15 January 2019, Volume 39 Issue 1
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jgg. 2019, 39(1): 1-6.
In this paper, based on the relative positioning model of BDS/GPS single-frequency tight combination, we propose a combination algorithm of Kalman filter and particle filter to estimate the differential inter-system bias (DISB) of BDS/GPS tightly combined, and then analyze the algorithm performance by contrast with Kalman filter algorithm using short baseline data. The results show that the integer part of the phase DISB can affect the estimation of the DISB fractional part by changing the single-differenced ambiguity of pivot satellite. Further, the DISB of the proposed algorithm estimation corrects the tight combination and can improve the reliability of ambiguity resolution and fixed solution precision. Fixed solution precision can be increased by 10%~20%.
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jgg. 2019, 39(1): 7-12.
We build a new time-difference model for velocity estimation based on the existing time-differenced carrier phase technique. In the new model, time-differenced pseudorange observations are included. The static and kinematic data of Beidou navigation satellite system (BDS) is used to verify and analyze the improved method. The results show that the precision of the new time-differenced method could reach mm/s level in static conditions, equal to the GPS precision, and the accuracy of horizontal is better than the vertical. Furthermore, while in dynamic conditions, the mean square statistics of the velocity discrepancies between BDS time-differenced method and IE (inertial explorer) accord with cm/s, and the accuracy of the horizontal is better than the vertical.
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jgg. 2019, 39(1): 13-19.
Precise orbit and clock products for GPS, GLONASS, Galileo and Beidou from IGS MGEX and iGMAS are evaluated in this paper. Comparison among individual analysis centers (ACs), SLR validations, clock polynomial fitting and Allan deviation are utilized to analyze the characteristics of precise orbit and clock products from each ACs. The results show that: the orbit accuracy of GPS and GLONASS is about 1.0~1.3 cm and 2.0~3.6 cm, respectively; the GPS and GLONASS orbit products from iGMAS are better than other ACs’. For the Galileo system, the orbit agreement is about 10~17 cm in general; use of ECOM2 or a prior model can improve orbit quality. For the BDS system, the orbit agreement is about 21~40 cm for IGSOs, 11~18 cm for MEOs, and the radial accuracy is better than 10 cm and 5 cm respectively. However, GEO orbits have the worst agreements, having a few meters differences and radial errors of about 25 cm. Clock agreement is 0.2~0.4 ns for Galileo, 0.35~0.46 ns for BDS GEOs, 0.25~0.33 ns for BDS IGSOs, and 011~0.21 ns for BDS MEOs. The BDS IGSOs and MEOs’ clock products from CODE are markedly influenced by the yaw-attitude mode.
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Impact of GPS Antenna Phase Center Variations on Precise Orbit Determination of the GRACE Satellitesjgg. 2019, 39(1): 20-24.
We use onboard GPS data of GRACE satellites to research the impact of the priori phase center variations(PCV) model by ground calibration and in-flight PCV model, estimated by the residual method. The orbit accuracy is assessed by GFZ precision orbits comparison and SLR checkout. The results show that using prior PCV models can reduce orbit determination accuracy, but using in-flight PCV model can improve the orbit determination accuracy(mm level).
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jgg. 2019, 39(1): 25-30.
In this paper, we study Beidou sidereal filtering algorithm based on improved SSA. The embedding dimension is determined by phase space reconstitution Cao algorithm, and we propose an improvement for the shortcomings of Cao algorithm. Thus, the computational efficiency and accuracy of the SSA method are improved. The repetitive cycle characteristics of different constellation satellites of Beidou system are analyzed, and the repeat cycle of the Beidou multipath error is estimated to be 86 160 s. The results of Beidou short baseline solution are processed by sidereal filtering based on singular spectrum analysis method and traditional wavelet method. The results indicate that the effect of SSA multipath filtering method are better than the wavelet method, and the multipath error in original coordinate sequence can be eliminated well.
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jgg. 2019, 39(1): 31-35.
Aiming at the problem that the central node of the multi-quadric function fitting method is difficult to select, we introduce the method of the ant colony algorithm into the multi-quadric function and construct the high-precision fitting model with robust estimation.The ant colony algorithm is used to find feature points in complex terrain, and combines several non-feature points together as a central node in the construction model. Robustness is added to the multi-faceted function, and the effect of gross error on the fitting model is eliminated using the iterative method.GPS elevation fitting data processing example shows that the fitting method of multi-quadric function and robust estimation based on ant colony algorithm effectively eliminates the influence of gross error, fitting precision is improved by 26%.
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jgg. 2019, 39(1): 36-40.
To extract the features of 4-year GPS/PWV time series obtained by GAMIT/GLOBK software, we propose a GPS/PWV feature extraction method based on combination filter-assisted partly ensembled empirical mode decomposition(PEEMD) and Hilbert spectrum. First, filter-assisted PEEMD is combined with Hilbert spectrum to establish the feature extraction model of GPS/PWV. Then, the proposed method is applied to analyze the 4-year and 7-day GPS/PWV time series at TNML station, and the result of filter-assisted PEEMD is compared with the result of traditional wavelet decomposition. The results show that the proposed feature extraction method can accurately extract the feature components of annual and daily cycles, and that the results of the filter-assisted PEEMD are consistent with those of the wavelet decomposition, and that the extracted feature component are more coincident with the original signal.
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jgg. 2019, 39(1): 41-44.
The precipitable water vapor of stations in Xinjiang in 2016 is derived, according to the GPS data of the crustal movement observation network of China, combined with the pressure and temperature of the ERA-Interim model. The spatial distribution and seasonal variation of precipitable water vapor in this area are also analyzed. The results show the feasibility of GPS precipitable water vapor according to the comparison of radiosonde and GPS precipitable water vapor, which has a root mean square error of about 2.7 mm. Secondby, the annually averaged precipitable water vapor in Xinjiang is from 7.0 to 13.0 mm. Altitude is the main factor affecting the spatial distribution of GPS-derived precipitable water vapor; that is, precipitable water vapor decreases by about 1.4 mm for each kilometer increase of altitude. For regions at the same altitude, a region that is located at a lower latitude will have a higher content of precipitable water vapor. Thirdly, the seasonal variation of the precipitable water vapor is apparent. The precipitable water vapor is maximum in summer from 12.0 to 23.2 mm, the minimum is in winter, from 1.4 to 5.5 mm. The difference of precipitable water vapor between spring and autumn is quite small, and the changes are between summer and winter.
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jgg. 2019, 39(1): 45-50.
In non-equidistant GM(1,1) model there are constant terms without error and random terms with errors in the coefficient matrix. The errors of the coefficient matrix and observation vector are from the same source; the same elements are in the coefficient matrix and observation vector. These same elements ought to have the same corrected value. Therefore, a total least squares algorithm that is suitable to solve non-equidistant GM(1,1) model is deduced in this paper. The ill-posed problem in the non-equidistant GM(1,1) model is taken into consideration, which has an influence on the stability of the calculated results of total least squares. The method, which is to multiply the constant column in coefficient matrix by a constant, is proposed to alleviate the ill-posed problem.
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jgg. 2019, 39(1): 51-56.
In order to improve the cost model and convergence speed of the minimum norm unwrapping, we propose a two-dimensional global phase unwrapping method optimized with L0 norm. By analyzing the features of cost model in phase unwrapping with minimum norm, a cost function definition is employed in line with the L0 norm, which imposes a stronger constraint in the tangent direction of phase discontinuity boundary than that in normal direction. Meanwhile, to overcome slow convergence of low-frequency error compensation in linear equations, a data partitioning strategy is adopted in unwrapping processing, in view of the intrinsic independence of the minimum norm method, which only focuses on high-frequency information to improve efficiency in the iterative process, but processing of the low-frequency part is transferred to offsetting between data partitions. The experiment shows that reliability and efficiency of the proposed phase unwrapping method are enhanced.
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jgg. 2019, 39(1): 57-60.
This paper considers the problem of parameter fitting for polynomial models. Based on the theory of optimization method, we transform the problem into a constrained nonlinear programming problem, using the fastest descent method to iterate in the calculation to solve the nonlinear problems without linearization. Firstly, the rationality of the improvement of the external point method is illustrated by analysis of the penalty factor, the objective function, and the initial value of the external point method. Secondly, using an example we explain the feasibility of the method; compared with the traditional method, this method possesses high precision and multi-solution, and provides a new idea for studying the spatial data processing theory of nonlinear models.
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jgg. 2019, 39(1): 61-65.
In parameter solving under the conditions of coefficient matrix, the rational selection of regularization parameters and regularization matrix can improve the reliability of parameter estimation. The symmetric matrix is constructed by the eigenvectors corresponding to the smaller singular values of the matrix. The diagonal matrix is constructed by the main diagonal elements of the matrix, and then a new regularization matrix is obtained by combining with the unit matrix. The experimental results show that when the regularization parameter is less than 1, the parameter estimation of this algorithm is better than the ridge estimation.
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jgg. 2019, 39(1): 66-71.
Using nearly 70 000 gravity observation data, SRTM topographic data and GNSS/leveling control points data from Hunan and nearby districts, the EIGEN-6C4 global gravity fields model is taken to be the reference gravity field. And the Stokes-Helmert approach and spherical cap harmonic analysis are conducted to construct the 2′×2′ resolution Hunan GNSS gravity geoid model(HNGG2017). The precision test shows that the external error range is ±0.022 m. Compared to the historic model, the error of the new model in north areas such as Changde Hanshou and southwest areas such as Yongzhou Jiangyong are significantly reduced.
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jgg. 2019, 39(1): 72-76.
Based on measurement data of multiple faults in the middle Tianshan region since 2001, the current fault characteristics are analyzed from fault movement direction and fault average velocity. The results show that the activity of the fault alternates from positive to inverse, from left to right. Movement characteristics of the north Bugur-Qinggir fault is right, the activity is inverse. The activity of the F2 fault of Yamarik hill is inverse. The activity is highest in the F2 fault of Yamarik hill, and the Khorgos-Manas-Tugulu fault is the lowest in activity degree. The Khorgos-Manas-Tugulu fault, the north Bugur-Qinggir fault, and the F2 fault of the demon mountain are all in the vertical direction, and the first two horizontal directions are in the squeeze state. The time course of the fault activity rate has a stage characteristic, and the turning points of the fault have a good match in different periods.
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jgg. 2019, 39(1): 77-83.
In this paper, on-the-spot investigation and inspection is carried out for the fault deformation anomaly on Xiaguan site, northwest Yunnan province, and the original observation curves are analyzed. Furthermore, the accumulation of 3 parameters: the relatively horizontal torsion, the relatively horizontal movement and the relatively vertical variation of the fault, are calculated respectively; and the mechanism of deformation anomalies is discussed. The results are: (1) the observation position of the Xiaguan site is stable, the observation environment is good, there is no artificial disturbance or interference phenomenon, and the observation data is continuous and reliable; (2) the cross-fault observation of the Xiaguan site shows the fault has been being active as a right lateral slip, which has been enhanced recently; (3) there is a corresponding relationship between the abnormal compressional fluctuation of the fault deformation and strong earthquakes in the surrounding area; (4) the accumulation of horizontal compressional deformation from baselines across the fault shows that there is constant surface tensional fault activity. The accumulation of relative vertical deformation of the fault from leveling shows that the fault has a persistence of compressional fault (inverse) activities, and both can be explained under the mechanism of unity, which is of important reference value to explain the large number of contradictory phenomena in the observation of the cross-fault site.
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jgg. 2019, 39(1): 84-87.
In this paper, first we analyze the basic data of cross-fault flow deformation monitoring in the Shanxi area. There is a great monitoring blind spot, the monitoring site monitoring means is single, most of the sites are not arranged as rings, and there are a lot of bedrock mixed monitoring sites in the cross-fault flow deformation monitoring. Then, the monitoring effectiveness is evaluated from the aspects of monitoring environment and earthquake response efficiency. There are serious environmental interference factors in individual monitoring sites, seriously affecting the quality of monitoring data. Finally, the monitoring optimization of cross-fault flow deformation is discussed and some suggestions are put forward to improve the capability and level of cross-layer flow deformation monitoring in this area.
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jgg. 2019, 39(1): 88-92.
We apply a tomography method of first-arrival travel-time acquired from deep seismic reflection profile to explore the shallow P-wave velocity structure and the basement distributed shape of the southern margin of Taihang mountains. The results indicate a good corresponding relationship among the variations in P-wave velocity, the thickness of sedimentary cover, and the position of the faults. In order to probe the characteristics of active faults in the research area, two shallow seismic reflection profiles crossing the buried faults are carried out. The results show that Tangxi fault is a normal fault plunging towards the east, controlling the western boundary of the Tangyin graben. It is active during the middle Pleistocene. Tangdong fault is a west dipping fault, and is the main controlling boundary fault of the Tangyin graben. The latest activities can be traced to the early period of late Pleistocene.
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jgg. 2019, 39(1): 93-97.
This paper expounds the principle of the shear wave velocity method to evaluate the liquefaction of saturated sandy soil. Combined with a project example in Wuhan, the method is used to discriminant the liquefaction of sandy soil buried deeper than the application range of the ‘code method’ and the critical liquefaction depth of the field is determined on this basis. Compared with the dynamic triaxial test, the results of the identification of liquefaction and determination of the critical liquefaction depth are in good agreement, and it is proven that the liquefaction evaluation method based on shear wave velocity is feasible.
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jgg. 2019, 39(1): 98-102.
It is difficult to determine the penalty parameter and kernel function parameter of least square support vector regression(LSSVR). Additionally, artificial bee colony(ABC) is easy to fall into local optimum and its convergence speed is slow. So, we propose an improved artificial bee colony(IABC) to optimize the parameters of LSSVR and do research on deformation prediction. First, IABC generates positive and negative populations to increase the diversity of the initial group using the reverse learning strategy. After one iteration, information is exchanged between the optimal food sources of two populations to achieve optimal selection. Furthermore, we design an adaptive weight function and adaptive selection function to balance the exploration and development capacity of ABC. Second, we consider the predictive accuracy of LSSVR as the objective function, and transform it into the fitness function of IABC, thereby building a prediction model based on IABC optimization LSSVR. Then, taking the monitoring data of foundation pit as an example, we compare the prediction effect of the LSSVR model optimized by IABC, the LSSVR model optimized by ABC, and the combination model based on PSO. The results show that IABC increases the diversity of the population and improves the convergence accuracy. The prediction trend based on the IABC optimized LSSVR model is more practical and the prediction accuracy is higher than the contrast model.
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jgg. 2019, 39(1): 103-106.
We analyze the regression relation between the extensometer observation data from 2013 to 2016 and the cumulative precipitation. By calculating the M2 tide factor, we modify the extensometer observation during the rainfall, which plays an important role in eliminating rainfall disturbance anomalies.
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jgg. 2019, 39(1): 107-110.
Most of the integrated observation instruments of the seismic stations lack the function of automatic monitoring and alarming, so we propose a solution. We arrange the monitoring server in the seismic station, which can grasp the statistics from all the observing instruments. The multi-monitoring program employed in the server can search for unregular situations in the network and statistics, and at the same time send out the alarm to stations. The solutions are well proved in practice.
