When designing a robust total least-squares(RTLS) estimation algorithm based on M-estimation theory, the total least-squares(TLS) estimation is not suitable for residual prediction, and reweighting based on individual random variable residuals has theoretical flaws. We derive the TLS estimation iteration formula based on multiplicative error model, theoretically explain the equation residuals or total residuals, and explain that this residual has the properties of least-squares(LS) estimation residuals. Then, considering the robustness in both observation space and structural space, an RTLS estimation algorithm is designed based on equation residuals or total residuals. Finally, through Monte Carlo experiments, the RTLS algorithm is compared with other reweighting strategies in terms of robustness, efficiency, and iteration speed, demonstrating the advantages of the proposed RTLS algorithm.

For the five ultra-high-degree Earth gravity field models with a degree of 2 190, namely EGM2008, EIGEN-6C4, GECO, SGG-UGM-2, and XGM2019e_2159, which have been published internationally, a study on quasi-geoid refinement was conducted using the Shanxi survey area as an example. First, the accuracy performance of five models in Shanxi area was compared and analyzed using actual GNSS/leveling data. Then, based on the remove-restore technique, the residual height anomalies after removing the results of five ultra-high-degree gravity field models were fitted to the quasi-geoid using the multiquadric function method. A contour line-based method for selecting multiquadric function nodes was proposed, and the fitting accuracy was compared and analyzed. The results show that: 1) The accuracy distribution of five Earth gravity field models in Shanxi area is consistent, with larger errors mainly distributed in the high mountain areas in northern Shanxi. The XGM2019e_2159 model has the highest accuracy with a mean error of 9.1 cm, while the EGM2008 model has the lowest accuracy with a mean error of 11.3 cm. 2) The accuracy of five ultra-high-degree gravity field models does not significantly affect the final quasi-geoid accuracy. Among them, the quasi-geoid derived from considering the EGM2008, EIGEN-6C4, and SGG-UGM-2 models has the highest external consistency accuracy with a mean error of 5.0 cm. The quasi-geoid derived from XGM2019e_2159 model with the highest accuracy has the lowest external consistency accuracy with a mean error of 5.5 cm.

Aiming at the problems of single data structure and low resolution of ocean tide model in"specifications for the first and second order leveling", four recent high-resolution global ocean tide models are corrected using the high precision China offshore model, and the influence of four offshore correction ocean tide models on precise leveling and the effect of ocean tide loading correction are calculated and analyzed. The results show that the DTU10 offshore correction model is the most practical and accurate ocean tide loading correction model for precise leveling in China's coastal area, and the influence of ocean tide loading on leveling height difference above 400 km from the coast is negligible (the correction of ocean tide loading per kilometer is not more than 0.005 mm).

The gravity recovery and climate experiment(GRACE) mission and followed missions can provide unconstrained monthly time-varying gravity fields that are polluted by north-south striping noise. This noise is defined as a quasi-periodic oscillation along longitude, propagating continuously along latitude. Aiming at this characteristic, we introduce the moving average smoothing technique to suppress the noise in spatial domain, implementing different degrees of smoothing based on the different prior knowledge between ocean and land. Then, the proposed method is compared with common DDK filters in spatial, frequency, and time domains, showing a comparable filtering effect. The evaluation results show that the noise level of proposed method in ocean is about 20 mm, which is lower than that of DDK5-DDK7(26.20-50.25 mm). Although there are limitations such as the setting of sliding window size depends on experience, the proposed method does not need to know the variance information between signal and noise in advance and can provide a new idea for the design of novel filters.

We investigate the phenomenon of coseismic ionospheric disturbances(CIDs) caused by Japan Noto Peninsula M_W7.6 earthquake on January 1, 2024 using the total electron content(TEC) calculated by GPS observation data. The results show that: 1) Satellite G04, located northwest of earthquake epicenter, recorded a CIDs with maximum disturbance amplitude of approximately 0.07 TECu. 2) Satellite G16, located east of earthquake epicenter, recorded a CIDs with maximum disturbance amplitude of about 0.08 TECu. 3) The G16 and G26 satellites detected more significant CIDs in south of earthquake epicenter than in other directions, which is consistent with the direction of seismogenic fault(southwest direction). Significant CIDs are also detected at Kokubunji station, located about 286.714 km south of earthquake epicenter. This significance may be due to the large vertical displacement of thrust type earthquakes, which increases the disturbance amplitude of CIDs signal. 4) The CIDs detected by G04, G16 and G26 satellites have the propagation velocities of about 589 m/s, 623 m/s, 876 m/s and 829 m/s, and the corresponding center frequencies are about 3.14 MHz, 2.9 MHz, 2.9 MHz and 2.9 MHz in the northwest, east and south of earthquake epicenter, indicating that the ionospheric disturbances detected in different regions are consistent with the characteristics of ionospheric disturbances excited by seismic waves.

In response to the problem that traditional seismometer insulation cover cannot meet the instrument working environment indicators at low temperature and cannot maintain a constant temperature in working environment, an intelligent seismometer insulation cover has been developed using graphene material and popular 3D printing technology, taking into account the observation environment requirements of seismometer. According to indoor and outdoor testing and analysis, the intelligent insulation cover can meet the monitoring environment requirements of seismometer, with a temperature fluctuation of less than 1 ℃, a universal power supply demand of 12 V, intelligent constant temperature, lightweight instrument, simple operation, and wide applicability. It can be used in poorly conditioned observation chamber and low temperature outdoor environment.

This paper takes the Earth rotation parameters(ERP) obtained by each individual measurement means as research data, and outputs the processing results in the time domain and frequency domain respectively. Then the index parameters obtained from each analysis are compared with the data analysis results obtained by joint calculation in international Earth rotation service(IERS). The results show that the time-varying characteristics of ERP obtained by various measurement methods are different.

This article is based on the kinematic GNSS observation from the 13th Chinese Arctic Ocean scientific expedition, which marked China's first arrival at the North Pole. It compares and analyzes the observation quality of different signal from BDS and GPS in terms of carrier-to-noise ratio, multipath effects, pseudorange noise, ionospheric delay rate of change, and evaluates their kinematic positioning performance. The results show that the BDS's visible satellite count is still maintained at 8 to 14 close to the North Pole, and that the PDOP value is superior to that of GPS. In the Arctic region, the RMS of multipath combination observation for BDS is around 0.2 m. The RMS of multipath combination observation for B1C and B2a is smaller than the B1Ⅰ and B3Ⅰ signal, but their pseudorange noise is higher. The results of kinematic pseudorange positioning show that the positioning accuracy of BDS is comparable to the GPS, with the B1C/B2a ionosphere-free combination yields better positioning performance than the B1Ⅰ/B3Ⅰ combination.

The epicenter of 2022 Honghe M_S5.0 earthquake is located near the southern section of Red River fault zone, which consists of two nearly parallel faults: the Bolumu-Maocaoping fault and the Nanhun-Nabing fault. The Nanhun-Nabing fault is an active fault in the late Pleistocene, and significant water system dislocation deformation exists in the earthquake area. The field investigation after earthquake shows that a 1.2 km long surface rupture appeared on the ridge between Nanhun river and Nanchu river, and its distribution characteristics are consistent with the linear topography of Nanhun-Nabing fault. The deformation properties exhibited by the surface rupture in this area are consistent with the motion characteristics of earthquake rupture. Combined with the focal mechanism solution, it is believed that the Nanhun-Nabing fault is the seismogenic structure of Honghe M_S5.0 earthquake.

The strain monitoring data from the Guza station in 2022 to 2023 were analyzed using time series analysis. By comparing the difference in strain signals at the observation site during the seismic and non-seismic periods, it is concluded that during earthquakes above M_S4.5, there are obvious trend anomalies in both the detrended surface strain and the corrected principal strain direction. The likelihood of earthquakes increases when the detrended surface strain decreases at 1.1 times and the variance increases significantly. The trend of the corrected principal strain directions during seismicity is similar to the drug metabolism concentration curve model. The fluctuation period is small and the amplitude is large, which is significantly different from the nearly straight-line trend during the steady state.