Abstract 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”)

Abstract 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

Abstract 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)

Abstract 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)

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

Abstract 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

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