Table of Content

20 January 2016, Volume 45 Issue 1

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Geographical National Condition and Complex System

WANG Jiayao, XIE Mingxia

2016, 45(1):  1-8.  doi:10.11947/j.AGCS.2016.20150350

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The significance of studying the complex system of geographical national conditions lies in rationally expressing the complex relationships of the “resources-environment-ecology-economy-society” system. Aiming to the problems faced by the statistical analysis of geographical national conditions, including the disunity of research contents, the inconsistency of range, the uncertainty of goals, etc.the present paper conducted a range of discussions from the perspectives of concept, theory and method, and designed some solutions based on the complex system theory and coordination degree analysis methods.By analyzing the concepts of geographical national conditions, geographical national conditions survey and geographical national conditions statistical analysis, as well as investigating the relationships between theirs, the statistical contents and the analytical range of geographical national conditions are clarified and defined. This investigation also clarifies the goals of the statistical analysis by analyzing the basic characteristics of the geographical national conditions and the complex system, and the consistency between the analysis of the degree of coordination and statistical analyses. It outlines their goals, proposes a concept for the complex system of geographical national conditions, and it describes the concept. The complex system theory provides new theoretical guidance for the statistical analysis of geographical national conditions. The degree of coordination offers new approaches on how to undertake the analysis based on the measurement method and decision-making analysis scheme upon which the complex system of geographical national conditions is based. It analyzes the overall trend via the degree of coordination of the complex system on a macro level, and it determines the direction of remediation on a micro level based on the degree of coordination among various subsystems and of single systems. These results establish specific improvement strategies and achieve the goals of the statistical analysis of the geographic variables.

Independent Component Analysis of Water Storage Changes Interpretation over Tibetan Plateau and Its Surrounding Areas

WEN Hanjiang, HUANG Zhenwei, WANG Youlei, LIU Huanling, ZHU Guangbin

2016, 45(1):  9-15.  doi:10.11947/j.AGCS.2016.20140447

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We first use the independent component analysis (ICA) method to decompose the water storage changes derived from 132 months (2003-01—2013-12) gravity recovery and climate experiment (GRACE) measurements, and then compare the results with those from NOAH and WGHM hydrological models. The comparison results of components show that the first principal components from the water storage changes and hydrological models agree well, and the correlation coefficients are 0.884 and 0.877 respectively. It shows that GRACE derived water storage changes and hydrological models over Tibetan Plateau and its surrounding areas have a strong consistency. For spatial pattern, the amplitudes of GRACE-derived water storage changes are larger than that of hydrological models, which may be caused by the groundwater changes included in the GRACE-derived water storage changes.

Research and Realization of Deformation Monitoring Algorithm with Millimeter Level Precision Based on BeiDou Navigation Satellite System

XIAO Yugang, JIANG Weiping, CHEN Hua, YUAN Peng, XI Ruijie

2016, 45(1):  16-21.  doi:10.11947/j.AGCS.2016.20140649

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The deformation monitoring algorithm with millimeter level precision based on BeiDou Navigation Satellite System (BDS) was researched. The TurboEdit method was improved to detect small cycle slips, e.g. 1 cycle. Focusing on BDS constellation, a more efficient algorithm used to construct double-differenced observations was developed. The Bootstrap+Decision function method was utilized to improve the probability of biases fixing. Based on the improved algorithm above, a deformation monitoring software based on BDS was achieved. Afterwards, the availability of BDS in the field of deformation monitoring was analyzed in terms of satellites distribution and precision and accuracy of solutions, utilizing the observations acquired from the experimental platform. The conclusion was drawn that currently BDS is similar to GPS in terms of satellites distribution in the test area. The precision of short baselines derived from BDS is better than 1 mm for the horizontal components, better than 2 mm for the vertical components, which is still a little lower than GPS.

An Algorithm for Partial EIV Model

WANG Leyang, YU Hang, CHEN Xiaoyong

2016, 45(1):  22-29.  doi:10.11947/j.AGCS.2016.20140560

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A new thinking for solving partial errors-in-variables (partial EIV) model was proposed. Through the transposition processing in partial EIV model, a new functional model was reconstructed. Adjustment of indirect observations has been used two times to calculate the model parameters and the stochastic elements in coefficient matrix, translating total least squares problem to least squares problem. It also achieves high convergence rate through some simple variables transformation. Finally, real and simulation data were implemented to compare with the existing algorithms and to analysis the applicability of the proposed algorithms. The results show that the new algorithms are feasible and it can achieve the same values with the existing algorithms.

Variance Component Estimation in the Seamless Affine Transformation Model

LI Bofeng

2016, 45(1):  30-35.  doi:10.11947/j.AGCS.2016.20140676

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With the seamless affine transformation as an instance, the variance component estimation (VCE) theory is studied in the seamless datum transformation. The VCE formula of the seamless transformation model is derived. The results from the simulation experiments show that the VCE can correctly recover the objective variance components of coordinates in two datums. As a result, the accuracy of seamless transformation can be improved.

An Improved Coherent Targets Technology for Monitoring Surface Deformation

WANG Mingzhou, LI Tao, JIANG Liming, XU Kan, WU Wenhao

2016, 45(1):  36-43.  doi:10.11947/j.AGCS.2016.20140617

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How to obtain a more comprehensive collection of coherent points from interferometric datasets and analyze deformation time-series is the difficult and hot spot in current research. An improved coherent targets technology is proposed, which can obtain a more comprehensive and reliable collection of coherent points and improve temporal-spatial resolution and precision of deformation signal. Based on similar backscattering properties of the same ground object, non-parametric hypothesis test is used to extract the homogeneous pixels and nonlocal filter is applied to improve the quality of interferogram. Meanwhile, the systematic phase is removed based on multi-resolution maximum likelihood estimation (MLE) of fringes algorithm, then the coherence of homogeneous pixels is estimated stationarily. Thereby more coherent points can be obtained. 20 TerraSAR-X stripmap images are exploited by the conventional CT and the proposed method to investigate the ground deformation of the reclaimed lands in Hong Kong. Experimental results show that this method can effectively improve the density of coherent points in the reclaimed lands with sparse vegetation and obtain a more reliable result.

Improved Algorithm for Weak GPS Signal Acquisition Based on Delay-accumulation Method

LI Yuanming, LI Jing, ZHANG Peng, ZHENG Yong

2016, 45(1):  44-49.  doi:10.11947/j.AGCS.2016.20140224

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A new improved algorithm is proposed to solve the problem of GPS weak signal capture that the traditional algorithms are unavailable to capture under a weak signal environment. This algorithm is based on the analysis of double block zero padding (DBZP) algorithm and it adopts the delay-accumulation method to retain the operation results temporarily which are discarded in DBZP algorithm. Waiting for delaying 1 ms, the corresponding correlation calculation results are obtained. Then superimpose the obtained results with the operation results retained temporarily and compare the coherent accumulation results with the threshold value. The data measurements are increased by improving the utilization rate of correlation operation results in the improved algorithm on the premise of increasing little computation. Simulation results showed that the improved algorithm can improve the acquisition algorithm processing gain and it is able to capture the signals whose carrier-to-noise ratio(C/N0) is 17 dB-Hz and the detection probability can achieve to 91%.

The Algorithm of Single-epoch Integer Ambiguity Resolution between Middle-range BDS Network RTK Reference Stations

ZHU Huizhong, XU Aigong, GAO Meng, YANG Qiushi

2016, 45(1):  50-57.  doi:10.11947/j.AGCS.2016.20140525

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The algorithm of double frequency carrier phase integer ambiguity resolution between middle-range reference stations at single-epoch is proposed. The ambiguity candidates of B1 frequency and B2 frequency carrier phase are selected by linear relationship between carrier phase ambiguities of B1 frequency and B2 frequency carrier phase. The double difference ionosphere delay errors can be calculated by the ambiguity candidates of double frequency carrier phase. Then the linear calculation model of double difference ionosphere delay errors can be established by the double difference ionosphere delay errors according to the spatial relationship between the ionosphere delay errors of each satellites on reference stations. And the ambiguities of B1 frequency and B2 frequency carrier phase are searched and fixed in the establishing of the linear calculation model of double difference ionosphere delay errors. This algorithm is tested by the data of BDS CORS network. The results indicate that the double difference integer ambiguity between reference stations can be fixed at single-epoch, and this algorithm avoids the effect of cycle clips.

LiDAR Point Cloud Registration Based on Plücker Line

SHENG Qinghong, CHEN Shuwen, LIU Jianfeng, WANG Huinan

2016, 45(1):  58-64.  doi:10.11947/j.AGCS.2016.20140415

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The high precision LiDAR point cloud registration is the key to achieve overall point cloud data, in the meantime, to ensure the 3D topological reconstruction of spatial objects. In this paper, a new registration method based on Plücker line is proposed. The conjugate lines between reference point cloud and point cloud to be registered are expressed by Plücker line. Then the collinearity equation based on Plücker line is established by the geometric topology relation of the conjugate lines. Finally the relative position and attitude parameters between reference point cloud and point cloud to be registered are solved by least squares method. Experimental results show that the method has strong geometric constraint and high registration precision.

An Island and Coastal Image Segmentation Method Based on Quadtree and GAC Model

GUO Haitao, SUN Lei, SHEN Jiashuang, CHEN Xiaowei, ZHANG Hongwei

2016, 45(1):  65-72.  doi:10.11947/j.AGCS.2016.20150240

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Island and coastal image segmentation is of great importance for the subsequent coastline extraction, terrain inversion for intertidal zone, analysis of the situation for shore evolution, and so on. Firstly, the advantages and disadvantages of quadtree, geodesic active contour (GAC) model and Canny edge detector used in the island and coastal image segmentation are analyzed. Secondly, an island and coastal image segmentation method is proposed by integrating quadtree, GAC model and Canny edge detector. The advantages of these three kinds of method are taken in the method proposed in this paper. The method introduces the results of Canny edge detector into edge indicator function of geodesic active contour model based on quadtree segmentation, evolutes the level set equation, and realizes island and coastal image segmentation.The experimental results show that the method proposed in this paper is of high speed, precision, reliability and automation for island and coastal image segmentation, even in the weak edges and serious concave edges.

Joint Probability Space Based Self-adaptive Remote Sensing Change Detection Method

WU Wei, SHEN Zhanfeng, WU Tianjun, WANG Weihong

2016, 45(1):  73-79.  doi:10.11947/j.AGCS.2016.20140484

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A variety of factors has led to radiometric variations of the land cover, which severely limits the threshold based change detection method performance. To overcome this problem, we propose a joint probability density space based self adaptive multi-threshold change detection approach. Firstly, the two images of the same geographic area acquired at different time are transformed into the joint probability space. In which, the land cover change pixels are defined as outliers and identified by an iterative method. Then, the extracted outliers are mapped back to the original image space and determine the change area. To illustrate the performance of the proposed method, an experimental analysis on two classical applications is reported and discussed, results show that the proposed method over performed the state of art method in true rate, false alarm rate and omit alarm rate, with high stability.

Nonlinear Spectral Unmixing for Optimizing Per-pixel Endmember Sets

LI Hui, ZHANG Jinqu, CAO Yang, WANG Xingfang

2016, 45(1):  80-86.  doi:10.11947/j.AGCS.2016.20140520

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For a given pixel, fractional abundances predicted by spectral mixture analysis (SMA) are most accurate when only the endmembers that comprise it are used. This paper presents a support vector machines (SVM) method to achieve land use/land cover fractions of remote sensing image using two steps: ①defining the optimal per-pixel endmember set, which removes endmembers based on negative fractional abundances generated by SVM method; ②using SVM extended with pairwise coupling (PWC) to output probabilities as the abundance of landscape fractions. The performances of the proposed method were evaluated with the multiple endmember spectral mixture analysis (MESMA) method, which has been widely applied to map land cover for the goodness of the model fitting. The results obtained in this study were validated by real fractions generated from SPOT high resolution geometric (HRG) image. The best classification results were obtained by the proposed method indicated by the lower total mean absolute error, the higher overall accuracy, and the higher kappa. From this study, the proposed method is proved to be effective in obtaining abundance fractions that are physically realistic (sum close to one and nonnegative), and providing valuable application in selecting endmembers that occur within a pixel.

Line Matching Algorithm for Aerial Image Based on Corresponding Points and Z-plane Constraints

WANG Jingxue, SONG Weidong, WANG Weixi

2016, 45(1):  87-95.  doi:10.11947/j.AGCS.2016.20140527

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Aiming at the problem of line matching and the effectiveness of matching constraints, this paper presents one new line matching algorithm based on corresponding points and Z-plane constraints. Based on the edge points matching results and the line extraction results, the algorithm firstly determines the candidate lines by corresponding points in neighborhoods of lines, also the elevation values of line projection planes, and then obtains the corresponding lines with the similarity constraint between object space and image space. Secondly, it integrates the matching results of “one-to-many” relationship according to the line indexes and merges those into one line, and then translates the matching results into “one-to-one” relationship. Finally, it determines the corresponding endpoints of corresponding lines by using “image-object-image” mapping mode. In the experiments, this paper adopts digital aerial images with classic texture features for line matching, and the experiment results demonstrate that the proposed algorithm in this paper can obtain reliable line matching results.

Fast Registration Method for Point Clouds Using the Image Information

WANG Ruiyan, JIANG Guang, GAO Quanxue

2016, 45(1):  96-102.  doi:10.11947/j.AGCS.2016.20140627

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On the existing laser scanners, there usually is a coaxial camera, which could capture images in the scanning site. For the laser scanners with a coaxial camera, we propose a fast registration method using the image information. Unlike the traditional registration methods that computing the rotation and translation simultaneously, our method calculates them individually. The rotation transformation between the point clouds is obtained by the knowledge of the vision geometry and the image information, while their translation is acquired by our improved ICP algorithm. In the improved ICP algorithm, only the translation vector is updated iteratively, whose input is the point clouds that removing the rotation transformation. Experimental results show that the rotation matrix obtained by the images has a high accuracy. In addition, compared with the traditional ICP algorithm, our algorithm converges faster and is easier to fall into the global optimum.

Matching Method for Road Networks Considering the Similarity of the Neighborhood Habitation Cluster

WANG Xiao, QIAN Haizhong, HE Haiwei, CHEN Jingnan, HU Huiming

2016, 45(1):  103-111.  doi:10.11947/j.AGCS.2016.20140588

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The existing matching methods for the multi-source road data of the same scale mainly consider the characteristics of the road itself, while the effect of the neighborhood features on matching process is generally ignored, which may restrict the further improvement of the matching results. This restriction can be more obvious for the matching data in which the location or rotation differences still exist after the system error rectification. A road network matching method that takes the similarity of the roads' neighborhood habitation cluster into consideration is proposed, which draws on the experience of the human spatial cognitive characteristics for the unfamiliar environment. Firstly, the neighborhood habitation cluster of the road is extracted by the urban skeleton line network; Then by calculating the spatial relation similarity and geometry characteristic similarity of the neighborhood habitation cluster, the matching results can be obtained. The advantage of this method is that for the road data which have obvious location or rotation differences, the similarity of their neighborhood habitation clusters can be treated as a proper matching index. Actually, roads' neighborhood habitation cluster can be a constraint of the road matching process and enhance its robustness. The tests and comparison analysis indicate that this method can solve the matching problems of the road data which still have obvious location or rotation differences after system error rectification and improve the matching correctness.

An Improved QTM Subdivision Model with Approximate Equal-area

ZHAO Xuesheng, YUAN Zhengyi, ZHAO Longfei, ZHU Sikun

2016, 45(1):  112-118.  doi:10.11947/j.AGCS.2016.20140598

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To overcome the defect of large area deformation in the traditional QTM subdivision model, an improved subdivision model is proposed which based on the “parallel method” and the thought of the equal area subdivision with changed-longitude-latitude. By adjusting the position of the parallel, this model ensures that the grid area between two adjacent parallels combined with no variation, so as to control area variation and variation accumulation of the QTM grid. The experimental results show that this improved model not only remains some advantages of the traditional QTM model(such as the simple calculation and the clear corresponding relationship with longitude/latitude grid, etc), but also has the following advantages: ①this improved model has a better convergence than the traditional one. The ratio of area_max/min finally converges to 1.38, far less than 1.73 of the “parallel method”; ②the grid units in middle and low latitude regions have small area variations and successive distributions; meanwhile, with the increase of subdivision level, the grid units with large variations gradually concentrate to the poles; ③the area variation of grid unit will not cumulate with the increasing of subdivision level.

Parallel Algorithm of Spatial Relationship Query between Polygons Based on Heterogeneous Multi-core Architecture

XIE Chuanjie, LONG Zhou, MA Yihang, YOU Zhijie

2016, 45(1):  119-126.  doi:10.11947/j.AGCS.2016.20140463

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The commonly used Plane Sweep algorithm in the spatial relationship query is a serial algorithm, when dealing with huge amounts of spatial data, the efficiency is very low,and the existing parallel computing method is not applicable to normal computer. Aiming at this problem, this paper proposes a parallel algorithm of spatial relationship query between polygons based on heterogeneous multi-core architecture. The algorithm uses STR-tree index to filter out non-intersection polygons first, then decomposes the filtered polygons data into points set and edges set, and constructs a quadtree index for them; under the premise of data accuracy meets the requirement of floating point calculation, uses GPU's powerful batch computing power quickly processing the intersection between edges and calculates the topology relationship between rings, then uses the topology relationship between rings to calculate the DE-9IM model between polygons; compares the DE-9IM model with spatial relationship query condition and outputs the query results. At last, the efficiency and accuracy of the algorithm is verified by experiment.