Table of Content

20 September 2018, Volume 47 Issue 9

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Zone Correction:A SBAS Differential Correction Model for BDS Decimeter-level Positioning

CHEN Junping, ZHANG Yize, ZHOU Jianhua, YANG Sainan, HU Yifan, CHEN Qian

2018, 47(9):  1161-1170.  doi:10.11947/j.AGCS.2018.20170156

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To support the requirement of decimeter-level BDS SBAS service,a type of differential correction,the "zone correction",it is developed. It represents the remaining un-modeled errors of pseudo-range and carrier phase observations,and could be encoded into the current broadcast messages.The zone correction is derived using observations of reference stations,where their coordinates are precisely known. Users receiving the broadcast zone corrections covering its region,use them to correct the observations,thus the observation modeling errors are reduced and positioning accuracy can be improved.It is analyzed that the impact of parameter updating rates and the distance between users and the zone center on the user positioning accuracy. Data of the BDS tracking network in the China continent is used to validate the proposed model.Results show that mean positioning accuracy reaches 15 cm and 20 cm for horizontal and height components,respectively.

Mixed Adjustment Algorithm for Part of the Coefficient Matrix with Uncertainty

WANG Zhizhong, SONG Yingchun, HE Lingli

2018, 47(9):  1171-1178.  doi:10.11947/j.AGCS.2018.20170344

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Uncertainty often exists in the process of measurement data acquiring,which affects the reliability and validity of parameter estimation.Based on uncertain mixed adjustment model,this paper applies the adjustment criterion,minimizing the sum of squares of random error and squares of uncertainty error,to study a new iteration algorithm to solve the adjustment model under the bound constrain of uncertainty.By the example,the estimation results of proposed method are compared with that of another relative method.The results show that the parameter calculation method presented in this paper is effective and feasible.Meanwhile,the method has satisfied applicability when the uncertainty is large.

A Method to Improve the Utilization Rate of Satellite Rays for Three-dimensional Water Vapor Tomography Using the ECMWF Data

ZHAO Qingzhi, YAO Yibin, YAO Wanqiang, CHEN Peng, WU Manyi

2018, 47(9):  1179-1187.  doi:10.11947/j.AGCS.2018.20170412

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In order to overcome the disadvantage of traditional tomography method which only uses the signals passing from the top boundary of research area for reconstructing of three-dimensional water vapor information,a novel method is proposed which improve the utilization rate of signals used based on the European Centre for Medium-range Weather Forecasts (ECMWF) data.By introducing the scale factor,the slant water vapor content which derived from the signals penetrated from the side face of research area is obtained and participating the establishment of observation equation.The observed GPS observation from the satellite positioning reference station network (SatRef) and the corresponding meteorological data are selected to validate the feasibility and accuracy of the proposed method by combing the radiosonde data of 45004 and the grid point data from ECMWF.Experimental result shows that the utilization rate of rays used and the coverage rate of voxels crossed by rays are increased by 55.16% and 16.46%,respectively.The root mean square error,mean absolute error and relative error calculated from the proposed method are superior to that of traditional method,when the radiosonde data and ECMWF data are regarded as the references.

Downward Continuation of Airborne Gravimetry Data Based on Improved Poisson Integral Iteration Method

LIU Xiaogang, SUN Zhongmiao, GUAN Bin, FAN Haopeng

2018, 47(9):  1188-1195.  doi:10.11947/j.AGCS.2018.20170569

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Airborne gravimetry is an effective technology to obtain the Earth's gravity field information of land and offing area in high precision and resolution quickly.Downward continuation is one of the key steps in airborne gravimetry data processing,and the quality of continuation results directly influence the further application of surveying data.Based on numerical analysis of the continuation models of traditional least squares method,improved least squares method and Tikhonov regularization method,and according to the basic characteristics of spherical harmonic function,the continuation models of Poisson integral iteration method and improved Poisson integral iteration method were proposed and deduced.For the testing area in this paper,the surveyed airborne and terrestrial gravimetry data prove that the precision of the new continuation models of Poisson integral iteration method and improved Poisson integral iteration method are equal.Compared with the continuation models of traditional least squares method and improved least squares method,of which the precision are improved about 15.26 mGal and 0.21 mGal,respectively.The precision of new continuation models are inferior to Tikhonov regularization method about 0.13 mGal.Therefore,the new continuation models proposed in this paper can not only be used to amend the ill-posed problem of the continuation model introduced by traditional Poisson integral discretization formula,but also be used to suppress the ill-posed problem of the continuation model itself.Therefore,the research achievements can be applied directly in the data processing of our country's airborne scalar and vector gravimetry.

Analysis of GNSS Postseismic Deformation of Wenchuan Earthquake

YU Jianshaneg, ZHAO Bin, TAN Kai, WANG Dongzhen

2018, 47(9):  1196-1206.  doi:10.11947/j.AGCS.2018.20170434

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Processing and analysis of 109 GNSS continuous stations and campaign stations after Wenchuan earthquake on both sides of the Longmen shan fault during the year of 1999-2015,we use the international high-precision data processing software to obtain the time series of horizonal coordinate for each site.Considering the effect of coseismic deformation of Lushan earthquake in 2013 and performing time series analysis,get the postseismic deformation field of 109 stations in the earthquake area during 2010-2015,maximum postseismic displacement in horizontal up to 5~7 cm in the epicenter near the upper falut.Based on the model of postseismic viscoelastic relaxation and searched by grid,inverted the best thickness of the middle to upper crustal elastic layer and the best coefficient of viscosity in viscoelastic layer of lower crust and upper mantle according to three different rupture models,and obtained the distribution of deformation from observation and simulation value of three different rupture models during 2010-2015.According to the parameters obtained by inversion of model 2,calculate the impact on crustal deformation in the surrounding area in next few decades after Wenchuan earthquake,the maximum cumulative postseismic deformation in 40 years during 2018-2058 up to 19 cm.

Spatio-temporal Urban Sprawl Monitoring and Analysis over Beijing-Tianjin-Hebei Urban Agglomeration during 1990—2015

NING Xiaogang, WANG Hao, LIN Xiangguo, CAO Yinxuan, DU Jun

2018, 47(9):  1207-1215.  doi:10.11947/j.AGCS.2018.20170414

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As an important indicator to access urbanization,the definition of urban boundary is of great importance of spatial-temporal urban sprawl monitoring and analysis.However,there are problems existed in urban boundary extraction currently,including lack of unified delimitation standards,inconsistent data sources,low or inadequate RS image resolutions,using construction land or impervious surfaces to replace urban area,etc.To solve the above-mentioned problems,a semi-automatic urban boundary extraction method based on high-resolution RS images and fundamental geoinformation data is proposed in this paper,which is referred to the concept of built-up area and the geographical distribution of urban area,and fully applied the spatial visualization characteristics of urban landscape and pattern from remote sensing images.By extracting the urban boundaries of 153 cities of Beijing-Tianjin-Hebei region in 1990,2002 and 2015 and their fundamental geoinformation data,the urbanization process in a quarter century of Beijing-Tianjin-Hebei is analyzed from the aspects of urban spatial-temporal sprawl process,urban spatial landscape and pattern changes,urban sprawl coordination,and occupied land types.The method proposed in the paper and the analysis results of urbanization process provide a great reference for urbanization monitoring and urban planning implementation and evaluation.

Object Detection in Remote Sensing Imagery with Multi-scale Deformable Convolutional Networks

DENG Zhipeng, SUN Hao, LEI Lin, ZHOU Shilin, ZOU Huanxin

2018, 47(9):  1216-1227.  doi:10.11947/j.AGCS.2018.20170595

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Traditional target detection methods based on sliding window search paradigm and hand-craft based features are difficult to be applied to the multi-class target detection of very-high-resolution remote sensing images. In this paper,we proposed a deformable convolutional networks based multi-class target detection method by introducing deformable convolution layer and deformable RoI (Region-of-Interest) pooling layer. Specially,our method consists of two sub networks:a region proposal network aims to predict candidate regions from several layers with different filter size,and a region classification network for discrimination and regression. The quantitative comparison results on the challenging NWPU VHR-10 data set,large-scale Google Earth images, GF-2 and JL-1 images show that our method is more accurate and robust than existing algorithms.

Vehicle Speed Detection by Multi-source Images from UAV

JIANG Shangjie, LUO Bin, HE Peng, YANG Guopeng, GU Yaping, LIU Jun, ZHANG Yun, ZHANG Liangpei

2018, 47(9):  1228-1237.  doi:10.11947/j.AGCS.2018.20170506

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Traffic plays a vital role in people's life and social economy.Vehicle speed detection is an important part of intelligent transportation system.This paper focus on the vehicle speed detection based on multi-source data from autonomous unmanned aerial vehicle (UAV).Firstly,we build a multi-source data acquisition system on UAV for visible image and thermal infrared image.Secondly,we utilize "You only look once" (YOLO),which is a deep learning framework for vehicle detection.Finally,we track the vehicle based on Kalman filter and calculated the vehicle speed according to the result of vehicle tracking.This paper adopts the UAV platform to increase the flexibility.While the use of multi-source data improves the accuracy of the vehicle detection and tracks the vehicle in different illumination.The result of experiments shows that the strategy is effective and robust,which provides an efficient and flexible monitoring mode for traffic management department.

Hyperspectral Image Classification by Combination of Spatial-spectral Features and Ensemble Extreme Learning Machines

GU Yu, XU Ying, GUO Baofeng

2018, 47(9):  1238-1249.  doi:10.11947/j.AGCS.2018.20170476

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To improve hyperspectral image classification accuracy,a classification method based on combination of spatial-spectral features and ensemble extreme learning machines is proposed in this paper.First,a spatial-spectral feature vector for each pixel is extracted using its neighboring information. Considering the strong correlation relationship between neighboring bands in a hyperspectral image,average grouping is performed for the extracted features,and a certain number of bands are first selected randomly from each interval and then combined to form a new feature with fewer dimensions.Extreme learning machine which can be trained fast is used to train a classifier.To improve the generalization performance of the learned model,several rounds of sampling are carried out based on ensemble learning theory,and several weak classifiers are trained and then combined to build a strong classifier using majority vote method.The classification experiments are performed using three typical hyperspectral image datasets,and the experimental results demonstrate that,the proposed algorithm can achieve preferable results compared with the state-of-the-art classifiers.It can achieve better classification accuracies when fewer training samples are used.The proposed algorithm has the advantages of few adjustable parameters,fast training speed,and high classification accuracy,and can be applied in many areas.

A Nonparametric Test Method for Identifying Significant Cross-outliers in Spatial Point Dataset

YANG Xuexi, DENG Min, SHI Yan, TANG Jianbo, LIU Qiliang

2018, 47(9):  1250-1260.  doi:10.11947/j.AGCS.2018.20170321

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In the field of geography,a spatial outlier is an object whose non-spatial attribute value is significantly different from the values of its spatial neighbors. Detection of spatial outliers will be helpful to uncover special geographical phenomenon,so it has become an important branch of spatial data mining.Although existing methods are able to measure spatial outlier factor,the significance of these outliers can not be evaluated in an objective way. Furthermore,the existing methods are mainly designed for single class dataset,without taking into account the interaction between different categories of dataset.In this study,a nonparametric test was developed to identify the significant cross-outliers in spatial point dataset.Firstly,a reasonable and stable spatial neighborhood is constructed for the primary dataset entitys using the constraint Delaunay triangulation.Then,using the number of reference dataset entitys falling in the spatial reference neighbor radius to measure the initial outlier factor.Constructed the support domain by α-Shape method,the null model is constructed based on spatial randomness process,and the significant spatial cross-outliers are identified by statistical test.Finally,the stability of the spatial cross-outlliers are evaluated by the living distance.Experimentson on both simulated and real-world datasets show that the proposed permutation test is effective for determining significant spatial cross-outliers in spatial point datasets.

A Point-of-interest Recommendation Method Based on Hawkes Process

ZHANG Guoming, WANG Junshu, JIANG Nan, SHENG Yehua

2018, 47(9):  1261-1269.  doi:10.11947/j.AGCS.2018.20170552

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Point-of-interest (POI) recommendation is a crucial personalized location service in LBSNs.To cope with the complexity and extreme sparsity of users check-in data,we proposed a context-aware collaborative filtering POI recommendation algorithm based on Hawkes process (HWCF).First,we analyzed users' behavior characteristics according to the geographic spatial clustering phenomenon of users' check-in POI,and filtered users' candidate POI.Then,we utilized Hawkes process to model candidate POI.Integrated different context information,such as spatial distance,spatial sequence transformation,temporal,users' preferences,POI popularity,etc.to compute the visiting probability of candidate POI for every user,and then obtained the top-k recommendation list by sorting the visiting probability.Finally,we discussed the range and adjustment of parameters in HWCF algorithm.Experimental results show that HWCF achieves better performance compared to other advanced POI recommendation algorithms.

Transformations among Topological Relation Representation Models for Regions with Holes Using the 25-intersection Method

WANG Zhangang, QU Honggang, WANG Xianghong

2018, 47(9):  1270-1279.  doi:10.11947/j.AGCS.2018.20160589

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A variety of topological relation representation models for complex regions with holes have been put forward nowadays.Establishing the connections among different models can give full play to the advantages of these models in the derivation and analysis of topological relations.Based on the point-set topology theory and region decomposition,six topological relation representation models were analyzed.Two 25-intersection (25I) Boolean matrix operators were defined and used for computing the binary topological relations between complex regions while the relations between the decomposed regions were known.Based on the operators,transformations among the description models were realized.Theoretical analysis proved that the relational matrix table and extended 9-intersection model have the same accurate expression of topological relations and can be transformed with each other,and so do the 4-tuple model and 25I model.Furthermore,the method of relational matrix table can be transformed to 25I model and classical 9-intersection model.The experimental analysis shows that our method can be used to link different topological relation representation models and derive topological relations between complex regions with holes.

Investigation on Underwater Positioning Stochastic Model Based on Sound Ray Incidence Angle

ZHAO Shuang, WANG Zhenjie, LIU Huimin

2018, 47(9):  1280-1289.  doi:10.11947/j.AGCS.2018.20170026

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The equal weight modelwidely used in underwater positioning is easy to implement.However,it does not meet with the reality and has an impact on the positioning accuracy.Aimed at this problem,combined with the underwater positioning reality,we take the effect of the underwater acoustic measurement error and the sound ray bending error into consideration.Based on the analysis of the parameter estimation properties on the condition of the incomplete stochastic model,we establish four stochastic models based on the sound ray incidence angle.Both the simulation data and practical data were used to test the effectiveness of our model.The results show that the established incidence angle stochastic models have advantages over the equal weight model,especially that the positioning result of using the segmental cosine model is the best.The positioning accuracy is the highest during the incidence angle within the scope of 40°~50°.The incidence angle stochastic model improve the positioning result of the traditional equal weight model.

Research on Key Technologies of BDS Precise Orbit Determination

ZHANG Rui

2018, 47(9):  1290-1290.  doi:10.11947/j.AGCS.2018.20170473

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Modeling and Methods of Service Relation for Land Cover Change Detection

XING Huaqiao

2018, 47(9):  1291-1291.  doi:10.11947/j.AGCS.2018.20170523

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Study of Determining the GOCE Satellite Gravity Field Based on Torus Approach

LIU Huanling

2018, 47(9):  1292-1292.  doi:10.11947/j.AGCS.2018.20170528

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Research on Real-time High Precision BeiDou Positioning Service System

ZHANG Yize

2018, 47(9):  1293-1293.  doi:10.11947/j.AGCS.2018.20170534

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Error Compensation and Reliability Analysis for Loitering Munition Integrated Navigation System

WU Youlong

2018, 47(9):  1294-1294.  doi:10.11947/j.AGCS.2018.20170543

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