2012 Vol. 37, No. 12
A Mw 9.0 earthquake occurred in the Tohoku-Oki of Japan in 2011.The coseismal deformation observation from GPS and InSAR meanings were used to inverse the slip distribution of the earthquake.Firstly,six ascending ALOS/PALSAR tracks and three descending Envisat/ASAR tracks that cover most of northeastern Japan were processing by two-pass interferometric synthetic aperture radar(InSAR) to obtain acoseismic deformation results,which are calibrated by GPS data.Secondly,the rectangle dislocation models in elastic half-space were used to derive the kinematic characteristic of the earthquake fault combining with GPS and InSAR data.The inversion result indicates that the fault slip concentrates mainly in the depth between 40 km and 50 km,the maximum slip is about 50.3 m,the geodetic moment is 3.197×1022 N·m(Mw 8.94).
Outlier detection is one of the key processes to data preprocessing of satellite gravity gradiometry(SGG),and its objective is to obtain high quality SGG data.The performance of thresholding,Dixon test and wavelet algorithm was discussed in the outlier detection of SGG data.And two combined schemes were presented to overcome some deficiencies of these three methods,namely the combination of Dixon test and wavelet algorithm,and that of Dixon test,thresholding and wavelet algorithm.The simulation results show that both the two combined schemes can improve the quality of outlier detection effectively.
Aiming at the deficiency of single effect quantity analysis method of high arch dam safety monitoring,we introduce a data fusion theory named D-S evidence theory into multi-effect quantity fusion model of high arch dam.A new formula for calculating the fusion coefficient is put forward suitable for D-S evidence fusion evaluation to high arch dam safety,and a multi-effect quantity fusion model of high arch dam is established based on improved D-S evidence theory.The results of engineering example indicates that this method is reasonable and feasible,which not only provide a new way for high arch dam multi-effect quantity comprehensive evaluation,but also can reduce uncertainty and unacknowledged in high arch dam safety evaluation.
GPS data from Shanxi Continuously Operating Reference Stations(CORS) during the period of 2009-05 and 2011-02 were processed using GAMIT/GLOBK software.Then coordinate time series and velocities of the reference stations were determined.Based on it,crustal movement of the Shanxi Province was analyzed in detail.Results show that the absolute horizontal velocity of the stations inside this region move at 33.97 mm·a-1 on average in the direction of SEE110.55° under the ITRF2005 reference frame,while the average horizontal velocity relative to the Eura-Plate is 6 mm·a-1 in the direction of SE130.69°.As for the vertical velocity field under the ITRF2005 frame,subsidence behavior is shown in most areas.Moreover,stations in the southern part subside at a higher rate than those in the north.Main cause of the subsidence is due to the long-term exploitation of groundwater and coal,which is much worse in the southern region.
We present a method using multiple satellite clocks through the weight to determine the time base in autonomous orbit determination.On the basis of forecasting the clock errors of 32 GPS satellites in using the quadratic polynomials,Chebyshev polynomials,and the gray model,the good quality satellite clocks and forecast models are selected to establish the time base through certain weight.The experimental results show that using several satellite clocks to determine the time base will improve forecast accuracy and the results will be more stable,and the maximum residual is 42 ns when forecasting 180 days.
Based on the basic principles of elementary algebra,a fast and stably recursive algorithm for computing second derivative of associated Legendre's functions is derived.Numerical tests suggest that this new approach is exactly as precise as general ones.But the principal strength of the new approach is that it is much faster than general ones in computation speed(at least twice as fast).The method is non-singular(the relative accuracy can be achieved to 5×10-10 up to degree and order 3 600 at the poles) and simplicity of formulation and implementation(just need a few lines of code).The approach can compute the second derivative of associated Legendre functions of any latitude quickly and accurately,which is very important for gravity gradient data processing of GOCE satellite.
We have done some analysis about the effects of two separate oscillators in RF and in baseband on carrier-phase measuring.And we propose a model for the error of carrier-tracking loop,which is based on all kinds of oscillator's error sources.The analysis and experimental results show that two different clock sources could result in carrier phase measurement error,and the carrier-tracking loop measurement error caused by oscillator could be reduced by increasing the loop noise bandwidth.Moreover,that measurement accuracy can also be advanced by reducing h-factor and g-sensitivity.Additionally,the measurement quality of carrier phase could be improved by adopting a single highly stable and low g-sensitivity oscillator in choosing the GNSS receiver clock.
The method to identify the tropopause height directly from the bending angle profile of global positioning system(GPS) radio occultation(RO) is studied.Using the GPS RO observations provided by the Constellation Observing System for Meteorology,Ionosphere and Climate(COSMIC) mission,the heights of the tropopause are identified directly from the RO bending angle profiles.These tropopause heights are compared with the cold point tropopause(CPT) and the lapse rate tropopause(LRT) determined from the temperature profiles of the corresponding RO events,as well as the CPT and the LRT derived from the radiosonde observations occur within 300 km and 3 hours of the RO events.The results show that to identify the tropopause directly from the bending angle profiles of GPS RO observations is feasible.
Multi-satellite altimetry has provided a wealth of data for measuring the long-term sea level change,T/P,Jason-1 and Jason-2 construct a seamless record of global sea level change from 1993 to present.We present the results of our calibration activities,including data comparisons during the tandem period of the missions,during which we resolve the relative bias between the missions,as well as comparisons to independent tide gauge data.When the entire record is assembled,global mean sea level change from 1993-2011 is 3.12±0.4 mm·a-1,and interannual variation is strongly correlated to El Nio phenomenon.
Based on ionospheric and tropospheric delay calculated through a GPS reference station network,ordinary Kriging interpolation with Exponential and Gaussian functional model was investigated to estimate epoch-by-epoch ionospheric and tropospheric delay respectively for network-RTK user station.A GPS reference network including six stations(baselines range from 38.8 km to 132.7 km) was used to test Kriging interpolation method.Experimental results show that approximate 2 cm and 5 cm interpolation accuracy respectively for ionospheric and tropospheric delay for a baseline of 79.1 km is achieved using ordinary Kriging interpolation,which indicates that ordinary Kriging(Exponential and Gaussian functional model) is suitable for atmospheric delay interpolation of user station in medium-and long-range network-RTK system.
The precondition of integrity calculating equation is usually based on the Gaussian distribution for pseudo range errors.When the assumed Gaussian distribution of range error is contaminated,the calculation results will not protect user position error anymore which will result in additional integrity risk.The integrity equation based on Non-Gaussian distribution was proposed and analyzed.The definition of probability overbounding and two models of multipath errors were introduced.A Gaussian distribution was adopted to overbound the probability of the Non-Gaussian distribution,and the new inflation variance scale was calculated to substitute the variance scale based on Gaussian distribution.The integrity equation was calculated using the new variance scale to gain a safer vertical protect level and horizontal protect level avoiding the additional probability of hazard mislead information and make the integrity equation to be more rigorous in theory.Through the simulation and analysis it is shown that both of the improved integrity equations could Gaussian probability overbound the error which is contaminated,and the first improved equation is more conservative than the second one,and the second improved equation is more optimal and lead to a better availability and continuity.
After the establishment of 2000 Chinese Geodetic Coordinate System(CGCS2000),it is one of major jobs to unify various coordinate systems to the CGCS2000.Because the similarity transformation methods applied in the practice for coordinate transformation are in general not so accurate to unify different coordinate systems,an alternative collocation is presented for coordinate unification.It is needed that the prior covariance matrices between the signals and the observations should be consistent with their uncertainties.Otherwise,the coordinate of the stations provided by the collocation transformation will be unreasonable.An adaptive collocation estimator is applied by which the contributions of the signals and the observations to coordinate transformation are balanced.The corresponding adaptive factor is constructed by the ratio of the variance components of the signals and the observations.An estimator of the variance components for the collocation is used.Reasonable and consistent covariance matrices of the signals and the observations are achieved through the adjustment of the adaptive factor.The actual calculation from Xi'an Geodetic Coordinate System 1980(XAS80) to CGCS2000 shows that the accuracy of coordinate transformation is improved by using the adaptive collocation model.
An automatic image match method based on SIFT features with match-support measure is presented for multi-source remotely sensed images.In order to adjust SIFT match algorithm for multi-source remote sensing images,the match-support measure is introduced for similarity measure.First,a SIFT feature descriptor is built and the points satisfying the minimum Euclidean distance of the candidate matched points between reference image and match image are selecud.Second,we calculate the match-support measure among these candidate matched points respectively.Finally,we employ the relaxation method to discard the false matched point pairs.A stereo of SPOT-5 HRG imagery and aerial image are selected and used for experiment.The empirical results are compared with the results of traditional grey correlation method and conventional SIFT feature match method.The results show that the SIFT feature match method with match-support measure is reliable and efficient for automatic multi-source remotely sensed image match.
An improved feature matching method based on Harris-Laplace and SIFT descriptor is proposed.Because of the instability of low altitude remote sensing platform,the difference of spin deflection angle and scale between low altitude remote sensing imageries is great.The results obtained by matching method based on area grayscale can't meet the real requirements.The feature points detected by SIFT algorithm are easily affected by image noise and slight texture change.With the proposed method,Harris-Laplace is used to detect key points of the image,which are invariant to illumination change,image noise and scale change.And then the orientation of these key points is determined to form feature points from these key points.These feature points are described by SIFT descriptor,and matched using BBF algorithm and RANSAC algorithm.One experiment is introduced,which uses low altitude remote sensing image with high resolution as input data.The experimental results show that the proposed method possesses higher matching accuracy at the same matching speed compared with the matching method based on SIFT algorithm.
Multispectral image is interpolated in each band using Poisson equation with panchromatic image as guidance based on the known condition.The resulting multispectral image keeps most spectral information of original one and possess clear details as the same as panchromatic image.The method works without limitation of band quantity and association with Multigrid solver improves efficiency of data processing.The values of quality index on RASE,ERGAS,spatial detail and SSIM of the proposed new method do well or better compared to traditional image fusion ones in experiment on QuickBird and IKONOS images.
Persistent scatterer InSAR was used to detect surface subsidence in the area around the Yangbajing geothermal power plant due to extraction of ground water with twenty high resolution TerraSAR-X spotlight SAR images collected between March and November 2010.The results suggest that land subsidence in the areas of geothermal wells is up to 25 mm·a-1 whilst the subsidence in the basin is less than 1 mm·a-1.And the correlation between TerraSAR-X and ASAR derived mean velocities is 0.76.TerraSAR-X high resolution spotlight SAR images can provide higher density of PS points than ASAR data,and also can reveal the detail change and micro-displacement in a single ground object.
In 2D SAR imaging,the ambiguity problem is hindering the SAR image interpretation.A new method of compressive sensing(CS) is used to solve the spectral analysis problem in SAR tomography for the first time.The signal reconstruction is demonstrated using simulations and TerraSAR-X spotlight data of Berlin.TomoSAR with CS has huge potential,because not only multiple scatterers inside one resolution cell can be separated,the elevation positions and height of scatters can be accurately measured in the reflectivity slice,but also CS is more robust to noise,has lower computational effort and use less data.
In order to expand the applicable scope of electromagnetic model,a new approach was proposed after recombining unknown parameters about building and ground in this model.The new calculation process was consisted of two steps: initial building height firstly estimated by layover measurement of building roof,and then building height refined by electromagnetic model which was resolved in the system of simulated annealing.To validate this method,heights of three buildings were retrieved from a Radarsat-2 image with 3-meters resolution.The results show that the relative error of building height retrieval is less than 10% in the experiment data.
We present an improved destriping method using self-adaptive moment match after analyzing the characteristics of random strip noises appearing in panchromatic imagery.Firstly,we classify the imagery into different parts according to gray scale.Then we dealt with each part using standard moment match method.The new method will lead to less gray scale distortion than standard moment match method.Finally,high resolution panchromatic imagery acquired from ZY1-02C is adopted to test the effectiveness of our proposal algorithm.The results show that the imagery have advantages at both denosing and fidelity.
A fast algorithm for imaging time window prediction of optical satellites considering the J2 Perturbation was represented.An imaging condition equation about eccentric anomaly is drawn based on a simplified feature cone model.In order to solve the transcendental equation by Newton iteration,a hybrid method for initial value selection was presented in detail.A latitude circle was exploited to potential initial acquisition,and the characteristic of periodic drift of sub-satellite point was utilized for the initial value filtering.The experimental results show feasibility of the proposed method.
Aiming at the huge data amount and pixel complex ownership of remote sensing images,a prototypes-extraction spectral clustering algorithm for remote sensing image segmentation was proposed.Firstly,the generalized fuzzy c-means algorithm was adopted to perform an over-segmentation of the image,and the obtained clustering prototypes were regarded as the representative points of segmentation regions to reduce the data amount of original image.Secondly,the similarity matrix between the representative points was constructed,and then the spectral graph partitioning method was utilized to cluster the representative points.Eventually,based on the clustering result of representative points,the image pixels were reclassified to obtain the final image segmentation results.There are three parameters in the prototypes-extraction spectral clustering algorithm.In order to overcome the parameter sensitivity and inherent randomness of this method,an ensemble strategy was further introduced into the method and its ensemble algorithm is presented.The segmentation experiments on artificial texture and remote sensing images show that this proposed ensemble method behaves well in segmentation performance.
A method for multi-objective tasks scheduling based on information gain was proposed.In order to describing the understanding of target state for combat system,information gain of every target was calculated.The information entropy was used to describe the uncertainty of target information.On the basis of which,the information gain in the detection recognition,and tracek state was carefully analyzed.The capability that the extended kalman filter could estimate the state of target was used to analyze the underwater bearings-only passive target motion.The results of simulation show that the information entropy could quantificationally describe the combat tasks scheduling,and the method is feasible and practical.
A set of system of multi-channel spectral reconstruction was proposed using basis functions.In order to improve the spectral reconstruction accuracy,the digital response of the system has been processed by linear correction functions.In the experimental results the minimum RMSE of the reconstruction spectrum can reach 0.006 87,the minimumcolor difference can reach 0.02,the average color difference is only 2.25.
Based on the spatial position and the geometric characteristics of geographical objects,we present a method to uniquely identify geographical objects by combining their rank Quadtree grid index with spatial morphology.Based on the classic rank Quadtree grid method,we devise an algorithm to extract representative points,outline,and orientation of geographical objects in each grid.We integrate the geometry and grid information to achieve the unique identification of spatial objects.The method is applied to Nanjing city in China to identify the unique spatial location of spatial objects,and it shows improvement in the speed of spatial positioning,searching and querying of spatial objects.
Spatial indices are used by spatial databases to optimize spatial queries.We introduce a parallel spatial range query algorithm based on VoMR-tree index.The MR-tree is firstly augmented to store the nearest neighbors and constructs the Voronoi diagram.Then a range query algorithm based on VoMR-tree index is proposed.In processing a range query,the data partition method so that can improve the efficiency by parallelization in distributed database is discussed.The experimental results show that the proposed method improves the performance of range query processing in comparison with the widely-used methods.
MA-ESPO method was put forward.Both in theory and in experiments,MA-ESPO can completely resolve 2D ESPO in raster method.Further more,obstacles,source shapes and destination shapes in MA-ESPO can be shapes in all form.It's the generalized solution of the method Dijkstra.MA-DTO(map algebra-distance transformation with obstacles) that actually generates all distance toward fountain of all points in the whole obstacle space was given at last.This method prepares the key work of finding shortest path for all points in the space,thereby comes to be the key technique for Voronoi generation of arbitrarily shaped figures in E2 obstacle space.
Disaster-formative environment can magnify or shrink the vulnerability of hazard-affected body and the losses of disaster.Based on geography and cartography science,from the perspective of disaster system,the problem of linear hazard-affected body′s cartographic generalization was discussed based on layer constraints and Douglas-Peucker.Taking railways as an example,the constrained layers database was constructed,the six layers were seismic long-term intensity zoning,the risk of landslides disasters,and activity level of debris flow,mean annual maximum snow depth,flooding frequency,maximum annual day numbers of dust storms and the distribution of lakes.Combined with railway density and risk matrix of integrated hazard intensity,the automatic generalization of railway hazard-affected bodies was done in different regions and sections.The results reveal a regional rule for railway density distribution under multi-scales.
Spurious increments exists inevitably in the results of difference operator because of data inconsistency in the process of increments recognition,and it has reduced the accuracy of change.The existing methods using quantitative threshold,lead to true increments over-removed and spurious increments not recognized,and reduce the accuracy of the results.With the heavy demands in updating of National Spatial Database at scale of 1∶ 50 000,a new method called topological quantitatively method is proposed,which integrates topological relations and buffer analysis to remove the spurious increments of area water.The experimental results show that the proposed method is valid and has stronger practicality.