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GNSS precise point positioning (PPP) plays an important role in retrieving atmospheric water vapor values and performing numerical weather prediction. However, traditional PPP relies on real-time orbits and clocks, which require continuous internet or satellite communication. Improved broadcast ephemerides of GNSSs offer new opportunities for PPP with broadcast ephemerides (BE-PPP) instead of using precise ephemeride products. Therefore, we investigated the feasibility of utilizing BE-PPP for retrieving zenith tropospheric delay (ZTD) and precipitable water vapor (PWV) data. We processed the GPS/Galileo observations from 80 IGS stations during a 30-day experiment to retrieve ZTD values using both real-time PPP (RT-PPP) and BE-PPP solutions. Then, we processed observations from 20 EUREF Permanent GNSS Network (EPN) stations to retrieve PWV data. The IGS final tropospheric products were used to validate the ZTD, and radiosonde (RDS) and ERA5 data were used to validate the PWV. The results show that the real-time ZTD from BE-PPP agrees well with that from RT-PPP: the standard deviation (STD) of the ZTD is 1.07 cm when using BE-PPP and 0.6 cm when using RT-PPP. Furthermore, the STD of the PWV is 1.69 mm when using BE-PPP, and 0.96 mm when using RT-PPP, compared to the ERA5-PWV. Compared to the RDS-PWV, the STD is 3.09 mm when using BE-PPP and 1.39 mm when using RT-PPP. In conclusion, the real-time ZTD/PWV products obtained using the BE-PPP solution are consistent with those of RT-PPP and meet the requirements of NWP, so this method can be used as an effective complement to RT-PPP to expand its application potential.

The neritic region of the Chaoshan plain is located on the northeastern (NE) boundary of the South China Sea (SCS). Despite the extensive research on the stratigraphic architecture and sedimentary processes within the Chaoshan plain, the neighboring neritic area remains largely unexplored. In this study, we provide a new set of ages on seventeen quartz optically stimulated luminescence (OSL) dating results from four cores (SY2-2, SY3-1, SY3-2, and HS02) to investigate the regional chronostratigraphy and sedimentology of the area. The samples were collected at depths ranging from 0.6 to 73.5 m and yielded ages ranging from 4.9 ± 0.3 ka to >139 ± 28 ka. Sedimentation thickness from cores SY3-2, SY2-2, and HS02 is less than 4.2 m, 5.5 m, and 6.4 m, respectively, since at least Marine Isotope Stage (MIS) 5, and the Holocene sediments of core SY3-2 are less than 4.2 m thick. The preservation state of the sediments in the area is poor since at least 83.6 ka, indicating an intensified erosion in the neritic region of the northeastern South China Sea (NESCS) since at least MIS 5. This erosion may have been caused by fluvial incision resulting from sea-level decline during the last glacial period, as well as strong transportation caused by coastal currents.

Abstract China Geodetic Coordinate System 2000 (CGCS2000), as the formal national coordinate reference frame, has been used for 20 years. The coordinates of all Global Navigation Satellite System (GNSS) stations in China need referring to this system. To this end, the first step is to align the coordinates of all stations, usually included in a regional GNSS network, with a given International Terrestrial Reference Frame (ITRF), then these coordinates are corrected to the CGCS2000 in consideration of plate movement. For a better alignment result, regional control stations are needed and their coordinates were estimated from the combination of constraint-free normal equation systems provided by several International GNSS Service (IGS) analysis centers. The effect in using these refined coordinates, which determine a regional coordinate datum, on the alignment result should be evaluated by the coordinate corrections of the regional control stations to the regional coordinate datum, i.e. smaller corrections mean better alignments of the two associated frames. The test results show that the refined coordinates are more accurate than the ones calculated from the station's velocity, and are well aligned with the ITRF2005. Moreover, for obtaining the coordinates of GNSS stations in an updated CGCS2000 frame, a gridded linear velocity field based on the estimated velocities at 1025 CGCS2000 stations was generated for mainland China using the optimal interpolation method, the inverse distance weighting, which is selected from five interpolation methods. The overall precisions of the constructed velocity field at all stations in the East (E) and, North (N) directions are 0.78 mm/a and 0.95 mm/a, respectively. For evaluating the accuracy of the updated CGCS2000 frame, monthly solutions for the coordinates of some CGCS2000 CORS stations in the ITRF2014 during the period from 2000.0 to 2018 were obtained and the Root Mean Square (RMS) of the differences between the coordinates corrected to the CGCS2000 and the known coordinates at these stations are about 2–3 cm.

China Geodetic Coordinate System 2000 (CGCS2000) has been used for several years as a formal published reference frame. The coordinates of all global navigation satellite system (GNSS) stations in China need to be corrected to align with the CGCS2000 frame. Different strategies can be adopted for the realization of an optimal reference frame. However, different strategies lead to different results, with differences as great as several decimeters when GNSS station coordinates are transformed into CGCS2000-defined coordinates. The two common methods for the coordinate correction of a GNSS station are quasi-stable adjustment under CGCS2000 and plate movement correction, and the differences between their results can be greater than 10 cm. In this study, a statistic method called “supervised clustering” is applied to the selection of GNSS reference stations; a new scheme named “partition spacing” for the grouping of all processed GNSS stations is proposed; and the plate movement correction method is used to correct the coordinates of all GNSS stations from the GNSS epoch to the CGCS2000 epoch. The results from the new partitioning method were found to be significantly better than those from the conventional station-blocking approach. When coordinates from the stations without grouping were used as the standard, the accuracy of all the three-dimensional coordinate components from the new partitioning method was better than 2 mm. The root mean squares (RMSs) of the velocities in the x, y, and z directions resulting from the supervised clustering method were 0.19, 0.45, and 0.32 mm∙a−1, respectively, which were much smaller than the values of 0.92, 0.72, and 0.97 mm∙a−1 that resulted from the conventional approach. In addition, singular spectrum analysis (SSA) was used to model and predict the position nonlinear movements. The modeling accuracies of SSA were better than 3, 2, and 5 mm in the east (E), north (N), and up (U) directions, respectively; and its prediction accuracies were better than 5 mm and 1 cm for the horizontal and vertical domains, respectively.

In this paper, a single-frequency real-time kinematic positioning (RTK) robust adaptive Kalman filtering algorithm is proposed in order to realize real-time dynamic high-precision positioning of smartphone global navigation satellite systems (GNSSs). A robust model is established by using the quartile method to dynamically determine the threshold value and eliminate the gross error of observation. The Institute of Geodesy and Geophysics Ⅲ (IGG Ⅲ) weight function is used to construct the position and speed classification adaptive factors to weaken the impact of state mutation errors. Based on the analysis of the measured data of Xiaomi 8 and Huawei P40 smartphones, simulated dynamic tests show that the overall accuracy of the Xiaomi 8 is improved by more than 85% with the proposed robust RTK algorithm, and the overall positioning error is less than 0.5 m in both open and sheltered environments. The overall accuracy of the Huawei P40 is improved by more than 25%. Furthermore, the overall positioning accuracy is better than 0.3 m in open environments, and about 0.8 m in blocked situations. Dynamic experiments show that the use of the robust adaptive RTK algorithm improves the full-time solution planar positioning accuracy of the Xiaomi 8 by more than 15%. In addition, the planar positioning accuracy under open and occluded conditions is 0.8 m and 1.5 m, respectively, and the overall positioning accuracy of key nodes whose movement state exhibits major changes improves by more than 20%.

When and how was the Tibetan Plateau (TP), one of the least habitable regions on Earth, occupied by humans are important questions in the research of human evolution. Among tens of Paleolithic archaeological sites discovered over the past decades, only five are considered coeval with or older than the Last Glacial Maximum (LGM, ∼27–19 ka). As one of them, the Siling Co site in the central TP was previously announced to be ∼40–30 ka based on radiocarbon dating and stratigraphic correlation. Given the loose chronological constraint in previous studies, we here re-examined the chronology of the Siling Co site with the optically stimulated luminescence (OSL) dating technique. Four sections from the paleo-shoreline at an elevation of ∼4,600 m in southeastern Siling Co were investigated, with stone artifacts found from the ground surface. Dating results of nine samples delineated the age of ∼4,600 m paleo-shoreline to be ∼10–7 ka (∼8.54 ± 0.21 ka in average). This age indicates that the Siling Co site is not earlier than the early Holocene, much younger than the former age. The revised age of the Siling Co site is consistent with the wet and humid climate conditions on the TP during the early Holocene.

The Earth has gone through multiple ice ages in the past million years. Understanding the ice age dynamics is crucial to paleoclimatic study, and is helpful for addressing future climate challenges. Though ice ages are paced by variations in Earth’s orbit geometry, how various climatic system components on the Earth respond to insolation forcing and interact with each other remains unclear. A prevailing view argues that the initial responses occur in the northern high latitudes (i.e. the northern high-latitude hypothesis, NHH). This opinion is challenged by recent reports, such as the lead of climate change in the Southern Hemisphere (SH) relative to that in the Northern Hemisphere (NH), the southern control on Atlantic meridional overturning circulations (AMOC), and the potential significance of Southern Hemisphere (SH). Alternatively, the tropical hypothesis (TH) argues for a leading role of the tropics. Both the NHH and the TH belong to a single-forcing mechanism, and have difficulty in interpreting phenomena, such as the saw-tooth pattern of the ice ages. Here we present a new proposal concerning the Earth’s ice age dynamics: the bimodal forcing hypothesis (BFH). The essential assumption of this hypothesis is that for glacial-interglacial cycles, the cooling (glaciation) starts from the northern high latitudes, whereas the warming (deglaciations) starts from the SH. Particularly, the BFH emphasizes the significance of SH oceans in accumulating and transferring heat for deglaciations. Thus, it is capable to reasonably explain the saw-tooth pattern. We compiled 100 paleotemperature records globally for validation. The BFH is consistent with most of these records, and provides a straightforward and comprehensible way to interpret ice age on Earth.

With the completion of the BeiDou Global Navigation Satellite System (BDS-3), the multi-system precise point positioning ambiguity resolution (PPP-AR) has been realized. The satellite phase fractional cycle bias (FCB) is a key to the PPP-AR. Compared to the combined ionosphere-free (IF) model, the undifferenced and uncombined (UDUC) model retains all the information from the observations and can be easily extended to arbitrary frequencies. However, the FCB is difficult to apply directly to the UDUC model. An observable-specific signal bias (OSB) can interact directly with the original observations, providing complete flexibility for PPP-AR for multi-frequency multi-GNSS. In this study, the OSB product generation for the GPS (G), Galileo (E), and BDS-3 (C) systems is performed using 117 globally distributed multi-GNSS experiment (MGEX) stations, and their performances are evaluated. Then, the PPP-AR comparison and analysis of the two positioning models of the UDUC and IF are conducted. The results show that the stability of OSB products of the three systems is better than 0.05 ns. For the precise point positioning (PPP) ambiguity fixed solution, with comparable positioning accuracy and convergence time to the products of both the Wuhan University (WUM) and the Centre National d’Etudes Spatials (CNES) institutions, an average fixed-ambiguity rate is over 90%. Compared to the PPP float solution, the PPP-AR has the most significant improvement in positioning accuracy in the E-direction. The average improvements in the positioning accuracy under the IF and UDUC models in the static and kinematic modes are higher than 45% and 40%, respectively. The convergence times of the IF and UDUC models are improved on average by 48% and 60% in the static mode and by 40% and 55% in the kinematic mode, respectively. Among the IF and UDUC positioning models, the former has slightly better positioning accuracy and convergence time than the latter for the PPP float solution. However, both models have comparable positioning accuracy and convergence time after the PPP-AR. The GCE multi-system combination is superior to other system combinations. The average convergence time for the static PPP fixed solution is 8.5 min, and the average convergence time for the kinematic PPP fixed solution is 16.4 min.

Luminescence dating is a useful chronological tool for glaciogenic sediments, especially when the targeted sediments lack organic materials or are too old for radiocarbon dating. However, problems like partial bleaching make its application on glaciogenic sediments challenging. Poor luminescence characteristics and low saturation level of quartz limit its application in glacial environments, especially dating old glacial sediments. Developments of the single-grain technique and post-infrared infrared stimulated luminescence (post-IR IRSL) protocols offer opportunities for mitigating or overcoming these problems. Here we test the use of single grains of K-feldspar for luminescence dating of glacial sediments of penultimate glaciation: Guxiang glaciation, the largest known Quaternary glacier advance in SE Tibetan Plateau and was previously constrained to marine isotope stage 6 (MIS-6) by cosmogenic nuclide 10Be exposure dating [1]. We took 6 samples (GX601 to GX606) from glaciofluvial sand lens within the lateral moraines of Guxiang glaciation and 2 samples (GX607 and GX608) from overlying loess and paleosol. Dose recovery tests show that the two-step post-IR50 IRSL225 protocol was able to recover the given dose and assumed suitable for this study. The equivalent doses (Des) of each sample show large scatter, suggesting partial bleaching of these samples. It is therefore unsurprising that Des derived from the minimum age model (MAM) are smaller than those derived from the central age model (CAM). Measurement of the fading rates show that, g-values of the IR50 signal range between 3-6%, whereas those of the pIR50 IRSL225 signal are all less than 3%. After correction of the fading rates, the final ages derived from the pIR50 IRSL225 signal fall into MIS-6 if the CAM is used, and fall into MIS-5 if the MAM is used. In addition, we compared the single-grain K-feldspar and quartz ages of the younger overlying loess and paleosol samples. For both minerals, the MAM ages are smaller than the CAM ages. Moreover, the MAM ages of feldspar (~4 ka for GX607 and ~20 ka for GX608) are similar to the CAM ages of quartz, and thus larger than the MAM ages of quartz (~2 ka for GX607 and ~10 ka for GX608). This seems indicate the residual doses of feldspar are probably larger than those of quartz. For most of these samples, there is a trend that the brighter the grains, the lower their Des. The discrepancies between those results of CAM and MAM age models, quartz and feldspar, dim and bright feldspar grains, and comparation between luminescence and 10Be exposure ages, will be investigated and discussed. [ABSTRACT FROM AUTHOR]