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Table of Content

    25 December 2012, Volume 41 Issue 6
    Research and Establishment of China’s Digital Land Boundary
    2012, 41(6):  791-796. 
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    China has the world’s longest land boundary line with the length of over 22,000 kilometers and borders 14 countries. The state boundary and border regions are characterized by extreme diversity in terms of geology, topology as well as culture, which makes the boundary delimitation, demarcation and maintenance very complicated and challenging. This paper gives a brief introduction of the research and development on the state digital boundary. A comprehensive spatial boundary database had been set up by spatial integration of multi-media, multi-temporal and multi scale boundary documents and data. Special information processing and analysis systems for delimitation and demarcation had been successfully developed by combing boundary legal knowledge and digital terrain analysis. Information systems for regular and daily boundary maintenance were also developed and now in operational use.

    Optimal Carrier-phase Combinations for Triple-frequency GNSS Derived From an Analytical Method
    2012, 41(6):  797-803. 
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    Triple-frequency carrier-phase combinations can improve the success rate of ambiguity resolution and the reliability of cycle-slips detection and repair. In this paper, noise amplification factor of combinations is expressed as the function of two parameters which are related to the wavelength and ionospheric scale factor of combinations respectively, and then an analytical method for solving optimal linear coefficients with minimal noise amplification factor is presented, when the wavelength and ionospheric scale factor of combinations are given. It is shown that the ionospheric amplification factor of combinations with long wavelength and low noise increased when the sum of the linear coefficients increased, and the ionospheric amplification factor is about 2.3 times of the sum. Furthermore, the wavelength of combinations with small ionospheric amplification factor and low noise decreased when the sum of linear coefficients increased.

    The Tikhonov_Least Squares Collocation Method for Determining Geoid
    2012, 41(6):  804-810. 
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    LSC method (least squares collocation method) attracted widespread attention due to the integration of different types of gravity observation data to determine the geoid. But the observation errors are amplified by the small singular values of the ill-posed covariance matrix, leading to the unstable and low-accuracy collocation results. This paper proposed the Tikhonov-LSC method, namely in the LSC method to introduce the Tikhonov regularization algorithm, based on the GCV method to select the regularization parameter of the covariance matrix, and using the parameter to modify the small singular values of the ill-posed covariance matrix, in order to inhibit its observational error amplification impact. Using the Tikhonov_LSC method to determining the Geoid can effectively improve the stability and accuracy. The experiments using gravity anomalies based on the EGM2008 in three different regions such as mountainous region, hill and ocean region to determine the geoid verify the validity of the method.

    Study on the Determination of Crossovers by Piecewise Fitting of Satellite Ground Track
    2012, 41(6):  811-815. 
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    Navigation Satellites Velocity and Acceleration Computation: Methods and Accuracy Analysis
    2012, 41(6):  816-824. 
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    The velocities and accelerations computation of the navigation satellites is the prerequisite of the velocities and accelerations determination of the receivers. This paper made a systemic analysis of the different methods to calculate the velocities and accelerations of the navigation satellites, including (1) the closed analytical method based on broadcast ephemeris; (2) the numerical differencing method based on position series of the satellite; (3) the analytical differencing method based on position series of the satellite. Firstly, the analytical expressions were deduced based on broadcast ephemeris, three types of broadcast ephemeris, including Kepler elements, GEO, and position-velocity type are discussed. The results can be drawn from precision comparison as follows: (1) The accuracy of velocity and acceleration derived from broadcast ephemeris is relative low, and can not match the high precision applications, such as airborne gravimetric measurement; (2) The acceleration accuracy is higher derived from position-velocity broadcast ephemeris while the Kepler type has higher velocity accuracy; (3) the orbit height is one of the factors of the computation precision. Then, the analytical differencing and numerical differencing based on precision ephemeris to derive velocities and acceleration were analyzed and compared, the results shows that although the analytical method has advantages on efficient, the velocities computation precision is lower for the orbit analytical model built from short term position series is inaccurate, however, the acceleration computation precision compared to the numerical differencing method. In high precision applications, numerical differencing methods should be used for its highest velocity and acceleration computation accuracy. Finally, a static experiment is conducted which data from two CORS (Continues Operational Reference System) stations to evaluate and compare the computation accuracy among the methods mentioned above.

    An Algorithm of Combined GPS/GLONASS Static Relative Positioning
    2012, 41(6):  825-830. 
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    The model of combined GPS/GLONASS static relative positioning is introduced. The ambiguities of double difference GLONASS observations are expressed as the single difference ambiguity of reference satellite and double difference ambiguities. It is proved via error analysis that the single difference ambiguity of GLONASS can be solved as a real number, while the double difference ambiguities must be solved as integer parameters. And the weights of GPS and GLONASS observations are determined by using Helmert variance component estimation. The numerical examples with real GPS/GLONASS observations indicate that the accuracy of combined GPS/GLONASS positioning is better than that of a single system positioning. Especially, compared with the single GLONASS system, the accuracy is greatly improved, and compared with single the GPS system, the improvement is about 10% in the case of single epoch baseline solution. When available satellites of a single system are less than four, combined GPS/GLONASS positioning has more advantages.

    The Method and Application of Hole Boundary Extraction for Multi-valued Surface Repair
    2012, 41(6):  831-837. 
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    Abstract: For traditional extraction methods of hole boundary were affected by noise and single-valued surface, this paper proposed an automatic extraction method for the multi-valued surface repair to overcome the problem of overlapping projection. First, the k-nearest neighbors calculated from the scattered point clouds were projected to the plane by the method of ALS; then the mesh was divided within the plane to extract the boundary grid and propose boundary line using the minimum convex hull; finally, the hole boundary and the object boundary was identified. In order to verify validity, the method is applied to fill up the hole and surface reconstruction which is used to analyze and evaluate the accuracy using the quantitative evaluation index of the maximum distance and the average distance from the sample points to the built surface model. The results show that ALS and the minimum convex hull can keep characteristics and avoid the problem of overlapping projection. The extracted hole boundaries are very precise to meet the needs of follow-up modeling.

    Research on SAR Image Speckle Reduction Using EMD and Principle Component Analysis
    2012, 41(6):  838-843. 
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    By combining the empirical mode decomposition(EMD) and principle component analysis(PCA), a new speckle reduction method based EMD is proposed for logarithmic SAR images. Based on the Statistical properties of logarithmically transformed speckle and energy distribution model of decomposed Gaussian white noise by EMD, the noise energy in each intrinsic mode function is approximately calculated. After the intrinsic mode function is decomposed by PCA, to further remove the noise and keep useful details, we select the appropriate principal components according to the noise energy proportion in intrinsic mode function and the decomposition characteristics of PCA, then reconstruct the intrinsic mode function by the selected principal components. The experimental results show that the SAR image edges are retained better and the speckles are removed effectively with the proposed method.

    A New Approach of Weighted Stacking Based on Common Master Image and Its Application in Ground Subsidence Monitoring
    2012, 41(6):  844-850. 
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    A new weighted stacking approach considering the quality weight of coherence image was put forward, whose weight is set according to the quanlity of coherent points in the coherent images, this method can avoid low-coherence images’ participation in weighted calculation. The basic principle and data processing flow of weighted stacking based on common master image were introduced first. Then Its mathematical model of optimum selection of the common master image, weakening influence of atmospheric delay and increasing SNR(Signal to Noise Ratio)was improved. which reduces the requirements of image quantity, and higher surveying precision. Based on ENVISAT ASAR data of 11 scenes from Tianjin district during the period of 2003-2006, Image No.14529 was selected as a common master image by model optimization to calculate ground subsidence in weighted Stacking. Its precision is as high as high-precision leveling, higher than the conventional DInSAR and Stacking.

    The Necessary and Sufficient Condition of Camera Calibration and Attitude Determination based on Vanishing Points with Their Uncertainty Analysis
    2012, 41(6):  851-856. 
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    This paper discusses and demonstrates the uncertainty of camera calibration and attitude determination based on three orthogonal vanishing points. The necessary and sufficient condition of parameters determination is given out. Especially, under the condition of joint error distribution of two orthogonal directions vanishing points (VX, VY), how to solve the third vanishing point (VZ) is discussed. Assessment the uncertainties of vanishing points based on relative error ellipse is supplemented. Furthermore, the algorithms of simulating the spatial distribution of the VZ and estimating its area size are presented by Monte-Carlo method. This article is not only enriched the theory and methods of vanishing point, but also reveals the laws and the uncertainty of their spatial distributions, which provides a theoretical basis for studying the universality of vanishing point basic application.

    Remote Sensing Image Change Detection Using Particle Swarm Optimization Algorithm
    2012, 41(6):  857-863. 
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    Aiming at the restriction of training samples distribution and limitation of feature combinations caused by traditional methods in the current multi-temporal remote sensing image direct change detection application, this paper introduces the particle swarm optimization(PSO)method to the field of remote sensing change detection, and propose a new change detection method based on PSO algorithm. In the processing of change detection, it automatically searches the change rules, so it can directly achieve the change information at one time. Selecting Beijing area as experimental area, this paper demonstrates the land cover change detection information extraction in Beijing area from 2000 to 2006, 2006 to 2009 using the new method. The PSO method is also compared with C4.5, PART, Maximum Likelihood methods, the results show that the PSO algorithm can search change rules automatically, and can achieve simpler rule than C4.5 and PART, can achieve high precision than the other three methods.

    Deformation Model of Time Series Interferometric SAR Techniques
    2012, 41(6):  864-869. 
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    Abstract: Time series Interferometric SAR (InSAR) techniques represented by permanent scatterers InSAR and small baseline subset approaches overcome the decorrelation limitations associated with traditional repeat-path differential SAR interferometry, thus have been gradually put into operational uses for ground deformation mapping. It is usually assumed that the deformation process can be modeled as a dominant linear component plus a nonlinear residual component when time series InSAR techniques are used. Whereas, if the real deformation scenario presents strong nonlinearity, this kind of deformation model may bring out erroneous results. This paper focuses on the deformation model of time series InSAR analysis. At first, the process of solving the interferometric phase equations and estimating the linear deformation rate is analyzed for a typical time series InSAR analysis. When the reality of deformation is deviated significantly from a linear model, and at the same time the density of extracted point targets is not good enough, the linear deformation rate can not be estimated accurately. Then, on the basis of the famous Weierstrass approximation theorem, we propose a polynomial deformation model, that is, the whole deformation will be represented by a polynomial plus the residual rather than a straight line plus a nonlinear component. Also the method to solve the interferometric phase equations under the polynomial deformation model is given. The proposed method is tested to map the ground subsidence of Taiyuan, Shanxi province of China. Totally 23 ALOS PALSAR images acquired between 2003 and 2009 are processed with the small baseline approach. In comparison, the small baseline approach with both the linear deformation model and a three-order polynomial deformation model are conducted. Both results of subsidence retrieval are compared with the leveling observation. It is demonstrated that the small baseline approach with the 3-order polynomial model can not only achieve more accurate deformation estimate, but also generate denser point targets. Since a continuous process can always be better approximated by a higher-order polynomial than a lower-order one, the proposed polynomial deformation model has the potential of replacing the wide-used linear deformation model for time series InSAR analysis.

    Automatic Road Extraction In Complex Scenes Based on Information Fusion From LiDAR and Remote Sensing Imagery
    2012, 41(6):  870-876. 
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    Automatic road extraction from remote sensing images in urban area has been a very challenging task due to the complexity of the scene, especially in the occluded or shadowed areas. This paper proposes an integrated method to fuse LiDAR data and high resolution imagery for automatic extraction of road centrelines. Firstly the LiDAR point cloud is filtered to get the ground points whose intensity data is used to detect initial road centrelines and key points of the roads. A road model is then built on the intensity and dispersion of the ground points as well as spectral information obtained from the high resolution image. Based on the model, the dynamic programming algorithm is applied to find the optimal road centrelines linking the key points which are selected by evaluation. The experimental results indicate its effectiveness in automatic road extraction in urban and complex scenes.

    Stereo-camera Calibration with Restrictive Constraints
    2012, 41(6):  877-885. 
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    In the field of computer vision and close range photogrammetry, it is critical to accurately calibrate the intrinsic parameters and the fixed relative orientation relationship between the two cameras of the stereo-camera system used for high precision 3D reconstruction. In this paper, six fixed and independent relative orientation constraints between the two cameras are derived firstly, and then self-calibration bundle adjustment with restrictive constraints is employed to calibrate the stereo-camera system. Finally, synthetic and real data are both employed to verify the performance of the calibration method proposed in this paper. The experiment result reveals that the proposed relative orientation constraints can effectively increase the redundant observations of the calibration adjustment system, and this can improve the accuracy and stability of the calibration. This method can also be extended to other stereo-camera systems which consist of more than two cameras.

    PS-InSAR Deformation Monitoring Data Processing Based on Multi-reference Points
    2012, 41(6):  886-890. 
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    Single-reference point Permanent Scatterers Interferometry (PS-InSAR) can result in an unstable and unreliable solution in the data processing of baseline network adjustment. This paper advances a multi-reference points PS-InSAR data processing method by adding ground monitoring data and the corresponding mathematic model is derived. By introducing multi-reference points in the PS baseline network processing, the solution’s stability and reliability can be improved due to extra observations condition. In the experiment, thirteen Envisat ASAR images covering the Xi’an city and five reference points composing of Corner Reflectors (CR) and GPS are employed to prove the superiority of the proposed method. Processing these data, average surface deformation field from single-reference point and multi-reference points are created respectively. The results of comparing four checking points show that solution from multi-reference points is much more consistent with ground observation result than single-reference point.

    Synthesis Classification of Remote Sensing Image Based on Improved Pixel-Level and Object-Level Methods
    2012, 41(6):  891-897. 
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    The pixel- and object-level classification methods are investigated separately, while the hybrid of them has not been explored. This paper tries new exploration on the hybrid of pixel- and object-level classification, and proposes synthesis classification method for remote sensing image based on improved pixel- and object-level classification. Firstly, an improved RBF neural network classifier is proposed to obtain the pixel-level classification result, and a hierarchy classification model based on improved fuzzy support vector machines and decision tree is utilized to obtain the object-level classification result. Then a specific synthesis algorithm of pixel- and object-level classification is proposed to obtain the synthesis classification result. The experiments show the synthesis classification method can improve the accuracy of classification result effectively and provide more accurate classification result than single pixel- or object-level method.

    A Dynamic Algorithm of Vectorization for Large Claasified Remote Sensing Image
    2012, 41(6):  898-903. 
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    To solve the problem of low efficiency and space bottlenecks of vectorization for large remote sensing image, this paper presents a dynamic algorithm of vectorization for large remote sensing image, based on the policy of verctorizing polygons in the process of vertices extraction. First, the number of vertices in every polygon is counted and it’s used as the factor to judge whether a set of vertices constitute a closed polygon or not; and then during the extraction of vertices, if a set of vertices can constitute a closed polygon, it will be vectorized and its memory will be released. A set of vertices constructs directly into a closed polygon without generating temporary data, created topological structure of vector data during the conversion. Experimental results show that the dynamic algorithm has high efficiency in time and space, and its speed is 3 to 4 times that of ARCGIS (9.2 version).

    Variations of the Earth’s Gravity Field from GRACE, Geophysical Model and Satellite Laser Ranging
    2012, 41(6):  904-909. 
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    Several independent time series of variations J2 in Earth’s gravity field are compared from GRACE, geophysical model and satellite laser ranging (SLR) for the period April 2002 to October 2010. We compute the atmospheric induced J2 variations for both inverted (IB) and non-inverted-barometer (NIB) response of the oceans. The results of the comparison show that the annual term amplitude of J2 in NIB case is bigger by a 3 factor than that in IB case, the difference of the both phase is 47°; At the annual frequency, atmospheric pressure and surface ground water effects are the dominate contributors; For the semi-annual term, the amplitudes and phases of the atmospheric pressure, ocean and surface ground water do not agree very well, especially for the results of the atmospheric pressure in IB case; GRACE, geophysical model and SLR annual J2 estimates agree well. The amplitude from GRACE is bigger about 50 percent. The annual amplitude from SLR is between that from the geophysical model in IB case and in NIB case. The semi-annual amplitude estimated from GRACE and SLR is the same. The difference of the semi-annual variations between geophysical model (IB) and SLR is the biggest.

    A Spatial Shape Simulation Method for Three-dimensional Geological Body Based on Marching Cubes Algorithm
    2012, 41(6):  910-917. 
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    According to the sparse sampling dataset about the geological body in geological investigation, it is difficult to construct the three-dimensional model of geological body. Therefore, we propose a method to implement the three-dimensional implicit simulation for the geological body by marching cubes algorithm. Firstly, the spatial interpolation method is used to predict the distribution of geological body, and then the three-dimensional spatial regular data field of geological body is established. Secondly, the three-dimensional isosurface of geological body is extracted from sparse points by the marching cubes algorithm. Finally, combining with three-dimensional visualization technology of OpenGL, three-dimensional spatial shape of geological body is simulated by tiny triangle approximation in computer graphics. Taken the borehole data in exploration engineering as example, this method has been applied to develop the three-dimensional implicit simulation for ore body. The result of implicit simulation is similar to the delineation of explicit simulation in three-dimensional geological modeling software by human-computer interaction. The method shows the feasible and efficient for the three-dimensional simulation of geological body.

    Seamless Expression of the Global Multi-resolution DEMs Based on Degenerate Quadtree Grids
    2012, 41(6):  918-925. 
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    For realizing simulation and visualization of global multi-resolution terrain efficiently, a seamless modeling method of the global multi-resolution DEM is discussed based on spherical DQG (Degenerate Quadtree Grid) in this paper. The main contents are included as follows: First of all, a new modeling method of global block quadtree based on DQG is developed. Then, an self-adaptable seamless stitching algorithm is designed and achieved, in which the cracks exist within a quadtree block (without limiting the subdivision level of the adjacent nodes), between the different quadtree blocks, or between a quadtree block and a non-quadtree block. Finally, by using VC + + language and OpenGL tools, a relevant experimental visualization system is designed and developed. As a result, the proposed modeling method and the adaptive elimination algorithms of different types of cracks are verified. The experimental results show that the display efficiency of global DEM is improved obviously while ensuring the accuracy of the terrain expression. When the grid was subdivided into 12 levels, the simplification efficiency is 66.8%.

    Noise Error Analysis of Slope Algorithms Based on Grid DEM Derived from Interpolation
    2012, 41(6):  926-932. 
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    The extraction of slope from Grid DEM is generally through difference algorithms using neighbor analysis (NA), its error is subject to 3 factors: DEM error,DEM data structure and slope algorithms. This study will focusing on slope noise error that is caused by DEM noise error component, this paper will deduct the slope error model on the condition of interpolating points to grid DEM, and evaluated how noise error autocorrelation caused by interpolate influence the slope accuracy. In order to find the rules of noise error autocorrelation influences to slope accuracy, we select case experiment that was taken 5 slope difference algorithms and 4 interpolation methods as example, the experimental results show that slope accuracy can be significantly influenced by DEM noise error autocorrelation, and will be slightly changed with the different interpolation methods and slope algorithms.

    Automated Matching Urban Road Networks Using Probabilistic Relaxation
    2012, 41(6):  933-939. 
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    Multiple spatial data matching is a crucial prerequisite for data integration and interoperability, change detection and data updating. Road network matching is of great theoretical and practical significances in Navigation, Intelligent Transportation System and Location-Based Services. The paper proposes a probabilistic relaxation approach for matching urban road networks. The proposed method starts with an initial probabilistic matrix according to the geometric dissimilarities, and then integrates the effects of neighbouring roads to update the old probabilistic matrix until it is convergent to a specified small value. Finally, on the basis of the convergent probabilistic matrix, the structural similarity of each candidate pair is calculated and the corresponding rules are defined to select and refine 1: 1, 1: M and M: N matches. Two experiments of matching between Open Street Map network data and professional road network data in Wuhan and Zurich show that our method achieves a robust matching precision for large non-rigid deviation, is independent of matching direction, and successfully matches 1: 0 (Null), 1: 1 and M: N pairs.