Home Table of Contents
13 June 2012, Volume 32 Issue 2
-
Select all|
-
. 2012, 32(2): 1-6.Seeing that there are still many factors governing the accuracy of InSAR although they have appeared to good application in various field as earthquake, landslide,etc. this paper focus on the two sources of errors controlling the accuracy of InSAR.In the first place, theoretical analysis has been first made for the evaluation of influence of baseline and terrains errors on surface deformation.On the basis of above theoretical analysis, we estimated the influence of baseline errors and terrain errors on InSAR for ALOS PALSAR radar images without accurate orbit information. The spatial patterns of additional surface deformation due to the two error sources have also been retrieved. The results show that the orbit accuracy of ALOS PALSAR is 3-5 m, in which the displacements must be rectified for the low orbit accuracy.The simulation and experimentation all show that baseline is main error sources in the use of ALOS PALSAR and terrain errors is negligible. For
the accuracy of better than 1 cm in deformation measurements, the length of baseline must be less than 400 m under current SRTM DEM if twopass interferometry was used. -
. 2012, 32(2): 7-10.We collected and combined all mobile GPS data between 1999 and 2009 around ZhangjiakouBohai seismic belt, and obtained the velocities at 143 stations. At the same time,we constructed a regional strain field of the ZhangjiakouBohai seismic belt region with leastsquare collocation, and investigated the slip rate of ZhangjiakouBohai belt. The study results show that: 1) the regional maximum displacement is about 5 mm/a,2) ZhangjiakouBohai seismic belt is creeping in with leftlateral slip rate of 2.0 mm/a and the creeping depth is in a range of 25-45 km,3) The maximum shear strain is 3×10 -8 /a in BeijingTianjin and Tangshan area.
-
. 2012, 32(2): 11-15.Using the GPS velocity field data from 1999-2001,2001-2004 and 2004-2007 on short time scales, we studied the overall motion characteristics of Xiaojiang fault through linear model of block(RELSM), and reached the result that its average leftlateral slip rate is about 3.0~7.1 mm/a.According to the segmentation of surface rupture of fault due to historical earthquakes, we
analyze the different characteristics of spacetime of strain accumulation on every fragment by using the method of GPS velocity profile. The results indicated as follows. 1)The sections in different time periods of Xiaojiang fault have better consistency on relative motion and deformation mode, are sinistral strikeslip and pullapart movement characteristics.2)RELSM results show segment difference and decrease of slip rate from north to south.3)Strain accumulation features show, the northern section above middle north section,middle south section and the southern section are not conducive to the accumulation or low levels of it.4)The northern section of Xiaojiang fault zone is abnormal regions which was relatively closed and there was high rate of shear strain accumulation. -
. 2012, 32(2): 16-19.On the basis of 1970—2006 leveling observations, we obtain the vertical velocity field of the west Qinling tectonic belt with the method of the least square adjustment.The results show that Liupanshan and its surrounding areas are rising with the rate 2-3 mm/a relative to Baoji benchmark(Longbao17) and the nearby Lanzhou basin area shows a subsidence trend, with the average rate 1.5 mm/a.
-
. 2012, 32(2): 20-23.The highrate GPS data from 8 stations in the 2011 Mw9.0 Tohoku earthquake were processed by using precise point positioning, and the displacement time series at each GPS site were analyzed to derive displacement waveforms for this event. The results indicate that the maximum displacement of GPS stations during the earthquake is larger than the permanent deformation. The kinematic solutions show that the maximum amplitude of east and north displacement is up to 5.9 m, 1.8 m respectively, and horizontal displacements were towards the epicenter on the whole. At last, the epicenter and the S wave velocity is derived from the arrival time recorded by the GPS stations in the region.
-
. 2012, 32(2): 24-27.In order to validate the accuracy and the performance of the LaCoste & Romberg (LCRⅡ), a concurrent flight test over
a mountain area was undertaken.The LCR gravimeter Ⅱ and an LCR gravimeter Ⅰ system side by side. The results of the flight test show that the standard deviation of the gravity anomalies difference measured with the two systems is about 4.0×10 -5 ms -2 namely the accuracy of the single system is about 2.8×10 -5 ms -2 if we assumed the two systems have the same accuracy. They also indicate that the standard deviation of the 5′×5′ grid mean gravity anomalies difference from the two systems is about 4.9×10 -5 ms -2 namely the related accuracy of the single system is about 3.5×10 -5 ms -2 and 2.9×10 -5 ms -2 after two outliers
were eliminated. In general, LCR gravimeter Ⅱ system has the identical accuracy as the LCR gravimeter Ⅰ system, but it can be quickly leveling off. -
. 2012, 32(2): 28-31.We present a method to realize viscoelastic boundary condition in ANSYS finite element software by using the Combin 14 element.The numerical results show that the method can well absorb the boundary reflection wave,and is insensitive to change of boundary normal stiffness parameters while the tangential stiffness parameters keep constant,and vice versa.The results also verify the effectiveness and stability of the method.
-
. 2012, 32(2): 32-38.We computed and compared the vertical loading deformation from GPS and GRACE and found that at most global sites, the root mean square (RMS）of GPS coordinate time series decreased after removing the GRACE estimates, and the annual variations of the GPS height at most sites also agree well with GRACE or geophysical model estimates in the amplitude and phase.It indicates that the nonlinear seasonal GPS vertical variation is mainly caused by the geophysical loads. However, at some sites, particularly in the Antarctica, some ocean coasts and small peninsulas, large discrepancy has been found between the estimates with the two techniques. We analyzed and discussed the error sources of the discrepancies between GPS and GRACE and their effects,
which is proved by a good agreement with geophysical models, and the remaining disagreement may be due to the GPS technical errors. It needs to further investigate using longer and more GPS and GRACE measurements. -
. 2012, 32(2): 39-43.By use of the monthly average gravity model,from Jan. 2003 to Dec. 2010, released by GRACE datacenter CSR,we obtain the variation of continental water storage in China, then analyse and explaint the results with meteorological and hydrological information. The research suggests that the variation of water storage from GRACE is in good agreement with reality,and reflects well the severe drought in southwest provinces from Sep. 2009 to Apr.2010.
-
. 2012, 32(2): 44-46.Using the RBF(Radial Basis Function) neural network to interpolate the GPS satellite coordinate computed by broadcast ephemeris was proposed in order to solve the problem of Runge Phenomenon(RP) in polynomial interpolation. The GPS satellite coordinate calculated by GPS broadcast ephemeris in 25th, July 2011 were selected to test the RBF neural network interpolation method. The interpolation results compared with the GPS satellite coordinate calculated by direct computation method show that RBF neural network interpolation method can avoid the RP, improve the interpolation stability and accuracy as well meet the demands for GPS point positioning.
-
. 2012, 32(2): 47-50.Oneday, threeday and sevenday orbit solutions of GPS navigation constellation based on the observations of IGS stations in different numbers and geometries from 87day to 95day in 2008 were determined. The final solutions were compared with IGS precise ephemeris. The result shows that the accuracy of oneday, threeday and sevenday orbit solutions could reach up to 4.9 cm, 3.6 cm and 3.4 cm when optimal geometry of the 40 IGS stations are selected. With the increase of IGS stations, the orbit accuracy could not be remarkably improved when the IGS stations have reached a certain limit, but computing time become longer. Thus it is evident that the geometry is the key factor which affects the accuracy of the final solution when the number of IGS stations is fixed.
-
. 2012, 32(2): 51-54.With the view of influence analysis, a new Bayesian method for gross errors detection based on divergence of KullbackLeiber is proposed. Under the condition of unequal weight and independent observations, a comparison among the data deletion model, the variance inflation model and the mean shift model based on certain prior distribution is made, and the computational formula of divergence of KullbackLeiber about the three models is given and a judge rule of gross error detection is established. Finally, the method is used for gross error detection in triangulateration network and a good result is obtained.
-
. 2012, 32(2): 55-59.The latest version of international reference ionosphere, updating contents and data sources are introduced. The construction and functions of international reference ionosphere source program is elaborated. Interface routine based on source program
is achieved for computing ionosphere electron density and other parameters.By use of international reference ionosphere for the
features of ionosphere electron density.It is able to express electron density’s variation with time, equatorial anomaly and winter anomaly.
It’s highly reliable for computing TEC of middle latitude area. Also, discrepancies between international reference ionosphere model value and data of digital ionosondes are analyzed on different latitude and different geomagnetic conditions which can provide reference for application of international reference ionosphere in China regional ionosphere. -
. 2012, 32(2): 60-63.Gross error detection is one of the important data processing steps of mountainous LIDAR point cloud data. Through analysing the features of gross error distribution,original LIDAR point cloud data can be divided into extreme outliers, outlier clusters and isolated points. On this basis, the idea of hierarchical gross error detection of mountainous LIDAR point cloud data is proposed, and an example of experimental data is verified. Experimental results show that the method can effectively remove gross errors from original mountainous LIDAR point cloud data, and, to a certain extent, improving the effect of preprocessing of point cloud.
-
. 2012, 32(2): 64-68.The parallel algorithm based on supercomputer for solving the Earth’s gravity field model was investigated.Shared and distributed parallel environment (OpenMP & MPI) applying to the least squares method are analysed and compared. Different threads, different node to determine the gravity field model at different levels of time consumption and efficiency are compared with each other.
-
. 2012, 32(2): 69-73.Aiming at the defect of singlefrequency GPS receiver affected by ionospheric, the effect of ionospheric delay correction with four kinds of different ionospheric models (i.e. Klobuchar, NeQuick, IRI and IGGSH) have been analyzed by use of some GPS data as the example. The spatialtemporal characteristics of each ionospheric model is analyzed statistically.The calculation results show that IGGSH model is better than the other three ionospheric delay correction models.
-
. 2012, 32(2): 74-77.]Indoor positioning by the use of wireless sensor networks is a hot topic for research. The traditional ranging positioning method based on the strength of received signals can not work in complex and dynamic environment because the necessary priori ranging model parameters of the positioning scene can only be obtained through artificial modeling. The current research based on the analysis of ranging models, by attaching different path loss exponents to each reference node through the communication between the reference nodes, achieves the selfadaptation and automation of indoor positioning. The experimental results show that the positioning accuracy is improved with this algorithm compared to the method through single model parameters.
-
. 2012, 32(2): 78-81.Automatic real-time guidance measurement is the key to modern construction measurement. Nowadays,in China the new underground 3D traffic engineering method of pipe replaced by box culvert jacking is used, but the manual measurement can not meet the requirement of realtime monitoring.So a set of Total Stationbased intelligent automatic guidance system has been developed thus could achieve the measurement automatically and improve work efficiency greatly. The principle and key technology of this intelligent guidance system is introduced.In the same time,combined with successful application of culvert jacking highway in the existing railway project in Shanghai Jinshan, this system proved practical and excellent with higher reliability and accuracy.
-
. 2012, 32(2): 86-90.Taking the data of China geoid datum in consecutive days,as an example,the latest International Terrestrial Reference Frame(ITRF2008) was used to analyzed the difference between ITRF2008 ,ITRF2005 and CGCS2000. It is valuble maintaince to China geoid datum. It is concluded that the ITRF2008 more precise than the previous ITRF models, but there are some differences, which is related with observation stations, plate, the strategy for data solving and other factors. The
nonuniforming and complexity of the earth plate movements cause the CGCS2000’s changes which should be dynamicly maintained.In the same time,the transformation scheme between CGCS2000 and ITRF2008 is preliminarily described. -
. 2012, 32(2): 91-95.The tropospheric delay is the main error for GNSS navigation and positioning.Along with the accuracy improved and deep research, the UNB3m,EGNOS,SHAO,etc. tropospheric models were proposed in recent years.
Three IGS stations are used to analyzed the accuracy of these models. The results offer some valuable information for COMPASS navigation users. -
. 2012, 32(2): 96-99.The thirdorder GPS geodetic network is a longterm construction project of national basic surveying. Making full use of advanced GPS reference points of all kind of project can not only improve the accuracy but also accelerate the construction of the thirdorder GPS geodetic network. The calculating method based on advanced GPS reference points for the thirdorder GPS geodetic network is introduced and the data of an area is used as an example.
-
. 2012, 32(2): 100-104.The zenith tropospheric delay (ZTD) and zenith wet delay (ZWD) derived from the European Center for MediumRange Weather Forecasts data (ECMWF ZTD/ZWD) were assessed by calculating ZTD/ZWD from GPS observations, and the calculation method was also discussed. The results show that the bias and rms for the ECMWF ZTD are about -1 cm and 2 cm respectively, the absolute values of which for ECMWF ZWD at BJFS and LHAS sites are 1 cm and 1.6 cm respectively.
-
. 2012, 32(2): 105-109.After explaining the method and models for Precise Point Positioning (PPP) based on combined GPS and GLONASS, the positioning accuracy of static and kinematic PPP and convergence of kinematic PPP for GPS, GLONASS and their combination were compared with each other by using the data processing software developed by the author. The PPP of numerical results show that: GPS, GLONASS and their combination have access to centimeterlevel static and kinematic positioning accuracy, but the last is better than the former two in statistical accuracy and the GPS/GLONASS combination can improve the convergence speed of kinematic PPP, particularly prominent for
the case of less observed GPS satellite. -
. 2012, 32(2): 110-114.The main task of network adjustment of airborne gravimetry is to compensate systemic errors. In order to weaken the influence of outliers and improve the effect of compensation, this paper brings in thresholding and robust estimation, and confirms these two methods’ validity and reliability in simulated data processing. By means of comparison，a conclusion is reached that the robust estimation has more practical value in the network adjustment of airborne gravimetry.
-
. 2012, 32(2): 115-119.According to the spectrum characteristic of the horizontal acceleration correction in the aerial gravity measurement and the partition rules of wavelet transformation frequency band, the wavelet prefilter scale of the horizontal acceleration correction is deduced.
On the basis of the correlation among the wavelet transform scales of the signal, as an example,some surveying data were preprocessed by Haar wavelet、db4 wavelet、db6 wavelet and sym6 wavelet, and the results are compared with the results from FIR low pass filter in common use. The comparison shows that the precision of the wavelet prefilter is higher than the FIR low pass filter in the preprocessing of the horizontal acceleration correction and it is more symmetrical as preprocessed by db serial wavelets.Thus it is proposed that the Daubechies wavelets or the sym8 wavelet with much longer branch are more useful in the preprocessing of the horizontal acceleration correction. -
. 2012, 32(2): 120-123.The different coordinate systems mean different geophysical concept.In the geodetic network the local deformation and accumulation error exist, and there are stochastic value in the common points with the different coordinate. So the coordinate transformation from low precise coordinate frame to the high one can not approve a high precise reference frame after this transformation. A combined method based on variance component estimation using similarity transformation and regressive approximating is presented.For the local error accumulation and distortion and the stochastic value of the common points, the accuracy of coordinate system is improved after the transformation
with the combined method from Xi’an Geodetic Coordinate System 1980(XAS80) to China Geodetic Coordinate System 2000 (CGCS2000). -
. 2012, 32(2): 124-127.As to GPS station coordinate residuals, we used two classical ARMA modeling methods (BoxJenkins method and PanditWu method) to fit the GPS station coordinate residuals, and made comparative study. According to the experiment, we found out that the two methods have a little difference while there is abundant data. If the data is poor, with the PanditWu method the results will be better.The amplitude of residuals reduces about 1/3 and the distribution is more uniform.
-
. 2012, 32(2): 128-133.Wavelet transform has played an important role in the field of surveying data processing,as the noise can be eliminated effectively on the basis of wavelet decomposition and reconstruction. Currently, the research of wavelet denoising mainly focuses on the development of wavelet denoising methods,however, the validity assessment of wavelet denoising result should be indeed taken into account.
Seeing that, a comparative study on validity assessment methods of wavelet denoising is down. The practical performance of existing validity assessment methods is obtained through a series of experiments. -
. 2012, 32(2): 134-138.Aiming at optimal construction of pseudolites in GNSS/Pseudolites(PLs) combined system, this paper pointed out the necessity of PLs’ joining in GNSS,and built a fourdimensional(4D) model based on azimuth angel, elevation angel and observed epochs.Then, an experiment was taken to test the model,and the results show that the increasing number of visible satellites and the changing information of lowelevation satellites can enhance the reliability of the system and improve positioning accuracy.Panorama shows that variations of the PDOP value and the reliability value within the optimal region are similar but the distributions are different.The
weight constrained by the PDOP, internal reliability, cost and other factors can be effective coordinate indexes for selecting optimal system and provide reliable basis for effectively solving the problem of locating PLs for GNSS/PLs optimization.\ -
. 2012, 32(2): 139-142.Restricted by the observing conditions, some important data of GPS elevation fitting are often missed
or not enough. Using conventional methods will reduce the fitting accuracy of the quasigeoid.By use of the EM algorithm with the addition of “potential data” , conditional expectation of the missing data,it can effectively improve the accuracy of GPS elevation fitting for lack of data. -
. 2012, 32(2): 143-147.With the developments of satellite, radio communication, and computer technology, autonomous operation of satellite navigation system becomes more and more important. Inter-satellite Link (ISL) is a key technology. The Walker constellation structure, and its categories, frequencies and rules of intersatellite links are introduced.Besides, the construction method and visibility of intersatellite links of Walker constellation are analyzed and then, the azimuth, elevation, and range are computed as well. Study shows that multiple ISLs can be built in Walker constellation.
-
. 2012, 32(2): 148-154.This method based on image’s gray to detect the interest pointis mainly includes Moravec operator, Harris operator, Forstner operator and the improved Forstner operator nowadays, and there are some differences in the detect speed, positioning accuracy, stability between different operators. In this paper the detect speed, positioning accuracy, stability and parameters’ suitability of each operator are evaluated by testing a artificial test image and a really taken image, and the test results show the advantages and disadvantages of each operator. A improved operator is proposed based on the test results. The study results show that the improved operator has the characteristics of strong stability, high positioning accuracy and autosetted threshold.
-
. 2012, 32(2): 155-159.The method of coupling coefficients inversion for 4component borehole strainmeters was studied, which adopts two computation models including azimuth correction and phase lag effect. Using the data from the network of 4component borehole strain observation during the Tenth FiveYear Project of China, the calculation results show that coupling coefficients inverted with the two models are close to each other in most sites, and the results of phase lag, azimuth correction and simulation residual are relatively stable. However, some sites’ results of phase lag are different obviously, which results in great difference between coupling coefficients inverted with the two models. On the basis of faults distribution of sites’ surroundings, the physical mechanisms that possibly lead to the difference are discussed.
