Starting from the theoretical basis of nonlinear adjustment precision evaluation, we review the current research status of the two types of precision evaluation methods. We describe the basic principles of the corresponding method and analyze the advantages and disadvantages of each method. In addition, we look forward to the research direction of nonlinear adjustment precision evaluation.

Aiming at the linear Gaussian state model of integrated navigation system with inaccurate system noise and measurement noise statistics, this paper proposes a modified variational Bayesian adaptive filter(MVBAKF) for integrated navigation system.Firstly, the Wishart distribution is selected as the conjugate priors of Gaussian covariance matrix with known mean value, and the joint probability distribution function of measuring noise variance, state vector and prediction error covariance matrix is given. Then, the formula of measurement noise variance and state vector prediction error covariance matrix is given by using the variable decibels method, and then the MVBAKF algorithm with iterative characteristics is proposed. Finally, the simulation experiment of GNSS/SINS integrated navigation system based on MVBAKF algorithm is carried out. Experimental results show that MVBAKF algorithm can accurately estimate the variance of measurement noise, and can effectively overcome the influence of inaccurate system noise statistics on the filtering accuracy compared with traditional VBAKF algorithm, and thus improve the filtering accuracy of integrated navigation system.

Considering the high stability of high-performance hydrogen clocks and the strong correlation between clock offset series epochs, the receiver clock offset with additional prior information constraint is tested for precise point positioning(PPP) timing. The results based on B1C/B2b combination of BDS-3 show that compared to traditional timing models, the precision timing models with additional prior information have higher timing performance, especially for the short-term stability which has an improvement up to 60%. In addition, the PPP accuracy of B1I/B3I and B1C/B2b combinations of BDS-3 is basically equivalent, which can achieve positioning accuracy better than 0.5 cm and about 2 cm in horizontal and vertical direction, respectively. Owing to the better observation data quality of B1C/B2b, the positioning accuracy is improved by 13.8% compared to the B1I/B3I combination.

To compare the positioning performance of the new signals and old signals of Beidou-3 satellite navigation system, we conduct a comprehensive evaluation of BDS-3 precise point positioning with new signals B1C/B2a using two-week observation data from 17 MGEX stations. The results show that the accuracy in E, N, U directions of static PPP with BDS-3 B1C/B2a was 1.3 cm, 0.8 cm, and 1.9 cm, respectively, while that of kinematic PPP was 2.6 cm, 1.8 cm, and 4.2 cm, respectively. The static positioning accuracy in U direction showed an improvement of 13.6% compared to the BDS-3 B1I/B3I combination, the accuracy in E, N directions were similar. In the kinematic mode, the accuracy in E, N, U directions were similar, with differences within 1 mm. In terms of three-dimensional(3D) error, BDS-3 B1C/B2a static PPP achieved centimeter-level accuracy within 40 minutes, while kinematic PPP achieved decimeter-level accuracy within 5 minutes. The static PPP with the dual-system BDS-3 B1C/B2a+GPS L1/L2 achieved centimeter-level accuracy in three dimensions within 20 minutes, while the kinematic PPP achieved centimeter-level accuracy within 30 minutes. Comparing with dual-system BDS-3 B1I/B3I+GPS L1/L2, the positioning accuracy and convergence speed are basically the same. Overall, the positioning performance of B1C/B2a frequency is superior to that of B1I/B3I frequency.

This paper collects dynamic data from low-cost receivers in three different speed ranges and analyzes the data reception capability, data quality, and navigation positioning performance of multi-system interoperable signals, B1C/L1/E1, and B2a/L5/E5a, within various speed intervals. The results show: 1) As the speed increases, the reception capability of interoperable signals gradually deteriorates. BDS-3 can maintain visibility of more than nine satellites on average. Among the interoperable signals, B1C/L1/E1 exhibits superior data integrity but is more susceptible to data interruptions.2) As the speed increases, the carrier-to-noise ratio of interoperable signals decreases, and cycle slip ration increase. However, the pseudo-range noise, carrier phase noise, and multipath effects are less affected by speed. Notably, B1C/L1/E1 exhibits minimal carrier phase noise and multipath effects. 3) The influence of carrier speed on positioning accuracy has no obvious regularity. The speed and the degree of environmental occlusion affect the positioning accuracy. The multi-system interoperability signals combination positioning has more improvement than the single system positioning performance; BDS-3 has high accuracy in the middle and low speed range, and its precision of PPP is better than other systems by more than 17%.

The precipitable water vapor(PWV) retrieved by MODIS is continuous planar data, but the accuracy is not high. The PWV accuracy of GNSS water vapor detection technology is high, but it is discrete point data. Therefore, we combine the advantages of both, propose a MODIS water vapor correction method that combines inverse distance weighting and Fourier transform, and use GNSS PWV to correct MODIS PWV products. The GNSS data and MODIS water vapor products in Hong Kong are used for experimental verification. Firstly, the spatial interpolation problem is considered to make GNSS PWV and MODIS PWV consistent at spatial points. By comparing the accuracy of six interpolation algorithms with different MODIS pixel points, it is found that the algorithm with 5 interpolation parameters has the best effect, and the inverse distance weighting method has the highest accuracy, with an average deviation of -0.99 mm. Secondly, considering the water vapor correction problem, three models are constructed to correct MODIS PWV. It is shown that the root mean square error improvement rate of Fourier transform model can reach more than 70%. The MODIS water vapor correction method of the new model can weaken the influence of local data, and more accurately reflect the water vapor distribution in the region.

Using high-density resistivity layer analysis imaging method, we detect the electrical structure of the underground medium in the geoelectric observation site of Mengcheng national geophysical observatory in Anhui. We carry out the detection by using a Wenner device and continuous rolling measurement, resulting in high-precision apparent resistivity data and electrode elevation information. Through forward and reverse calculations of the detected data, we obtain the distribution characteristics of the electrical structure of the study area in different axial directions and depths. Through the inverse calculation of the probe data, we obtain the resistivity distribution characteristics in different axial directions and at different depths, and obtain a relatively fine image of the electrical structure of the study area, which is geologically interpreted in combination with the historical probe data and drilling data. This provides a more scientific and fine background basis for the in-depth analysis and research of the resistivity observation data of Mengcheng ground.

The original curve analysis method and normalized variation rate method were applied to analyze the data changes of four earth resistivity stations within 400 km of the epicenter of Maduo M_S7.4 earthquake on May 22, 2021. The following results were obtained:1)Before the Maduo earthquake, the data of four earth resistivity stations showed different degrees of anomalous changes, among which the original curve changes of the Maqu NW, Jinyintan EW, Ganzi N10°E, and Lanlongkou EW channels were the most obvious, which manifested hour value jumping changes, accelerated changes in the daily mean values and curve turning changes, as well as trend changes in the monthly mean values of the broken and preserved annual variation patterns;2)The normalized rate curves of Maqu NW, Jinyintan EW, Ganzi N10°E, and Lanlongkou EW all exceeded the threshold before the Maduo earthquake, but their respective normalized rate patterns are different;3)The comprehensive analysis concludes that the anomalous changes in the earth resistivity data of the four stations are related to the gestation and activity of the Maduo M_S7.4 earthquake.

Using least squares and iterative algorithms for 5 d simultaneous co-location comparison observations at Anqiu seismic station, we process the data of A10-057 absolute gravimeter, FG5-265 absolute gravimeter and superconducting gravimeter(iGrav). The final calibration factor factors of FG5-265 and A10-057 precision measurement iGrav-053 are -883.929 4 ns^-2/V and -884.134 ns^-2/V, respectively, and the calibration accuracy is 0.048 26% and 0.093 7%, which are better than 0.1%. At the same time, we compare the differences between the calibration work of FG5-265 and A10-057 in terms of various measurement indexes and the selected measurement logarithms on the calibration results, and exemplify the requirements of calibration factor for multiple scenarios, which finally proves that the A10 model absolute gravimeter has the capability of calibrating relative gravimeters and provides a reference for the subsequent calibration of relative gravimeters.

By means of the field geological and geomorphological investigation combined with UAV aerial photography survey, geological radar exploration and shallow seismic exploration, we comprehensively reckon that the eastern margin fault of Jinshan uplift extends with the strike of 40° in a whole, starting from the northern Xinkou village, extending to the southwest through the western Jinshanpu village and western Qianyuni village, and turning to the SWS and into the basin area around northern Buluo village. Through trenching and chronology tests, we think the fault latestly misplaced the early Late Pleistocene strata.

Using the three-component teleseismic wave shape data recorded by 85 mobile seismic stations in northwest Yunnan(25.0°N to 26.9°N, 99.20°E to 100.74°E), we extract the P-wave receiving function, and obtain the Moho depth and Poisson’s ratio by H-k scanning method. Then, we apply the receiving function common transformation point(CCP) stacking method, plotting a total of 6 vertical sections NW and NE were plotted. The results show that the crust thickness in the study area varies from 38.5 to 52.4 km, with the crust thickness being thicker in the northwest and thinner in the southeast. Poisson’s ratio varied between 0.24 to 0.34, showing a four-quadrant distribution. The wave velocity ratio decreases with the increase of crustal thickness in the study area, showing a certain negative correlation. Yunlong M5.1, Eryuan M5.5 and Yangbi M6.4 earthquakes all occurred in the high gradient zone of Poisson’s ratio. According to the CCP profile, the Moho in the study area fluctuates significantly in the NW direction, becoming shallower from the north to the south. The uprise amplitude is about 5 to 10 km. The fluctuation of NE toward Moho is relatively smooth, with an average depth of about 42 km. The stratification in the Earth’s crust is complicated, and there are few continuous interfaces. There is a wide negative amplitude band in the middle and upper crust below the Yangbi earthquake, which may provide seismogenic environment for the occurrence of earthquakes. The average depth of the D410 discontinuity plane is about 420 km, the average depth of the D660 discontinuity plane is about 660 km, and the thickness of the mantle transition zone is 210 to 260 km.

To provide a statistical formula between the shear wave velocity and depth of typical cohesive soil, silt, sandy soil, and gravel soil in Xiangyang area, Hubei Province, based on 102 measured borehole wave velocity data, we use multiple univariate regression models to fit and analyze the relationship between shear wave velocity and depth of common soil layers. Then, we discuss the influence of soil state on the correlation between the two. Finally, we verify the rationality and reliability of the statistical formula using actual drilling data. The results show that: 1) Except for artificial filling, there is a strong correlation between the shear wave velocity and depth of other conventional soil types in Xiangyang area, and the degree of dispersion increases with the increase of depth; 2) As the density or plasticity of the same soil type increases, its average shear wave velocity also increases; 3) Considering the soil state can make the prediction results of the regression model more specific and closer to the true values, but there is uncertainty in the changes in the goodness of fit of the model; 4) Regionality has a significant impact on the statistical relationship between soil shear wave velocity and depth. The shear wave velocity regression models provided in this article for various soil types in the Xiangyang area have better prediction accuracy and error stationarity compared to the national soil type models. They can provide valuable reference basis for seismic disaster risk survey, site soil dynamic properties research, and determination of seismic motion parameters in the Nanxiang basin and surrounding areas.

We constructed models for changes in atmospheric and terrestrial water mass in the Three Gorges region. Then, using GNSS, GRACE-FO, and environmental mass change models, we calculate and analyze the vertical crustal deformation caused by environmental load from 2019 to 2022 in the region. At last, we discuss the differences in calculating environmental load vertical deformation using the spherical harmonic method based on GRACE-FO data and Green’s function method combined with the mass change model. The research reveals the vertical deformation of terrestrial water load of the two methods exhibits a certain consistency in spatiotemporal distribution, but the mass change model shows higher accuracy and spatial resolution. We calculate the environmental total load vertical deformation at CQWZ and HBZG stations, based on the quality change model. The correlation coefficients between deformation and GNSS measured results reached 0.88 and 0.83, respectively. The vertical deformation rates of the crust in the Three Gorges reservoir area and Dongting lake basin from 2019 to 2022 are 0.5 to 0.7 mm/a and 0.6 to 1.5 mm/a, respectively. We attribute this to the decrease in water level in the region in 2022, leading to crustal rebound. The crust near the Three Gorges reservoir exhibits a pattern of rising in summer and sinking in winter, with vertical deformation amplitudes ranging from -5 to 18 mm, primarily driven by reservoir water storage and atmospheric load.

In this paper, the glacier deformation is obtained by using offset-tracking technology as a supplement to SBAS-InSAR, and the pre-disaster deformation of Sedongpu basin is calculated by using two technologies from January 2018 to October 2018, and the pre-disaster deformation characteristics and influencing factors are jointly analyzed. The results show that the glaciers and gullies in Sedongpu basin were deformed before the ice avalanche occurred on October 17, 2018. The trend of the main deformation area of glacier is first accelerated, then gentle and then accelerated, with the deformation of -7.69 m from July to September. The sediments in channels showed a long-term downward trend, and the deformation rate accelerated after July. The temperature rise is the main factor for the occurrence of debris flow disaster. The combination of SBAS-InSAR and offset-tracking can meet the monitoring requirements of different deformation magnitudes, and can be used for early identification and deformation inversion of ice avalanche disasters, providing a reference for ice avalanche disaster prevention and control in the Tibetan plateau.

Using StaMPS technology, based on the images of 133 ascending orbit and 95 descending orbit covering Beijing capital international airport from 2017 to 2021, we research the ground subsidence around the airport and the stability of cracks in the interior of the site. The results show that the image monitoring results of ascending and descending orbit are in good agreement. A subsidence funnel is formed in the south of the airport and the south of the Wenyu river. The maximum deformation rate inside the funnel is over 40 mm/a, and the subsidence funnel is distributed along the Wenyu river. We verify the internal coincidence accuracy of the monitoring results of the ascending and descending orbit images. The results show that the deformation rate difference of more than 90% common pixels is between ±10 mm/a, which proves the consistency of the monitoring results of the images. The time series deformation results of feature points show that the subsidence near Jinzhan township, Fuhao village and Huangjinhuayuan community is serious, and the maximum cumulative shape variables exceed 250 mm, 150 mm and 110 mm, respectively. It can be seen from the overall deformation results of the airport and the time series and profile results on both sides of the ground fractures that the difference deformation of the surface on both sides of the ground fractures is significantly compared, and the boundary of the deformation difference is more consistent with the location of the ground fissures.

The strain observation data of Xuzhou station recorded abnormal phenomena before the M5.5 earthquake in Pingyuan, and the abnormal phenomena continued to return to normal after the M2.6 earthquake occurred in Heze. The timing of the anomaly is highly consistent with the occurrence of two earthquakes. By using precision analysis, difference analysis, minute value anomaly analysis and wavelet analysis, we determine that the abnormal variation of the strain data of Xuzhou platform before and after the earthquake is related to the earthquake.

The background noise of the second sampling data of four kinds of broadband instruments in Xinjiang during quiet period is analyzed, and the time-frequency characteristics of the signals recorded by various instruments under seismic waves and wind disturbance events are discussed. The results show that the noise level of RZB-2 borehole strainmeter is the best, and the response ability of VP type vertical pendulum to high-frequency signals(microseisms frequency range) is the best. Whether the instrument can record more geophysical signals or high frequency information is not only related to its own noise level, but also related to its response ability to the signal in this frequency band.

The solid tide signal of VP inclinometer is limited by the complex monitoring environment, which contains significant environmental noise. To obtain the real solid tide curve, we propose an improved complete ensemble empirical modal decomposition adaptive noise(ICEEMDAN) based on grey relation analysis for VP inclinometer to suppress signal noise. The method firstly uses ICCEMDAN to decompose the noise-containing signal to obtain several intrinsic mode functions(IMFs), which are sequentially arranged and labeled. Then, based on these IMFs, the evaluation indexes of correlation coefficients, mutual information, R², Adj-R², MSE, SSE, RMSE, MAE, MAPE, we compute sample entropy to construct a reliability evaluation index matrix of the IMFs. Finally, grey relation analysis(GRA) is used to calculate the correlation coefficients and degrees between various evaluation indexes and different IMFs. We sort the IMFs based on the correlation degree, and linearly reconstruct the top ranked IMFs to suppress signal noise. Both the simulation and actual denoising experiments show that the GRA-ICEEMDAN model is better than the classical noise reduction models, such as Kalman filter, 70 order low-pass FIR filter, and Savitzky-Golay. The noise component and effective component can be distinguished significantly, and the reconstruction error and original signal loss after decomposition are very small, so it can be extended to the signal noise reduction of other instruments.