In view of the non-linear and non-stationary characteristics of the ionospheric total electron content(TEC) data, based on the auto-regressive moving average(ARMA) model prediction method and the empirical wavelet transform(EWT) method, we propose a combined short-term ionospheric prediction method. Using the ionospheric TEC grid data provided by IGS, the results show that, compared with the average relative accuracy of single ARMA model, the average relative accuracy of the combined model in low solar activity and high solar activity years is increased by 4.8% and 2.8% respectively, and the average relative accuracy of the combined model in the first day is increased by 7% and 6.1%.

Based on the 15-day precise satellite clock bias (SCB) data from different aspects, we comprehensively analyze the prediction effect before and after using the SCB’s single difference prediction principle for six common prediction models, including the linear polynomial (LP), the quadratic polynomial (QP), the grey (GM), the spectrum analysis (SA), the time series ARIMA (ARIMA), and the Kalman filtering (KF) models. Accordingly, the following conclusions are drawn: 1) Using the principle can improve prediction accuracy. Specifically, they are the LP model, SA model, GM model and KF model used in the 3 h prediction for GPS SCB, the QP model and ARIMA model used in 3 h prediction for ⅡF Rb clock SCB, the LP model and GM model used in 6 h and 12 h prediction, the ARIMA model used in 6 h, 12 h and 24 h prediction. 2) The prediction results of the principle are related to the types of satellites and their onboard clocks, and for GPS BLOCK ⅡF Rb clocks, based on the prediction principle, the short-term prediction accuracy of the six models can be improved, especially for GM, LP and ARIMA models. 3) For the prediction of 3 h and 6 h, the RMS value corresponding to the DLP model (the LP model after using the principle) is the smallest, that is, the prediction accuracy of the DLP model is the highest, indicating that the single difference data of SCB is more in line with the short-term prediction of the LP model.

We use the new solar radiation pressure model ECOMC, combined with the ECOM-9 model, to apply five IGU precision ultrarapid ephemeris for precise orbit determination. We take the final IGS precise ephemeris as the true value, and compare the accuracy of GPS satellite orbit determination. The research results show that: compared with the ECOM-9 model, the use of the ECOMC solar radiation pressure model can improve the orbit accuracy of the satellite in the radial, tangential, and cross directions, with more obvious increase in the radial direction. The orbit determination results of fast and precise ephemeris can achieve the orbit determination accuracy of 5 cm, 3.5 cm, 2.5 cm, 1.5 cm and 1.5 cm respectively using the ECOMC new solar radiation pressure model, which is better than the orbit accuracy of ECOM-9.

In order to solve the problem of the accuracy reduction of the navigation system caused by the weak, intermittent, or interrupted satellite signals of the differential Beidou/SINS integrated navigation system in the airfield vehicle, we propose a high-precision integrated navigation method based on motion detection. The method is based on the differential Beidou/SINS integrated navigation system frame of motion detection, using the zero-velocity update and dynamic zero-velocity update to constrain the SINS errors according to the characteristics of the vehicle motion. We establish the state equation and measurement equation for optimal estimation of system errors, and realize the vehicle motion detection using gyro and accelerometer information of inertial measurement unit and the speed of SINS. We carry out vehicle experiments to verify the feasibility of the method. The results show that the positioning accuracy of Beidou/SINS integrated navigation system is better than 1 m when the satellite signal is valid. Compared to the traditional velocity constraint technology, the maximum longitude error of the integrated navigation system is reduced from 5.21 m to 1.35 m in the scene of 2.5 km satellite signal interruption.

We introduce the principle of adaptive estimation into the UKF algorithm to obtain an improved UKF algorithm. This algorithm can adjust the weight of the system model information in the navigation solution adaptively so as to reduce the influence of filter’s initial value deviation and system model abnormal disturbance on navigation solution. By applying the improved UKF algorithm to BDS/SINS integrated navigation, the simulation results not only verify the effectiveness of the improved UKF, but also show that the improved UKF can improve the accuracy of integrated navigation system.

On the basis of the BDS-3 precision orbit and clock products released by Xi’an Research Institute of Surveying and Mapping, we study the satellite differential code bias(DCB) correction model of B1C-B2a dual-frequency combination, and analyze the stability of DCB products released by the Chinese Academy of Sciences. The observation data of 7 days from 10 MGEX stations are used to compare and analyze the BDS-3 precise point positioning accuracy of B1I-B3I and B1C-B2a dual-frequency combination under the undifferenced and uncombined model and ionospheric-free combination model. The results show that the BDS-3 static positioning accuracy is better than 2.0 cm horizontally and 2.5 cm vertically, and the convergence time is about 31 min. The simulated dynamic positioning accuracy is better than 3.4 cm horizontally and 4.1 cm vertically, and the convergence time is about 60 min. The B1I-B3I and B1C-B2a dual-frequency combination positioning accuracy is nearly equal and the convergence time is close. Both can be used for BDS precise point positioning.

Aiming at the problem of data missing in GNSS coordinate time series, this paper proposes to apply the Prophet model to the interpolation of GNSS coordinate time series. Through the design of different data random missing proportion and continuous missing length, we use the Prophet model, Lagrange and cubic spline method to carry out comparative experiments. Experimental results show that the Prophet model has higher interpolation accuracy and better stability in GNSS coordinate time series, and has obvious advantages for continuous missing data interpolation.

Using GAMIT/GLOBK software, we calculate the coordinate time series of Anhui continuously operation reference stations(CORS) during 2013-01 to 2018-06. The noise is analyzed and the results show that the optimal noise model of AHCORS is the white noise+flick noise(WN+FN) model. Considering the influence of colored noise, the average velocity of AHCORS reference station under ITRF2008 frame is 31.72 mm/a with a direction of E22.76°S. The average velocity with respect to Eurasian plate is 6.28 mm/a with a direction of E2.65°N. For the vertical direction, the average velocity is -0.71 mm/a, with the Huaihe river as the boundary, showing a trend of uplift in the south and subsidence in the north. Among them, the uplift rate of the Dabie mountain area is higher than that of the Jianghuai and Huangshan areas, the uplift rate of the Jianghuai area is relatively gentle, and the average uplift rate of the area south of the Huaihe river basin is 2.94 mm/a. The subsidence in Huaibei area is obvious, the average subsidence rate is 10.92 mm/a, the maximum subsidence rate is 32.82 mm/a, which is at Dangshan station in Suzhou(SZDS). The obvious subsidence in this area may be caused by the extraction of mineral resources in recent years.

In order to enrich the data source of GNSS-IR technology, we propose a method for soil moisture retrieval based on multipath error of BDS triple-frequency carrier phase. The results show that there is a strong correlation between the delay phase derived from the multipath error and the soil moisture, and the correlation coefficient is 0.97. Because only a few epoch multipath errors are needed, the soil moisture retrieval accuracy comparable to GNSS-IR based on signal-to-noise ratio can be obtained, so the new method makes it easier to achieve high dynamic monitoring of soil moisture.

We propose a point cloud registration method based on the fusion of sample consensus initial alignment(SAC-IA) and normal distribution transformation(NDT) registration. First, we calculate the fast point feature histogram(FPFH) feature of the point cloud to be registered and the target point cloud; second, according to the feature of two pieces of point cloud and using the SAC-IA algorithm to find the initial transformation matrix, thereby completing the initial registration; finally, on the basis of the initial registration, we use the NDT algorithm to precisely register the two point clouds. Experimental results show that the registration accuracy of this method is significantly superior to the ICP algorithm, and the registration efficiency is also relatively improved.

To improve the detection accuracy of the ionospheric total electronic content (TEC) anomaly, we propose ARMA model to modify the predicted data to obtain the TEC reference background value. The TEC anomaly detection before the earthquake is realized by setting the threshold of relative error and absolute error restricting each other. We analyze the 2016-01-21 Menyuan MS6.4 earthquake to verify the validity of the method. The results show that there are obvious TEC anomalies at 5 days prior to earthquake. The ionospheric anomaly area with concentrated range is formed in the epicenter and nearby areas. The maximum TEC anomalies appear at the south of the epicenter. Meanwhile, the TEC anomaly areas are not consistent with the epicenter, which locates east of the negative anomaly area or south of the positive anomaly area.

In order to evaluate the modeling accuracy of ocean tide load displacement in New Zealand, we use the observations collected from 189 GPS stations in New Zealand with the time span over eleven years. Then, the ocean tidal loading (OTL) displacements at 8 major (diurnal and semi-diurnal) tidal constituents are estimated based on the modified precise point positioning (PPP) algorithm in the static mode. We then carry out the inter-comparison of the OTL displacements between the GPS estimates and modeled values derived from seven global ocean tidal models and four earth models. The study shows that: 1) The results from GPS agree best with TPXO7.2 model; the RMS misfit of M2, N2, O1 and Q1 are within 0.5 mm and 0.7 mm in the horizontal and vertical directions, respectively. 2) Differences between different earth models exist mainly in M2 and N2 tidal constituents. 3) The residual vectors of OTL displacements estimated between GPS estimates and the model correction values at most sites present spatial consistency in both the amplitude and direction, and residual anomalies are observed at a few sites, which probably can be attributed to the deviation of the priori SNREI earth model.

In this paper, we extract the deformation information of Baige landslide, Polo town, Jomda county, Tibet, by PS-InSAR and SBAS-InSAR techniques using ALOS-2 PALSAR2 images of 12 scenes from 2015 to 2019 and Sentinel-1A images of 38 scenes from 2018 to 2019 as the main data sources. The main conclusions of this paper are as follows: 1) Under the PS-InSAR technique, the average deformation rates of ALOS-2 data and Sentinel-1A data range from -68.9~37.9 mm/a and -64.5~24.2 mm/a. The average deformation rates of ALOS-2 and Sentinel-1A data range from -84.2~-40.0 mm/a and -84.0~-13.0 mm/a under the conditions of SBAS-InSAR technology. 2) Timing sequence analysis and quantitative analysis are performed on the four feature points extracted from the two data results. The results of the two technique showed a consistent trend. Thus, the reliability and accuracy of the two time-series InSAR techniques in landslide monitoring are verified.

Based on 24 scenes Sentinel-1A data covering the Hefei area, we use PS-InSAR and SBAS-InSAR time series processing methods to obtain the land deformation distribution information of Hefei city from 2017-11 to 2019-10. We analyze the temporal and spatial evolution law of land subsidence in the main urban area. At the same time, we obtain the spatial distribution of ground deformation along Hefei metro network. The results show that there are different degrees of deformation along the subway line, and the stations with serious deformation are mainly concentrated in the western and southwest regions, where the maximum subsidence rate reaches 35 mm/a. We carry out deformation field analysis of Chihe-Xishanyi fault, and the cross fault leveling data with space-time synchronization are compared and verified. The analysis shows that the vertical deformation monitoring results of the two kinds of data have certain consistency, and the vertical rise and fall of the data may be controlled alternately by fault tension and compression.

We propose a L-curve characteristic value correction iteration method, using the maximum curvature point of L-curve to determine the final estimation results. The experimental results of SBAS-InSAR deformation inversion show that the L-curve characteristic value correction iteration method can be used to determine a stable estimation result with a small residual, thus improving the accuracy and stability of the estimation result.

In order to improve the effectiveness and reliability of noise reduction from GNSS deformation monitoring data, we propose the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) method. First, the GNSS deformation sequence is decomposed into several characteristic modal functions by CEEMDAN. Second, we introduce the permutation entropy theory to determine the high and low frequency boundary value K, then use wavelet analysis to denoise the high frequency component. We reconstruct the denoising sequence with the low frequency component after denoising. Finally, through simulation data and measured slope GNSS deformation monitoring data, we compare and analyze CEEMDAN, EMD and wavelet denoising methods using signal-to-noise ratio, root mean square error, correlation coefficient and other indicators. The results show that CEEMDAN is superior to EMD and wavelet denoising methods, proving the effectiveness and reliability of the method proposed in this paper.

We use GPS data as boundary conditions to simulate the displacement and stress fields of the Longxian-Baoji fault zone and its adjacent area by the finite element method, and analyze the distribution characteristics of the current crustal activity and the tectonic stress field in this area. The results show that: 1) The tensile stress of Weihe basin at the southern of Longxian-Baoji fault zone and Qishan-Mazhao fault is weak. 2) The stress properties and direction of the border zone between the southwestern margin of the Ordos block and Longxian-Baoji fault zone are consistent with the Longxian-Baoji fault zone, which shows the characteristics of the tensive activity paralleled to the strike of the fault zone. 3) The maximum principal stress shows that Longxi block and Qinling mountains tectonic zones present strong tensile stress. 4) The second principal stress shows that the compressive stress of SEE direction is significant on the southern side of the border zone between the southern of the Longxian-Baoji fault zone and Qinling mountains tectonic zone.

We discuss the seismogenic structure of the Yingcheng M_S4.9 earthquake on 2019-12-26 from aspects of seismology and geology. The sequence is relocated by HYPO2000 method. The results show that aftershocks are mainly distributed between Zaoshi and Changjiangbu faults, and are distributed in NW direction, which is basically consistent with the long axis direction of the intensity Ⅵ isoseismal in the field survey. The focal mechanism solution inverted by kiwi method shows that the main rupture is characterized by strike slip and thrust. The strike of plane Ⅰ is NE, which is consistent with Qianbei fault in the west of epicenter, but it is far away, and it is not consistent with the occurrence and stress mode of the fault. The strike of plane Ⅱ is NW, which is similar to Zaoshi fault and Changjiangbu fault. Through the analysis of dynamic mode of these faults, it is considered that under the control of NWW principal compressive stress in Jianghan basin, both Zaoshi fault and Changjiangbu fault are characterized by left-lateral strike slip. The strike of the main seismogenic plane is in the middle of two faults by an anticlockwise turn-slip due to the different strike. At the same time, the inclination of slip plane is also different with the actual fault plane, and aftershocks are partial to the east of the main shock. The analysis shows that the combined tectonic activity of Zaoshi fault and Changjiangbu fault triggered the Yingcheng M_S4.9 earthquake sequence.

We collect a total of 2 291 focal mechanism solutions of M_W≥3.0 earthquakes from the NIED F-net broadband seismic network center. The MSATSI tectonic stress inversion method is adopted to obtain R value reflecting the relative stress and the azimuth and dip angles of the three principal stress axes. The polar projection P and T axes of each grid can also be acquired. This study is based on 3D stress inversion, using the method of matrix grid partition and taking latitude, longitude and depth as coordinates. The focal mechanism solutions in each region are projected into the corresponding matrix region. We calculate the change and distribution of the stress field of each matrix grid point. The results show that the shallow area connected with the plate is not only pushed and subducted by the Pacific plate, but also subject to oblique thrust by the north American plate. The deep earthquakes in northeast China are the results of Benioff zone subduction.

In this paper, the static stability test and the dynamic stability test are carried out on the six CG gravimeters. The test results show that the CG-6 gravimeters inherits the static stability advantages of the CG-5 gravimeters. The error in the fitting of the static curve into a straight line is less than 3 μGal, and the maximum fitting difference is less than 5 μGal. The dynamic accuracy and dynamic zero drift rate of the CG-6 gravimeters are significantly better than the CG-5 gravimeters.

In this paper, we use the data recorded by 23 national seismic stations and 17 experimental seismographs to analyze the characteristics of background noise and the possibility of monitoring the operating state of seismographs by the fractal method. The results show that the fractal method has strong time domain, a high degree of quantification, strong anti-interference ability, and is unrestrained by the observation system parameters. It can test the operation state of the observation system and decrease the situation of interruption of normal records and non-natural interference.