Search

Real-time monitoring of earthquake-triggered surface deformation is becoming required to characterize the effect of an earthquake, either transient or permanent deformation. Indonesia as a country located in the active deformation region, through Geospatial Information Agency (BIG) has built 397 Real-Time Global Navigation Satellite Systems (RT-GNSS) stations that can be used to observe this phenomenon. The availability of RT-GNSS stations motivates us to provide real-time surface deformation information using the appropriate RT-GNSS processing method. We implement Precise Point Positioning with Regional Augmentation correction (PPP-RA) for stations if there are sufficient regional corrections, and Precise Point Positioning with Ambiguity Resolution (PPP-AR) otherwise. The result shows from Kota Fajar station in Sumatera Island (CKTF), the accuracy can be achieved at ± 1.4 cm, ± 1.8 cm, and ± 6.5 cm for the North, East, and Up components, respectively. we use the earthquake location information produced by Indonesia Tsunami Early Warning System (InaTEWS) operated by the Meteorological, Climatological, and Geophysical Agency (BMKG) to automatically collect the nearby stations from the epicenter. Then, we compute the displacement from each of its stations every second when the earthquake occurred. As a result, we can detect the transient deformation of the Banda Sea earthquake 7.6 Mw at depth of 108 km on January 9, 2023, with a maximum dynamic displacement at the nearest station to the source is 6.6 cm in the North-South direction and 8.7 cm in the East-West direction. This result suggests that this system is effective in displacement detection due to earthquakes., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Real-time Global Navigation Satellite Systems (GNSS) are critical for precise and reliable positioning, navigation, and timing (PNT) services, including both civil applications with an accuracy of meter-level and geohazard early warning systems with an accuracy of cm- or even mm-level. For high-precision real-time GNSS applications, the precise orbits, clocks, hardware delays, and atmospheric information are estimated and disseminated in real time by the service provider. In this study, we introduce the current status and recent developments of the GFZ GNSS real-time analysis center. We introduce the data processing strategy for generating satellite orbits and clocks, hardware delays, and atmospheric information, and present the accuracy of the online operational products. We focus on the recent developments in improving the accuracy and reducing the latency of real-time products, such as shortening the ultra-rapid orbit processing time and improving the predicting accuracy, estimating orbits with real-time streaming data, and adopting the un-differenced ambiguity resolution in the estimation of real-time clocks and orbits. Lastly, we evaluate the real-time positioning performance using the GFZ real-time products, and demonstrate with the atmospheric augmentation information, the cm-level accuracy can be achieved within a few minutes., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

For microwave-based space geodetic techniques, co-located instruments within a few hundred meters are considered to share the same troposphere, and thus intra-/inter-technique tropospheric ties can be applied to improve the multi-technique integrated solution. The concept of applying tropospheric ties assumes that tropospheric parameters from each technique represent the true tropospheric state, i.e., (1) there should be no technique-related systematic bias, and (2) the technique-specific stochastic noise that leaks into atmospheric delay estimates should be minimized. However, this is usually not the case in reality, as the modeling and parameter estimation in the analysis of space geodetic techniques naturally contain systematic and stochastic uncertainty. For example, the multi-path effect and antenna phase center variation (PCV) error could introduce systematic biases in Global Navigation Satellite Systems (GNSS) tropospheric parameters, and the limitation of observation geometry in Very Long Baseline Interferometry (VLBI) could bias the horizontal gradients. Therefore, it is critical to identify and handle the systematic biases, and properly handle the stochastic part. In this study, we demonstrate that tropospheric parameter biases could be large, e.g., up to 5 mm in zenith total delay (ZTD). Ignoring systematic biases distorts the ground network, especially the VLBI network. For example, the systematic bias in ZTD shifts the network scale, and the bias in horizontal gradients rotates the network and deteriorates earth orientation parameters (EOP). We demonstrate that the GNSS and VLBI integrated solution can be improved after properly handling the tropospheric ties., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Accurate tropospheric delays from Numerical Weather Models (NWM) are an important input to space geodetic techniques, especially for precise real‐time Global Navigation Satellite Systems, which are indispensable to earthquake and tsunami early warning systems as well as weather forecasting. The NWM‐based tropospheric delays are currently provided either site‐specific with a limited spatial coverage, or on two‐dimensional grids close to the Earth surface, which cannot be used for high altitudes. We introduce a new method of representing NWM‐derived tropospheric zenith hydrostatic and wet delays. A large volume of NWM‐derived data is parameterized with surface values and additional two or three coefficients for their vertical scaling to heights up to 14 km. A precision of 1–2 mm is achieved for reconstructing delays to the NWM‐determined delays at any altitudes. The method can efficiently deliver NWM‐derived tropospheric delays to a broader community of space geodetic techniques., Plain Language Summary: Precise positioning with microwave‐based space geodetic techniques, such as Global Navigation Satellite Systems (GNSS), requires accurate modeling of the atmospheric refraction. Numerical Weather Models (NWM) can provide tropospheric delays with an accuracy of 1–2 cm in zenith direction and are therefore useful for improving the data analysis. However, due to the large data volume to handle, NWM‐based products are typically provided only for selected sites, or on a global grid referring to a specific height. We provide an efficient method to represent the vertical profile of tropospheric delay from the Earth surface up to 14 km altitude with a precision of 1–2 mm. The method is used to preserve the precision of NWM‐derived tropospheric delays at the altitudes using three to four coefficients per geographic location (longitude, latitude) at the ground. This paves the way of applying the NWM‐based accurate tropospheric delays in space geodetic data analysis, especially for global augmentations of real‐time GNSS, which play a critical role in the rapid characterization and early warning of geohazards such as earthquake and tsunami, as well as kinematic platforms of high altitudes., Key Points: New method for precise modeling of the zenith hydrostatic and wet delays from the Earth surface up to an altitude of 14 km. Tropospheric delay vertical modeling precision of better than 3 mm is achieved on a global scale. The method provides numerical weather model‐derived precise tropospheric augmentation correction for real‐time space geodetic techniques., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659, China Scholarship Council CSC, Helmholtz OCPC Program, https://cds.climate.copernicus.eu/cdsapp

The orbit accuracy of the navigation satellites relies on the accurate knowledge of the forces on the spacecraft, in particular the non-conservative perturbations. This study focuses on the Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites of the regional Chinese BeiDou Navigation Satellite System (BDS-2), for which apparent deficiencies of non-conservative models are identified and evidenced in the Satellite Laser Ranging (SLR) residuals. The orbit errors derived from the empirical 5-parameter Extended CODE Orbit Model (ECOM) as well as a semi-analytical adjustable box-wing model show prominent dependency on the Sun elongation angle, even in the yaw-steering attitude mode. Hence, a periodic acceleration in the normal direction of the +X surface, presumably generated by the mismodeled thermal radiation pressure, is introduced. The SLR validations reveal that the Sun elongation angle-dependent systematic errors were significantly reduced, and the orbit accuracy was improved by 10–30% to approximately 4.5 cm and 3.0 cm for the BDS-2 IGSO and MEO satellites, respectively.

Wide-lane (WL) uncalibrated phase delay (UPD) is usually derived from Melbourne–Wübbena (MW) linear combination and is a prerequisite in Global Navigation Satellite Systems (GNSS) precise point positioning (PPP) ambiguity resolution (AR). MW is a linear combination of pseudorange and phase, and the accuracy is limited by the larger pseudorange noise which is about one hundred times of the carrier phase noise. However, there exist inconsistent pseudorange biases which may have detrimental effect on the WL UPD estimation, and further degrade user-side ambiguity fixing. Currently, only the large part of pseudorange biases, e.g., the differential code bias (DCB), are available and corrected in PPP-AR, while the receiver-type-dependent biases have not yet been considered. Ignoring such kind of bias, which could be up to 20 cm, will cause the ambiguity fixing failure, or even worse, the incorrect ambiguity fixing. In this study, we demonstrate the receiver-type-dependent WL UPD biases and investigate their temporal and spatial stability, and further propose the method to precisely estimate these biases and apply the corrections to improve the user-side PPP-AR. Using a large data set of 1560 GNSS stations during a 30-day period, we demonstrate that the WL UPD deviations among different types of receivers can reach ± 0.3 cycles. It is also shown that such kind of deviations can be calibrated with a precision of about 0.03 cycles for all Global Positioning System (GPS) satellites. On the user side, ignoring the receiver-dependent UPD deviation can cause significant positioning error up to 10 cm. By correcting the deviations, the positioning performance can be improved by up to 50%, and the fixing rate can also be improved by 10%. This study demonstrates that for the precise and reliable PPP-AR, the receiver-dependent UPD deviations cannot be ignored and have to be handled., China Scholarship Council http://dx.doi.org/10.13039/501100004543, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ (4217), ftp://geodesy.noaa.gov/cors/rinex/, ftp://ftp.gfz-potsdam.de/GNSS/products/mgex/, ftp://ftp.aiub.unibe.ch/CODE/

Comunicación expuesta online en el CYGNSS Science Team Summer Meeting celebrado del 27 al 29 de julio de 2021

BeiDou navigation satellite system is currently the only system which the whole constellation offers triple-frequency observation data, triple-frequency observation is conducive to carrier phase ambiguity fixing quickly and accurately. The algorithm of triple-frequency integer ambiguity resolution between BDS network RTK reference stations is proposed. The observation of B2 frequency and B3 frequency and the strict criterion of ambiguity fixing are used to determine extra-wide-lane integer ambiguity. The linear relationship between fixed extra-wide-lane integer ambiguity and other wide-lane integer ambiguity is selected as constraint conditions, then the wide-lane integer ambiguity, relative zenith tropospheric delay error and ionospheric delay error are estimated and the wide-lane integer ambiguity can be fixed by search mode. There is a kind of integer linear relationship between fixed wide-lane integer ambiguity and triple-frequency carrier phase integer ambiguity, this linear relationship is added to the observation model of carrier phase ambiguity parameter estimation and the integer ambiguity can be fixed. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results indicate that triple-frequency carrier phase ambiguity can be fixed accurately and effectively with the method.

System Erde; 8, Geodesy aims to determine the geometric figure and the gravitational field of the Earth, as well as its orientation in space. Steadily increasing accuracies, with which these tasks are being solved, are based on corresponding improvements in geodetic measuring data, both, on the quantitative as well as the qualitative level. Similar developments in the acquisition, processing and analysis of observation data, which have always been at the limit of the technically and scientifically feasible, are witnessed in the fields of seismology and geomagnetism as well. Recently however, innovative developments, building on Big Data approaches, are emerging with the combination of diverse data streams into integrated processing environments. Geodetic, seismological and geomagnetic observation data are fundamental for a better understanding of Earth system processes. The combination of these geoscience data collected by ground- and space-based sensors, their consistent processing, validation and assimilation into complex Earth system models contribute in an essential way to the future implementation of GGOS, the Global Geodetic Observing System.