) on the positioning, navigation

The BeiDou Navigation Satellite System (BDS) is experiencing a transition from regional (BDS-2) to global (BDS-3) service capability, and both BDS-2 and BDS-3 jointly provide primary navigation services. Using approximately 5-years of ephemerides since January 2016 from the International Global Navigation Satellite Systems (GNSS) Service (IGS) and precise products from Wuhan University (WHU), we provide

The distribution of clock correction and ephemeris (CCE) parameters in navigation messages broadcast by operational satellite vehicles (SVs) of the Global Navigation Satellite System (GNSS) is studied. For this purpose, two evaluation metrics are proposed, namely atypical navigation message structures and time to complete CCE sets (TTCS). The evaluation metrics are used to analyze three and a half

GNSS satellite and receiving antennas exhibit group delay variations (GDV), which affect code pseudorange measurements. Like antenna phase center variations, which affect phase measurements, they are frequency-dependent and vary with the direction of the transmitted and received signal. GNSS code observations contain the combined contributions of satellite and receiver antennas. If absolute GDV are

The multipath effect inhibits the centimeter-accuracy positioning in Android smart devices which have poor multipath suppression. We investigate the multipath extraction effectiveness in the reduction of the noise of low-accuracy positioning devices. Considering the multipath error frequency characteristics, we combine the wavelet-based method and empirical mode decomposition (EMD) to reduce the noise

The tropospheric delay is an important error source in the Global Positioning System (GPS) positioning and navigation applications. Although most of the tropospheric delays can be removed in the double-differencing (DD) positioning mode, their remaining residuals can still contaminate the positioning accuracy and become unpredictable when tropospheric condition encounters severe variations such as

With the development of GNSS, many open-source software packages have become available for GNSS data processing. However, there are only a handful of open-source software that can handle GNSS/INS integrated data, even though GNSS/INS integration schemes have been widely used in vehicle navigation systems due to their high accuracy, stability, and continuity in harsh environments. Considering the above

Precise point positioning (PPP) can be significantly improved with the multi- multi-GNSS constellation, but it still takes more than 10 min to obtain positioning results at centimeter-level accuracy. We develop a multi-constellation (GPS + GLONASS + Galileo + BDS) PPP ambiguity resolution (AR) method augmented by precise atmospheric corrections to achieve instantaneous centimeter-level positioning

We report the GPS satellite clock estimation using 20 globally distributed receivers with an external hydrogen maser atomic clock. By applying corrections for the Sagnac effect, the relativistic effect due to orbit eccentricity, tropospheric and ionospheric delays, satellite and receiver antenna phase center offsets and variations, solid earth tides, ocean tide loading, phase wind-up effect, and P1-C1

We describe our investigation into the performance of low-power heterogeneous timing systems for small satellites, using real GPS observables from the GRACE Follow-On mission. Small satellites have become capable platforms for a wide range of commercial, scientific and defense missions, but they are still unable to meet the needs of missions that require precise timing, on the order of a few nanoseconds

A correction to this paper has been published: https://doi.org/10.1007/s10291-021-01141-y

Ionosphere Associate Analysis Centers (IAACs) of the International GNSS Service (IGS) independently produce global ionosphere maps (GIMs) of the total electron content (TEC). The GIMs are based on different modeling techniques, resulting in different TEC levels and accuracies. In this study, we evaluated the accuracy and consistency of the IAAC GIMs during high (2014) and low (2018) solar activity

Integer ambiguity resolution is the key for achieving the highest accuracy with Precise Point Positioning (PPP) and for significantly reducing the convergence time. Unfortunately, due to hardware phase biases originating from the satellites and receiver, fixing the phase ambiguities to their correct integer number is difficult in PPP. Nowadays, various institutions and analysis centers of the International

Spurious draconitic errors with periods of (351.4/N) days are detected in GPS position time series. This study assesses the performance of ambiguity resolution in sub-daily position estimates on reducing the draconitic errors. Precise point positioning solutions covering 132 global stations from 2002 to 2017 are generated with and without ambiguity resolution using 24-, 8- and 4-h processing sessions

The proper handling of code biases is essential for realizing precise ionospheric modeling, positioning and timing. It is common to treat code biases in a differential mode as a differential code bias (DCB). With the modernization of GPS and GLONASS and the implementation of Galileo and BDS, the traditional DCB calibrations are complex and not easily extendable to different frequencies and modulations

A precise Global Navigation Satellite System (GNSS) satellite orbit is an essential prerequisite for precise point positioning (PPP). Due to the daily orbit discontinuities (DODs) between adjacent daily orbit products provided by the International GNSS Service, the interpolation accuracy at the epochs near the day boundaries cannot be as high as expected and can significantly degrade the positioning

Reanalysis products have been applied to calculate the tropospheric delay for Global Navigation Satellite System (GNSS) positioning purposes widely. It is necessary to obtain high-precision tropospheric delay information from GNSS users with a high-precision tropospheric vertical stratification model because the height of the grids of the atmospheric reanalysis data is inconsistent with that of GNSS

The BeiDou-3 system uses the BeiDou Global broadcast Ionospheric delay correction Model (BDGIM) to describe global vertical total electron content (VTEC) distributions and provide ionospheric delay mitigations in single-frequency positioning. The transmission of BDGIM correction parameters in the navigation message of BeiDou-3 started in mid-2015. The limited coverage of BeiDou-3 transmitted BDGIM

An assessment of standalone GLONASS RTK performance is provided using its FDMA and CDMA signals. The new integer-estimable GLONASS FDMA model (Teunissen 2019), which guarantees the integer-estimability of its ambiguities, is employed. We introduce the combined integer-estimable GLONASS FDMA+CDMA model and compare its strength against the FDMA model for instantaneous integer ambiguity resolution and

Compared to the BeiDou regional navigation satellite system (BDS-2), the BeiDou global navigation satellite system (BDS-3) includes the newly designed B1C and B2a signals, which are compatible with the L1 and L5 frequencies of the global positioning system (GPS). Considering that the precise orbit determination (POD) of the BDS-3 constellation is currently restricted to the legacy B1I and B3I signals

We present the results of 10 years of research related to the development of a Rubidium vapor cell clock based on the principle of pulsed optical pumping (POP). Since in the pulsed approach, the clock operation phases take place at different times, this technique demonstrated to be very effective in curing several issues affecting traditional Rb clocks working in a continuous regime, like light shift

A near-real-time computerized ionospheric tomography (CIT) technique was developed over the East Asian sector to specify the 3-D electron density field. The technique is based on a plethora of Global Navigation Satellite System observables within the region of interest which is bounded horizontally 110°–160°E and 10°–60°N and extending from 80 to 25,000 km in altitude. Prior to deployment, studies

In the high orbit space, the visibility of GPS main lobe signal is poor due to the earth's occlusion and the increase in signal transmission distance. Therefore, the side lobe signals are essential for navigation mission, which puts forward higher requirements for the sensitivity of the receiver. In addition, the cross-correlation interference (CCI) caused by the large power difference between the

Micro-electro-mechanical system (MEMS)-based inertial measurement unit (IMU) together with single-frequency Global Navigation Satellite System (GNSS) receiver provides a cost-efficient solution for outdoor navigation. An accurate initial alignment is necessary to the GNSS/IMU integrated navigation system to guarantee a good performance. Existing in-motion alignment methods mostly rely on the velocity

We examine the sensitivity of the Global Positioning System (GPS) to non-tidal loading for a set of continental Eurasia permanent stations. We utilized daily vertical displacements available from the Nevada Geodetic Laboratory (NGL) at stations located at least 100 km away from the coast. Loading-induced predictions of displacements of earth’s crust are provided by the Earth-System-Modeling Group of

Due to poor local accuracy and temporal resolution, the GIM (global ionospheric map) application continues to be of restricted use in obtaining the characteristics of seismic-ionospheric effects. Utilizing spherical harmonic (SH) function and generalized trigonometric series (GTS), the latest 15 min/map GIM with high precision released from the Chinese Academy of Sciences (CAS), is expected to record

With the widespread application of global navigation satellite system, increasing amounts of gridded tropospheric data have been generated, increasing the difficulty of real-time transmission. We present that the global tropospheric grid data (GTGD) provided by Vienna mapping functions open access data have approximate sparse characteristics, and the compressed sensing (CS) method is used for sparse

With the rapid development of Global Navigation Satellite Systems (GNSS), precise point positioning (PPP) has been widely used for positioning, navigation, timing (PNT), and atmospheric sensing. Currently, the demand for low-cost single-frequency hardware is increasing. However, open-source single-frequency PPP (SFPPP) software, in particular those that employ uncombined GNSS observations, is scarce

Change detection within unequally spaced and non-stationary time series is crucial in various applications, such as environmental monitoring and satellite navigation. The jumps upon spectrum and trend (JUST) is developed to detect potential jumps within the trend component of time series segments. JUST can simultaneously estimate the trend and seasonal components of any equally or unequally spaced

Accurate timing is one of the key features of the Global Positioning System (GPS), which is employed in many critical infrastructures. Any imprecise time measurement in GPS-based structures, such as smart power grids, economic activities, and communication towers, can lead to disastrous results. The vulnerability of the stationary GPS receivers to the time synchronization attacks (TSAs) jeopardizes

Future generations of global navigation satellite systems (GNSSs) can benefit from optical technologies. Especially optical clocks could back-up or replace the currently used microwave clocks, having the potential to improve GNSS position determination enabled by their lower frequency instabilities. Furthermore, optical clock technologies—in combination with optical inter-satellite links—enable new

With the development of high-precision safety–critical applications using global navigation satellite systems (GNSS), fault detection and exclusion (FDE) is indispensable to guaranteeing the integrity of a GNSS positioning and navigation system. Many FDE algorithms have been developed based on the standard Kalman filter (KF), assuming that GNSS measurements come with Gaussian uncorrelated white noise

GNSS observation outage occurs inevitably in various situations, e.g., automobile driving in urban environments. Although the ambiguity resolution (AR) significantly shortens the initialization time of precise point positioning (PPP), frequent re-initialization of PPP AR may be needed due to outages. The inertial navigation system (INS) can be used for acquiring highly accurate position information

In a satellite navigation system, high-precision prediction of satellite clock bias directly determines the accuracy of navigation, positioning, and time synchronization and is the key to realizing autonomous navigation. To further improve satellite clock bias prediction accuracy, we establish a satellite clock bias prediction model by using long short-term memory (LSTM) that can accurately express

Global Navigation Satellite System (GNSS) tomography has proved its potential for sensing the three-dimensional (3D) distribution of atmospheric water vapor. Although the standard tomography model has improved, the geometry defect of GNSS acquisition remains a key problem and thus becomes the focus of this research. Thanks to the availability of high-resolution Moderate Resolution Imaging Spectroradiometer

For more than 20 years, precise point positioning (PPP) has been a well-established technique for carrier phase-based navigation. Traditionally, it relies on precise orbit and clock products to achieve accuracies in the order of centimeters. With the modernization of legacy GNSS constellations and the introduction of new systems such as Galileo, a continued reduction in the signal-in-space range error

Global navigation satellite systems (GNSSs) usually adopt constant-envelope multiplexing (CEM) techniques to deal with the nonlinear characteristic of high-power amplifiers (HPAs) on satellites. However, almost all the existing navigation signal CEM techniques assume that the bandwidth of the transmitter is large enough when compared to that of navigation signals, which often contradicts reality, especially

We have reconstructed integrated water vapor (IWV) using the zenith wet delays to track the properties of hurricanes and explore their spatial and temporal distributions estimated from 922 GPS stations. Our results show that a surge in GPS-derived IWV occurred at least six hours prior to the landfall of two major hurricanes (Harvey and Irma) that struck the Gulf and East Coasts of the USA in 2017.

A test campaign for carrier phase timing was conducted on the BDS/GNSS Open Testing Platform (BOTP), which was established by the National Time Service Center, Chinese Academy of Sciences (NTSC, CAS), using communication satellites in geosynchronous orbit. Its purpose was a navigation technology experiment and verification platform for BDS and GNSS. The system architecture of BOTP, a novel navigation

Monitoring sea level is critical due to climate change observed over the years. Global Navigation Satellite System Reflectometry (GNSS-R) has been widely demonstrated for coastal sea-level monitoring. The use of signal-to-noise ratio (SNR) observations from ground-based stations has been especially productive for altimetry applications. SNR records an interference pattern whose oscillation frequency

Non-line-of-sight (NLOS) global navigation satellite system (GNSS) signals are a major factor that limits the GNSS positioning accuracy in urban areas. An advanced GNSS signal processing technique, the vector tracking loop (VTL), has been applied to NLOS detection and correction, and its feasibility and superior performance have been reported in recent studies. In a VTL-based GNSS receiver, the navigation

The differential code biases (DCBs) of the global positioning system (GPS) receiver onboard low-Earth orbit (LEO) satellites are commonly estimated by a local spherical symmetry assumption together with the known GPS satellite DCBs from ground-based observations. Nowadays, more and more LEO satellites are equipped with GPS receivers for precise orbit determination, which provides a unique chance to

Gravity fields derived from GPS tracking of the three Swarm satellites have shown artifacts near the geomagnetic equator, where the carrier phase tracking on the L2 frequency is unable to follow rapid ionospheric path delay changes due to a limited tracking loop bandwidth of only 0.25 Hz in the early years of the mission. Based on the knowledge of the loop filter design, an analytical approach is developed