15 January 2022, Volume 42 Issue 1
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jgg. 2022, 42(1): 1-4.
The standard deviations of the observation function can be calculated by the law of covariance propagation. However, the approximate function method based on Taylor series expansion requires complex derivative operations when solving the standard deviation of nonlinear function. The Monte Carlo method can avoid the derivative operation, but it is not objective in the selection of the number of simulations. Moreover, the Monte Carlo method cannot directly control the simulation results. To overcome these disadvantages, we introduce the Stein two-stage method into the covariance propagation theory of nonlinear functions. Combined with the Monte Carlo method, we design the Stein Monte Carlo (SMC) algorithm flow of nonlinear function covariance propagation. We apply the SMC method in the two-dimensional polynomial function and covariance propagation of GNSS baseline vector. Results verify the effectiveness of the SMC method. This method provides a new idea for the covariance propagation of nonlinear models.
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jgg. 2022, 42(1): 5-8.
As integer ambiguity is affected by atmospheric delay error, it is difficult to correctly fix ambiguity between BDS middle-range baseline. We propose the algorithm of triple-frequency ambiguity resolution between BDS middle-range baseline. We use the combination of MW to determine B2-B3 extra-wide-lane integer ambiguity, and then solve the B1-B3 wide-lane integer ambiguity using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation. We use the ionosphere-free combination observation to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and finally the real-time dynamic positioning is realized. We test this algorithm by the measured BDS middle-range baseline. The results indicate that the method can fix the triple-frequency carrier phase ambiguity between middle-range baseline correctly and effectively, and positioning accuracy to the centimetre level can be achieved.
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jgg. 2022, 42(1): 9-14.
To analyze the orbit determination performance of different solar radiation pressure models under different attitude control modes of Beidou satellite, we analyze the applicability of ECOM 5 parameter model, Box-Wing+ECOM 5 parameter model and extended ECOM model for Beidou IGSO and MEO satellites orbit determination from the aspects of internal and external orbit accuracy. The results show that with the satellite in non-earth eclipse segment, BDS-2 satellite using ECOM 5 parameters has the best internal and external accuracy, while the orbit accuracy of BDS-3 MEO satellite using Box-Wing+ECOM 5 parameters and extended ECOM 5 parameters is slightly better than ECOM 5 parameters; the difference of internal accuracy is less than 1 cm. When the satellite is in the earth eclipse segment, the extended ECOM has the best applicability for BDS-2 and BDS-3 MEO satellites. Compared with other solar radiation pressure models, the accuracy of along and cross internal accuracy is improved by about 20% and 70%. For BDS-3 IGSO satellite, the orbit accuracy is much lower than other Beidou satellites due to the small number of observations, but on the whole, ECOM 5 parameter model performs slightly better.
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jgg. 2022, 42(1): 15-20.
Aiming at the problem of susceptibility to satellite signals in GNSS vehicle navigation in urban environments, we use the GNSS/INS combined algorithm to improve positioning performance of urban vehicles in complex environments. Based on actual measurement GNSS data from the urban environment, we evaluate and analyze the positioning results, and use the conventional Kalman filtering algorithm of the GNSS/INS combination to realize the navigation of the satellite lock-out area. At the same time, we propose an adaptive Kalman filtering algorithm based on innovation, which can effectively enhance the navigation and positioning capabilities of vehicles in areas with fewer satellites and severe signal interference. This method uses the relationship between measurement and prediction to construct an adaptive factor to improve positioning accuracy. The results show that the conventional Kalman filter can guarantee sub-meter navigation accuracy when the satellite signal is out of lock in 20 s. For satellite signals with severely interference, the positioning accuracy of the adaptive Kalman filtering algorithm is increased by 30% when compared with the conventional Kalman filter. The adaptive Kalman filtering algorithm can meet the needs of high-precision and high-reliability vehicle navigation and positioning services in the complex urban environment.
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jgg. 2022, 42(1): 21-24.
Aiming at the problem of signal separation and insufficient accuracy of traditional models, we propose a new GNSS-R sea level altimetry inversion model combining wavelet transform and an improved Burg algorithm. Compared with the traditional least squares fitting method, the SNR oscillation term obtained by wavelet transform is more complete and accurate. The improved Burg algorithm can effectively suppress peak shift or spectrum splitting, and improve the accuracy of spectrum analysis. We analyze the GNSS data and tide gauge data provided by the Onsala Space Observatory in Sweden. The results show that there is a high agreement between the inversion result of the optimized model and the measured data of tide gauge, and the accuracy is increased by about 20% compared with the traditional GNSS-IR sea level altimetry inversion model.
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jgg. 2022, 42(1): 25-28.
This paper introduces CEEMDAN to replace the commonly used quadratic polynomial method to decompose the original signal-to-noise ratio signal, directly extract the corresponding intrinsic mode function, and then use GNSS-MR technology to retrieve snow depth. Experiments with Colorado NWOT station GPS data show that, compared with the traditional method, the root mean square error of this method is decreased by 30.7% and the correlation coefficient with actual snow depth is 0.965, which verifies the effectiveness of the method in this article.
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jgg. 2022, 42(1): 29-34.
The smoothing parameters of range split spectrum (RSS) in InSAR ionospheric correction, including multilook numbers and filtering window size, are selected subjectively, so we use international reference ionosphere (IRI) as a reference to evaluate the similarity between RSS and IRI by visual comparison and statistics analysis. Considering the ionospheric distribution, we provide a relatively objective method to select smoothing parameters for RSS. 32×16 (azimuth*range) multilook and 600 pixel size filtering window for two pairs of ALOS-2 PALSAR stripmap data. The ionospheric delay is corrected well. The research shows that the IRI model can be used as a reference to select RSS smoothing parameters in both invisible deformation and slow deformation regions.
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jgg. 2022, 42(1): 35-40.
We retrieve tropospheric delay data from 155 stations from 2014-2018 Crustal Movement Observation Network of China (CMONOC). We use the BP-Adaboost algorithm to integrate multiple weak neural network predictors into a strong one in order to establish a new tropospheric delay model without meteorological parameters. The accuracy of the BP-Adaboost model is evaluated using the tropospheric delay products of 141 CMONOC stations in 2019, 62 stations excluded in modeling and 86 radiosonde stations in China. The results show that the biases of the new model are 0.62 mm, -1.16 mm and 12.32 mm, and the root mean square errors are 25.30 mm, 26.72 mm and 46.29 mm, respectively, which are better than the common models without meteorological parameters. In addition, the BP-Adaboost model could achieve higher accuracy in inland areas or areas above 2 km above sea level, meeting the real-time tropospheric delay correction needs of Chinese satellite navigation users.
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jgg. 2022, 42(1): 41-47.
In southern China the terrain is high in the west and low in the east, and there are differences between the coast and the inland. Using 19 sounding stations in southern China from 2015-2017, we analyze the relationship between Tm and station height, ground temperature, seasonal variation and latitude. For the annual sounding data, we establish a linear model (Tm-SC1) that only considers ground temperature and a new Tm model (Tm-SC2) related to ground temperature, elevation, seasonal changes, and latitude on the basis of the Bevis formula. Using the sounding data in 2018 as a reference, we analyze the accuracy of the models. We compare the accuracy with the widely used Bevis formula and GPT3 model. The results show that the average annual deviation and root mean square error (RMS) of the Tm-SC1 model are 0.76 K and 2.57 K, respectively. Compared with the Bevis model and the GPT3 model, the accuracy (RMS value) is increased by 13.8% and 2.2%, respectively. The annual average deviation and root mean square error (RMS) of the Tm-SC2 model are -0.10 K and 1.64 K, respectively. Compared with the Bevis model and the GPT3 model, the accuracy (RMS value) is increased by 44.9% and 37.6%, respectively. The theoretical RMS error and relative error of water vapor calculation caused by the Tm-SC2 model used in GNSS water vapor calculation are 0.16 mm and 0.43%, respectively. Therefore, the Tm-SC2 model is more suitable for GNSS water vapor detection and meteorological research in southern China.
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jgg. 2022, 42(1): 48-53.
To obtain the distribution characteristics of land subsidence in Beijing, we use the small baseline subset (SBAS) InSAR technology to analyze the sentinel-1 data stacks covering the period from June 2017 to June 2020. The results show that there are five subsidence areas in Beijing, and the maximum annual deformation rate is -111.3 mm/a. We compare time series InSAR measurements and GPS measurements. Comparing the annual rates of 2018 and 2019, the paper also determines that the settlement area is decreasing in each settlement range, and the area of slow settlement is much larger than that of accelerated settlement. The investigation of local subsidence indicates that subsidence in one of the five subsidence areas is still accelerating while the speed of subsidence in the other four subsidence areas is decreasing.
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jgg. 2022, 42(1): 54-58.
Using PS-InSAR time series technology to process the Sentinel-1A image data from 2018-01 to 2019-12 in Changzhou city, we obtain the ground deformation information of Changzhou city. The results are consistent with leveling data in the same period; the difference between maximum value and average value of the two methods are 6.1 mm and 2.7 mm respectively, and the root mean square error(RMSE) is 1.7 mm. Analysis of the temporal and spatial evolution of land subsidence in Changzhou city shows that the uplift areas are mainly located in cities and towns, with an average cumulative uplift of about 7.3 mm; the subsidence area is mainly located in rural areas, with an average cumulative subsidence of about 7.6 mm; the ground subsidence in some areas such as the southern part of Wujin district is still severe, and the average cumulative subsidence exceeds 15 mm. Finally, we analyze the influence of the second pore confined water on land subsidence, and the correlation coefficient between the two is 0.55; analyzing the rebound situation of each layer of the layer-wise mark, the results show that most of the deep strata are in the rebound stage, and the shallow strata are currently the main layers of soil compression. This result shows that the second confined water has a certain impact on land subsidence and that the impact of soil compression in shallow strata on land subsidence is becoming more obvious.
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jgg. 2022, 42(1): 59-64.
To explore the influence of geodetic data with different dimensions and precisions on the inversion of fault slip distribution, we take three typical faults as subjects to discuss and analyze. We also experiment with slip distribution inversion where the deep slip varies along depth direction of the three categories faults from the different accuracy InSAR and GPS geodetic deformation. Comparing the results of three categories of faults, we find that the conclusions are highly consistent. The results show that at the same depth, the residual error by InSAR and GPS geodetic deformation with high accuracy is small, and the residual error of InSAR geodetic deformation with normal accuracy is larger. As center depth increases, the detection capability of deep slip inversion decreases gradually. The detection capability of deep slip inversion based on deformation (InSAR or GPS) with high accuracy is higher than that based on InSAR deformation with normal accuracy. When the accuracy of InSAR and GPS deformation is the same, the dimensionality has a certain influence on the detectability of the deep slip of the fault.
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jgg. 2022, 42(1): 65-70.
Using GAMIT/GLOBK software, we process the observation files of 37 AHCORS reference stations during Jan. 2013 and June 2018, and obtain the velocity fields of the stations under ITRF2008 and Eurasia frameworks. The error between the velocity field simulated by multi-scale spherical wavelet and the actual velocity field is less than 2 mm/a, indicating that this method effectively reflects crustal movement in this region. We use multiscale spherical wavelet to calculate and analyze the strain rates of the southern segment of the Tanlu fault zone and its surrounding areas. The results show that most of the areas west of the southern segment of the Tanlu fault zone are compressed, while most of the areas east of the Tanlu fault zone are dilatated in general. The abnormal variation of strain direction is located at the junction of plane expansion and plane compression. The maximum shear strain rate is symmetrically distributed along both sides of the southern segment of the Tanlu fault zone, and the northwest and southeast regions are high value regions with large strain accumulation and the possibility of earthquake, to which more attention should be paid. The southern segment of the Tanlu fault zone is mainly dextral strike-slip, there is tension in the north, the tensile component gradually decreases in the south, and the southernmost part turns into compression state.
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jgg. 2022, 42(1): 71-76.
Aiming at the complexity of seismogenic structure of the Nyima MW6.3 earthquake in Tibet on July 23, 2020 (no obvious surface rupture, the tendency of seismogenic fault is controversial), we obtain the coseismic deformation fields based on the ascending and descending orbit Sentinel-1A images. As a constraint, the seismogenic fault activity mode of this earthquake is discussed by setting two groups of possible fault slip models and combining with regional aftershock distribution and geological structure background. On this basis, the slip distribution characteristics of fault plane are further obtained. The results show that the seismogenic fault is a normal fault that dips to NWW located on the east side of the Yibug Caka graben, with a strike angle of 207°, dip angle of 33.1°, average slip angle of -89.27°, and dominated by dip slipping. The earthquake rupture is mainly concentrated at the depth of 5.4-9.3 km along the fault plane (unruptured to the surface), the maximum slip is approximately 1.7 m, and the moment magnitude is 6.3. The occurrence of this earthquake is the result of the current tectonic movement and deformation of the Qinghai-Tibet block.
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jgg. 2022, 42(1): 77-81.
Based on the nearest-neighbor distance algorithm, we analyze the clustering characteristics of small earthquakes in Jiaodong peninsula area using the mixture probability density function. The results show that: 1) The phenomenon of earthquake clustering is very obvious in this area, and the clustering rate has increased significantly in recent years. 2) b value decreased and clustering rate increased in Jiaodong peninsula area before the Rushan earthquake swarm and the Laizhou earthquake. Therefore, the coexistence of low b value and high clustering rate is a good predictor of seismicity in this area.
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jgg. 2022, 42(1): 82-87.
We adapt comprehensive geophysical means with seismic reflection as the main method and high density electrical method as the supplementary method and obtain relatively accurate detection results in the section from Yanguan to Lixian of the Lixian-Luojiabu fault. We summarize the abnormal response characteristics of wave impedance and electrical properties of faults in this region, especially the typical abnormal signs of ‘low resistance background and high resistance band’ presented by high-density electrical method, which make it possible to track faults in complex terrain by the high-density electrical method. Based on the results of geophysical exploration, we identify the shallow spatial combination mode of the fault zone, give the precise location of fault distribution, and gain a new understanding of the characteristics and distribution of shallow structure in the fault zone.
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jgg. 2022, 42(1): 88-95.
It is found that the anomalies of the double frequency (DF) microseisms in Xiangyang gravity station (XYS) before the Yingcheng MS4.9 earthquake on December 26, 2019 is continuously enhanced. By comparing the Ardhuin seismic spectra model(ASSM) and the western Pacific typhoon data, we find that the relationship between the enhancement anomalies of DF microseisms and the dominant frequency in the 10 hours before the earthquake and the western Pacific Phanfone are weaker than that of the local unknown near field homologous frequency signal. Combined with the observation and analysis of Enshi gravity station (ENS), we consider that the anomalies signal is not a slow earthquake event before the Yingcheng earthquake. 4 of the 5 earthquakes larger than MS4.0 in Badong-Zigui areas and Xiangyang-Guangji fault areas have the regularity of group activity with the earthquakes with MS4.5-5.0 near Qiyaoshan-Jinfoshan fault areas about 0.5-1 year ago. Further, their occurrence time are in the period of high noise level of DF microseisms from October to March in the next year. If the difference between the median and majority values of ENS-XYS DF microseisms baseline increases continuesly for 4 months or at a high level, it is possible to occur MS≥4.0 earthquake in the studied area. The conclusion of the anomalies before the earthquake can provide experience and reference for the occurrence period of earthquakes greater than MS4.0 near Badong-Zigui areas and Xiangfan-Guangji fault areas in the future.
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jgg. 2022, 42(1): 96-99.
Firstly,we derive the forward modeling formulae for third-order gradient tensor of gravitational potential caused by the finite cylinder. Then, the model experiment is carried out based on the theoretical formula, and two different approaches are utilized to verify the obtained analytic expressions. The first compares the results calculated by our proposed formulae and the central difference of gradient tensor of the gravitational potential. The second determines whether the sum of the components is zero acording to the Laplace equation.
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jgg. 2022, 42(1): 100-103.
Based on the observation data from the national gravity fundamental network, we use regularization methods to calculate the periodic terms parameters of LCR-G gravity meters, and analyze the adjustment results of the calculation. The results show that the regularization method can effectively screen the relative gravity periodic terms when the penalty factor is 80, and the changes in regularized parameter values have little effect on the periodic screening result; the amplitude of the periodic terms can reach more than 10×10-8 m/s2, which has a greater impact that reaches 10-8 m/s2 on the gravity value; the periodic of gravity meters will change with the observation environment or time, resulting in inconsistent solution results. As the periodic function model differs from the actual periodic changes, the model can only be approximate and cannot really simulate periodic changes.
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jgg. 2022, 42(1): 104-110.
In order to solve the problem of monitoring the uneven settlement of building structures in engineering, this paper takes the communication device as the basic theory and proposes a wireless static level system design based on LTE CAT-1, which is based on the embedded real-time operating system (FreeRTOS). The system is divided into three parts: data acquisition terminal, data base station, and client. The data collection terminal is mainly composed of pressure sensor, ZigBee terminal and Cortex-M3 microcontroller. We establish a number of data acquisition nodes using ZigBee. The data base station consists of a ZigBee coordinator, a Cortex-M3 microcontroller, a Wi-Fi module, and LTE Cat-1. The ZigBee coordinator collects data from multiple terminals. Users can view the data on-site by connecting the device Wi-Fi via PC or mobile terminal. The client is mainly designed for the quality inspection center or the personnel engaged in the municipal engineering industry, convenient to view the on-site test results and prevent the data from being untrue. The field test results show that the system can complete the collection and stable upload of settlement data, and the measurement accuracy reaches millimeter level.
