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18 April 2011, Volume 31 Issue 1
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. 2011, 31(1): 1-4.On the basis of the absolute and relative gravity observations of the national major scientific project—China Crustal Movement Observation Network from 1998 to 2008，gravity field and its dynamic variations of Yushu earthquake are obtained, and the evolution characteristics of regional gravity field and its relation with the seismic activity before and after Yushu Ms7.1 earthquake occurred on April 14,2010 are studied in the sight of dynamics. The results show as follows. 1)The gravity change are closely related to GanziYushu active fault
i.e., the gravity observation can reflect material migration accompanying active fault and crustal tectonic activity well. 2)The dynamic variation images of gravity field reflect the anomalous informations of the gravity field observed with mobile survey with the development and occurrence of Yushu Ms7.1 earthquake clearly. 3)Temporal changes of gravity points nearby Yushu epicenter amount to more than 80×10 -8 ms -2 ,it reflected wavelike rises with gravity change before Yushu earthquake in time. -
. 2011, 31(1): 5-8.On the basis of negative dislocation model and PSO algorithm, the three dimension sliding rate of Longmenshan fault was inversed.
The inverted results indicate that the modern tectonic movement of the Longmenshan fault zone represents rightlateral thrust and small movement rate as a whole,but its movement has so obvious partition that main feature of the southern section is thrust, coupled with leftlateral and then it may be subjected to the effect of the Xianshuihe fault’s rapidly left-lateral slipping;in addition,along the fault from southern section to north, the
slipping movement has translated to rightlateral slip and the slideslip component has gradually increased. The northern and southern parts of the Longmenshan fault have taken on squeezing; otherwise the midsection shows a certain tension. It is inferred that the current tectonic feature of Longmenshan fault is concerned with the regional stress field and crustal structure in the context of the overall movement of QinghaiTibet Plateau. -
. 2011, 31(1): 9-14.
The technology of Computerized Ionospheric Tomography was used to reconstruct the distribution of electron density on UT9:00 from May 8th to May 10th, 2008 before Wenchuan Ms8.0 earthquake that occurred on May 12th.It is found that an ionospheric anomaly had taken place on May 9th, and the aspect about when and where this anomaly occurred is consistent with the conclusion made by VTEC analysis. After eliminating the possible impacts that space weather event existed in the ionosphere, we can undoubtedly maintain that the ionospheric anomaly on May 9th is a precursor of Wenchuan earthquake. Integrating all mentioned above, our study indicates that Computerized Ionospheric Tomography has great opportunities to be widely applied in the field of earthquake prediction.
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. 2011, 31(1): 15-18.According to the observations of 16 ultra-broadband seismometers from 1st to 12th May 2008, it is demonstrated that there were obvious anomalies in 64-512 s ahead of the Wenchuan Ms8.0 earthquake in some frequency exclusively from the impact of the typhoon, this
phenomena might be information related to the earthquake preparation. -
. 2011, 31(1): 19-23.With a gravity anomalies decomposition model, and through using the wavelet function “bior3.7” ,
the fourth order wavelet approximate components of the Bouger gravity anomalies of northeast margin of the QinghaiTibetan Plateau can be obtained.Furthermore,by utilizing the Bouger gravity anomalies come from the Moho and taking the information from the 6 artificial profiles as the initial control conditions,the crustal thickness of northeastern margin of the QinghaiTibetan Plateau is inversed, and the inversion results are analyzed and discussed according to the crustal thickness distribution features. -
. 2011, 31(1): 24-28.The relation between horizontal crust movement and the gravity change was studied and it is simulated that the spacial gravity change caused by the horizontal displacement of a crustal cuboid in a single direction is distributed in a negative symmetry.Being taken as an example, the distribution of the gravity change in the western China caused by the horizontal crustal movement and combining
with the GPS velocity field and DEM data was calculated,and then the results were compared with the gravity changes by satellite gravimetry and an explanation was given. -
. 2011, 31(1): 29-33.Taking the observation data of Zhangzhou station, Fujian as an example, we determined direction of the additional strain field in observation area from data of multicomponent borehole strainmeter. According to the characteristics of observation data, the dynamic strain field can be decomposed into the background strain field and the additional strain field. In order to study the variation characteristics of principal strain directions of the additional strain field, we used the formula of “lined borehole model” to calculate the vectors in principal strain directions. We also drew the vector trajectory diagram, and it is a clockwisely rotating ellipse. There was a phenomenon that the diagrams were more disordered and dispersed than the normal before the Ms 6.7 earthquake occurred in Gaoxiong, Taiwan, on March 4, 2010.
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. 2011, 31(1): 34-38.On the basis of the “casingcement sheathformation” system, the three dimensional finite element model was built.
With this model, and under the nonuniform stress conditions, the stress change characteristics before and after the borehole drilling were studied and the effects of the changes of the elastic modulus of the rock,cement and sonde casing, the Poisson ratio, the cement thickness and the expansion coefficient of the system on the component strain and plane strain after drilling were inquired as well. The results indicate that the influence incidence from the borehole drilling is probably 1.5 times as big as the aperture.
The influence of each parameter’s change on the strain is different, whereas the component strain response trend to the exterior load is primarily alike. Otherwise, under the uniform stress conditions, the effect of the cement thickness on the strain is related to the cement elastic modulus,but the plane strain is of negative correlation with the expansion coefficient -
. 2011, 31(1): 39-43.On the basis of detailed geomorphologic analysis of faulting profiles and deformed alluvial fans, etc. we suggest that the Enshi fault had been intensely active in Quaternary,it is characterized by dominant dipslip and partly dextral movement component and the displacement of the proluvium fans developed at the valley mouth of a gully.
The samples collected from the top of the proluvium fans were dated by Thermo luminescence to be 197.18±16.76 B.P. to 33.33±2.83 B. P.
The horizontal slip rate of the middle segment of Enshi fault is determined to be 0.43-0.5 mm/a, and the vertical slip rate is determined to be 0.07-0.17 mm/a. -
. 2011, 31(1): 44-48.The problem by over considered for geodetic data precision in most of the researches on crustal deformation and earthquake prediction is analyzed. The problem might let so conservative as to some valuable information in the data are not fully utilized. Pursuing high quality of the data is right, but the first consideration should be how to fully use the historic data according to the reality and the requirements, because the historic data are not replaceable. Thus, it should do the best for mining information from the data, and not give up the chance to get information from it only due to more deviation of the data. Finally, this viewpoint is further demonstrated with the results in an example, utilization and analysis of velocity field of crust vertical movement monitored by GPS in Chinese continent from 1999 to 2009.
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. 2011, 31(1): 49-54.The surveying technique and data processing method for axis determination of round normal section based on reflectorless distance measurement are discussed. A new train of though that is the calculation and comparison of the determined results from the simulative data of the center point of different elliptically scanning range based on geometric and algebraic distance is presented.Simulation and practical results show its feasibility and high efficiency.
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. 2011, 31(1): 55-58.Calculation for closing errors of simultaneous or asynchronous rings in GPS network is an important basis for checking the measurement accuracy. Searching for closed rings in the manual mode or with various commercial softwares has some flaws, can not find all of the independent closed rings. So, a new automatically searching algorithm for simultaneous or asynchronous rings based on Delauney triangulation is presented. The experiments show that the new algorithm can be used for calculating and checking rapidly and automaticlly the closing errors of all possible simultaneous or asynchronous rings in the GPS network.
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. 2011, 31(1): 59-62.Coordinate transformation parameters can be calculated from two sets of 3D points. Based on the characteristics of translation, rotation and zoom components of the transformation, the complete solution is divided into three steps. Firstly，positional vectors are regulated with respect to the centroid of sets of points in order to separate the translation component.Secondly,the scale coefficient and rotation matrix are derived from the regulated positions independently and correlations among transformation model parameters are analysed. It is indicated that this method is applicable to other sets of nonposition data to separate the respective attributions for transformation parameters.
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. 2011, 31(1): 63-67.The coordinate transformation between the geocentric celestial reference system(GCRS) and the international terrestrial reference system (ITRS) is one of the main questions for studying in astronomy / geodesy. In the coordinate conversion process based on Equinox, deduced the coordinate expression of instantaneous celestial intermediate pole (CIP) in GCRS is the basis for coordinate transformation based on nonrotating origin (NRO). According to the choice of Euler angles, the concepts of the celestial pole offset for the mean celestial pole at J2000 relative to GCRS and the equinox offset has been redefined. At the same time, the relationships between introduced various coordinate systems in the coordinate transformation models based on Equinox and NRO are given.
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. 2011, 31(1): 68-71.On the basis of the characteristics of GLONASS satellites,the scheme for analyzing the error of GLONASS broadcast ephemeris was discussed. By comparing with IAC’s precise ephemeris and clock products, the performance of GLONASS orbit and clock error in broadcast ephemeris for all healthy GLONASS satellites in a period of 2 weeks were analyzed. The results show that the RMS of radial orbit error of current GLONASS broadcast ephemeris is less than 1 meter, the tangential one is less than 6 meters and the normal one is less than 4 meters. The RMS of GLONASS clock error in broadcast ephemeris is less than 15 nanoseconds. From the analysis of signalinspace range error, the whole accuracy of GLONASS satellites broadcast ephemeris is better than 4.5 meters.
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. 2011, 31(1): 72-77.The accuracy of moving carrier’s velocity, which was determined by GPS, depends on mainly accuracy of carrier phaserate. It is difficult to guarantee accuracy of velocity with raw Doppler and differential phase. Carrier phaserate estimated from Kalman filter was adopted to determine the velocity instead of Doppler. The model and theory of differential velocity measurement and carrier phaserate estimated by Kalman filter were introduced.The flight data of a certain airborne gravimetry were calculated with Kalman filter method, and the results were compared with those from GT1A and WAYPoint. It is indicated that GPS carrier phaserate estimated from Kalman filter can be adapted to some highvelocity and more complicated movements, its accuracy of velocity measurement can achieve at mm/s level, the result approaches to that by GT1A and is higher than that with WAYPoint.
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. 2011, 31(1): 78-82.The outlier detection methods in satellite gravity gradiometry including threshold method, Grubbs’s test, Dixon test, wavelet method and combined method are studied.On the basis of the the origin and properties of satellite gravity gradiometry outliers, the gravity gradiometry dataset with outlier are simulated. The results indicate the combination of Dixon test and wavelet method is the most efficient algorithm.
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. 2011, 31(1): 83-86.In order to solve various types of coordinates amendment problems of monitor stations in satellite navigation system, it is necessary to accurately give the change rate of the position for each ground station caused by the plate movement. The measured velocity fields
computed from GPS observation data of China Crustal Movement Observation Network was adopted, and established virtual local plate motion model by using sliding Euler vector modeling, accuracy analysis shows that the result in the eastwest direction has the accuracy of 2.092 mm / a, in the northsouth direction has the accuracy of 2.072 mm / a, in sparsely distributing areas and border of China, the accuracies are not significantly reduced. So the model can be used to amend the coordinates of various types of ground stations in China’s satellite navigation system. -
. 2011, 31(1): 87-90.On the basis of the relationship between gravity difference and scale parameters in linear term of relative gravimeter, a method to detect the change of parameters in linear term has been developed, and the change of parameters in linear term of G793 and G854 gravimeter were studied from the gravity data of western Yunnan area from1989 to 1996. The results show that the change of parameters in linear term of relative gravimeter can be calculated with high precision, and the method is reliable for detecting noticeable changes of parameters in linear term of relative gravimeter.
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. 2011, 31(1): 91-95.Aiming at selection of frame sites, combination of global Hfiles and selection of parameters of similarity transformation, four calculation schemes are designed to process the observations of regional GNSS net in large, medium and small scale . On the basis of these solutions, the differences shown as follows between results under different calculation schemes are analyzed.
As far as all levels of regional net are concerned, if combined with global Hfiles and similarity transformation is invoked successfully, the difference between the results under scheme which selects whole frame sites of IGS05 and which selects a part uniformly is not significant. For large regional GNSS net, the scheme combined with global Hfiles gets different result from the scheme which doesn’t be combine, with a maximum up to 4 mm/a in the horizontal velocity of ITRF2005. As for medium and small regional GNSS net, the difference of relative velocity field between the results of scheme which combines with global Hfiles and which not is in significant. -
. 2011, 31(1): 95-99.The estimations of precise satellite clock difference with nondifference model and the epoch differential model were studied, and the characteristics of the two models were compared through analyzing the computing speed and precision. Test results show that the estimate based on zerodifferential model has high precision and high reliability, more observation information can be used, and the ambiguity fixing also can be realized,but it needs more unknown parameters, the computing speed is slow, and the high resultant precision needs a converging produce gradually. While with the epoch differential model, the estimate needs less unknown parameters, the efficiency of computation is high, and the precision doesn’t need the converging produce, but compared with nondifference model its precision is lower, and the initial value should be extracted from the navigation messages or obtained through other ways. The systematical biases caused in that way will be absorbed by the ambiguity and receiver’s clock error and it won’t influence the final positioning results.
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. 2011, 31(1): 100-104.
With respect to high speed acquisition system, the band of power line interference is extreme narrow.
In the design of power line interference filter with traditional IIR and FIR methods,there is a need of a high order filter of favorable attenuation characteristics, it is hard for hardware and software to realize. Considering the wide frequency bandwidth of seismic electromagnetic radiation pulse, high sampling rate in the observation system and the characteristic of TMS320C6416, an improved algorithm of frequency domain filtering is presented. This algorithm has the advantages of simple principle and less time consuming by theoretical proof and is helpful to realize the signal reconstruction perfectly. The simulation results have proved the effectiveness of the algorithm. -
DATA PREPROCESSING ALGORITHM OF SATELLITE LASERRANGING BASED ON CURVE RECOGNITION FROM POINTS CLOUD. 2011, 31(1): 105-108.In order to solve the preprocessing algorithm of SLR data, the SLR data from the COMPASS quality is analyzed. The difference between curve recognition in the fields of reverse engineering with computer vision and preprocessing algorithm of SLR data is discussed, and then a new algorithm of satellite laser ranging data preprocessing based on curve recognition from points cloud is proposed. This algorithm treats SLR data processing as a problem of curve recognition with organized points. The algorithm is checked by using the SLR data from the COMPASS. The results show that the rate of accordance between results of the new proposed method and the screen displaying method can reach 85% or higher. Accordingly, the new method can be used for SLR processing data automatically and meet the need
in building the navigation system. -
. 2011, 31(1): 109-112.The Kalman filtering method of the state transition matrix for the random matrix is discussed, specific filtering algorithms is given, and the convergence characteristics of filter and the range of parameters are analyzed. Finally, the effectiveness of this filtering method is confirmed by a practical example.
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. 2011, 31(1): 113-116.There are two factors: affecting the accuracy of GPS height transformation based on quasigeoid model, the geodetic height accuracy and interpolated height anomaly accuracy.On the basis of the simulation and practical quasigeoid models, the effect and accuracy of GPS height anomaly interpolation are analyzed with four methods, including inverse distance interpolation, linear interpolation, Shepard interpolation and Chebyshev interpolation, the results show that the Chebyshev interpolation method is accurate and stable for the high resolution quasigeoid model.
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. 2011, 31(1): 117-122.Through the research for the rules of storing entity data in the DXF, achieving that the direct operating of DXF file to complete maps conversion without the CAD support is achieved and
the corresponding graphics conversion program has been compiled with specific projects. After test, with this program we can complete map conversion between National Coordinates, National Coordinate and Local Coordinate, Local Coordinates, and we have achieved integrated blocks conversion in the conversion process. -
. 2011, 31(1): 123-126.On the basis of comparison among variant image output formats, we preferred CGM as the image output format for the preprocessing software of data collection of “Compatible seismograph system for recording reflection/refraction wave”. In the same time, we have developed a general plotting library for CGM image output. The method of general plotting library combined with dynamic link library technique can resolve the problems in different softwares. Finally we obtain the output of interpreting results of deep seismic reflection/refraction sounding data.
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. 2011, 31(1): 127-131.Gravity anomaly data are commonly used in the gravity aided inertial navigation simulations. The study on the ability of the gravity gradient to aid an inertial navigation system, however, is lacking.Simulations of multiple routes in the same area with SITAN algorithm have been conducted based on the gravity anomaly and vertical gradient of gravity data. Statistical analysis indicates that the initial localization and matching aided navigation results are better from the vertical gradient of gravity data than those from the gravity anomaly data.
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. 2011, 31(1): 132-137.Downward continuation is one of the indispensible steps in preprocessing satellite gravity gradient data when recovering the earth gravity field with spacewise method. The spherical interior Dirichlet method, the Poisson integral iteration method and the spectral method, which are used in the processing of aerial gravity data, are introduced into the downward continuation of satellite gravity gradient data, the corresponding mathematical models are constructed, the numerical value inconsistency in the traditional spherical interior Dirichlet problem is also solved, and the downward continuation effects of these three methods are analyzed and discussed by taking the simulated satellite gravity gradient data as the example. The results show that when the continuation distance is 5 km, the resultant continuation precision of the spectral method is the best, the spherical interior Dirichlet methods’ is the second, and the Poisson integral iteration methods’ is the last; when the continuation distance is 250 km, the resultant continuation precision of the Poisson integral iteration method is the best, the spectral methods’ is the second, and the spherical interior Dirichlet methods’ is the last.
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. 2011, 31(1): 138-141.The basic problem and the processing strategy about precise orbit determination of GPS navigation constellation were studied.From the observations of 148 IGS stations from March 29 to April 07 in 2008, oneday and threeday orbit solutions of GPS navigation constellation were determined. In order to evaluate the accuracy of the orbit, the orbit was compared with final orbit products produced by CODE. The results show that using this strategy, the oneday orbit solutions accuracy is better than 6cm in radical direction, while threeday orbit solutions accuracy is better than 5 cm in radical direction.
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. 2011, 31(1): 142-146.The radar signal propagation delay caused by atmospheric effects, especially atmospheric water vapor content changing in time and space, is one of the main error sources in repeatpass interferometry SAR, which is difficult to eliminate and greatly limits the applications of differential interferometry SAR. When only GPS water vapor is considered for the atmospheric delay correction in InSAR, it is will be leading to poor effect of correction taking into account the impact of topography to atmospheric wet delay.
The relationship between the terrain and vertical layered component of atmospheric wet delay was analyzed and a function model between them was established. On the basis of it, a new interpolation method is proposed, which takes into account the impact of terrain on atmospheric delay. The calculation results show that the new interpolation method has obvious advantages compared with IDW and Kriging methods. -
. 2011, 31(1): 147-151.To solve the IF signal capture problems in the software GPS receiver, first the parallel code acquisition algorithm based on FFT is used to achieve the coarse frequency of IF signal and obtain the fine frequency based on the use of FFT in frequency domain analysis.The acquisition decision is dependent on the ratio of the maximum peak and the subpeak ratio,at the same time,the specific steps are presented. Through the analysis of the real GPS IF signal, experimental results show that the FFTbased GPS signal acqusition and FFT frequencydomain method are very effective to obtain the fine frequency,this is,can capture quickly and accurately,so to meet the requirements of GPS software receiver.
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. 2011, 31(1): 152-155.The standard is the basis of a product for manufacture,calibration and use. The consistency of relevant standards which are applied in those fields of the invar staff is researched. The study demonstrates that the parameters in national standards for calibration and use are much different from those in international standards for manufacture.
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. 2011, 31(1): 156-159.Through studing the existing theory and method of database quality control, the characteristics of urban engineering geology database are analyzed, and the knowledge rule set facing urban engineering geology database is established based on diging the topological consistency of spatial data and the logical consistency of attribute data, and then, the technical methodology of the quality control of urban engineering geology database based on the knowledge rule set is proposed. Finally, with this quality control method, the test on urban engineering geology database of Nanjing is carried out, and the correctness and the validity of this method are proved.
