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    20 July 2015, Volume 44 Issue 7
    Analysis of Tidal Data for Dagang Tidal Gauge and Study of the Changes for the National Height Datum
    WU Fumei, WEI Ziqing, LI Yingchun
    2015, 44(7):  709-716.  doi:10.11947/j.AGCS.2015.20140110
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    The main tides affecting Dagang sea level are analyzed and the national height datum is studied by analyzing 1980—2011 hourly tidal data and 1952—2007 monthly mean tidal data. Firstly, the frequencies and amplitudes of main tides including 180 short-period tides and 6 long-period tides are gained by the Fouirer transform. Then the actual amplitudes and their variations of main tides are obtained by the harmonic analysis of the 1980—2011 hourly tidal data, and the changes with about 19 year period can easily be found in the amplitudes of Q1O1M2K1、K2. And then the changes of the mean sea level at Dagang tidal gauge defining national height datum during the period of 1952—2011 are studied by the harmonic analysis and the shifting average of 18.61 year tidal heights. The results of these methods show that the mean sea level at Dagang tidal gauge descended with the speed of 1.07 mm/a and 0.76 mm/a respectively during 1952—1980, and that it ascended with the speed of 1.59 mm/a and 1.62 mm/a respectively during 1980—2011. And finally the difference of 0.14 cm is achieved by the shifting average of 18.61 year tidal heights for 1985 National Height Datum.
    Ionospheric Cycle Slip Processing in Triple-frequency GNSS
    HUANG Lingyong, ZHAI Guojun, OUYANG Yongzhong, XU Guangxiu, LI Kaifeng, HUANG Xianyuan, FAN Long
    2015, 44(7):  717-725.  doi:10.11947/j.AGCS.2015.20140348
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    A new method based on three linear independence geometry-free and ionosphere-free (GIF) combinations to detect and repair cycle-slip is advanced to finishing the cycle slip processing under the higher ionospheric activity. In order to ensure that the cycle slip correction is accurate, the repair value is validated by a second-order, time-difference phase ionospheric residual (STPIR) combination. And then, this method is validated and analyzed by using the triple-frequency data with higher ionospheric error. The experiment results show that this method can nearly detect and repair all the cycle slip except several insensitive cycle slip under high ionospheric activity. So this method can be used to cycle slip procession in triple-frequency precise point position and other un-differenced dynamic navigation and position.
    Accuracy Assessment and Analysis for GPT2
    YAO Yibin, CAO Na, XU Chaoqian, YANG Junjian
    2015, 44(7):  726-733.  doi:10.11947/j.AGCS.2015.20140356
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    GPT(global pressure and temperature) is a global empirical model usually used to provide temperature and pressure for the determination of tropospheric delay, there are some weakness to GPT, these have been improved with a new empirical model named GPT2, which not only improves the accuracy of temperature and pressure, but also provides specific humidity, water vapor pressure, mapping function coefficients and other tropospheric parameters, and no accuracy analysis of GPT2 has been made until now. In this paper high-precision meteorological data from ECWMF and NOAA were used to test and analyze the accuracy of temperature, pressure and water vapor pressure expressed by GPT2, testing results show that the mean Bias of temperature is -0.59℃, average RMS is 3.82℃; absolute value of average Bias of pressure and water vapor pressure are less than 1 mb, GPT2 pressure has average RMS of 7 mb, and water vapor pressure no more than 3 mb, accuracy is different in different latitudes, all of them have obvious seasonality. In conclusion, GPT2 model has high accuracy and stability on global scale.
    Comparison of Ionosphere-free, Uofc and Uncombined PPP Observation Models
    LI Bofeng, GE Haibo, SHEN Yunzhong
    2015, 44(7):  734-740.  doi:10.11947/j.AGCS.2015.20140161
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    GNSS precise point positioning (PPP) has become the research hotspot in the most recent years due to its capability of obtaining precise position with single receiver. Usually, three models are used in PPP, that is,uncombined model, Uofc model and ionosphere-free combination model. The relationships between the these models are described in detail in this paper. On the one hand, it is clarified that the uncombined model is equivalent to the Uofc model and both of them are better than the ionosphere-free model in the sense of ambiguity resolution. On the other hand, in comparison with the Uofc model that eliminates the ionosphere delay by using the equivalence principle, the uncombined model that takes the ionosphere delay as the parameter has its advantage that it can provide the users with the prior constrained conditions for the ionosphere. As a result, the model can be converted to the ionosphere-weighted model easily. In the circumstance of fixing the wide-lane, when comparing with the ionosphere-free model by using ambiguity dilution of precision (ADOP) from the aspect of fixing ambiguity, Uofc model has many advantages such as small noise, origin information preserving etc.,while the ionosphere-weighted model can improve the ambiguity resolution significantly when the high precise prior ionosphere information is available.

    Great Ellipse Route Planning Based on Space Vector
    LIU Wenchao, BIAN Hongwei, WANG Rongying, WEN Chaojiang
    2015, 44(7):  741-746.  doi:10.11947/j.AGCS.2015.20130799
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    Aiming at the problem of navigation error caused by unified earth model in great circle route planning using sphere model and modern navigation equipment using ellipsoid mode, a method of great ellipse route planning based on space vector is studied. By using space vector algebra method, the vertex of great ellipse is solved directly, and description of great ellipse based on major-axis vector and minor-axis vector is presented. Then calculation formulas of great ellipse azimuth and distance are deduced using two basic vectors. Finally, algorithms of great ellipse route planning are studied, especially equal distance route planning algorithm based on Newton-Raphson(N-R) method. Comparative examples show that the difference of route planning between great circle and great ellipse is significant, using algorithms of great ellipse route planning can eliminate the navigation error caused by the great circle route planning, and effectively improve the accuracy of navigation calculation.
    Nonlinear Adjustment Model with Integral and Its Application to Super Resolution Image Reconstruction
    ZHU Jianjun, FAN Donghao, ZHOU Cui, ZHOU Jinghong
    2015, 44(7):  747-752.  doi:10.11947/j.AGCS.2015.20140204
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    The process of super resolution image reconstruction is such a process that multiple observations are taken on the same target to obtain low resolution images, then the low resolution images are used to reconstruct the real image of the target, namely high resolution image. This process is similar to that in the field of surveying and mapping, in which the same target is observed repeatedly and the optimal values is calculated with surveying adjustment methods. In this paper, the method of surveying adjustment is applied into super resolution image reconstruction. A integral nonlinear adjustment model for super resolution image reconstruction is proposed at first. And then the model is parameterized with a quadratic function. Finally the model is solved with the least squares adjustment method. Based on the proposed adjustment method, the specific strategy of image reconstruction is presented. This method for super resolution image reconstruction can make quantitative analysis of the results, and avoid successfully ill-condition problem, etc. The results show that, compared to the traditional method of super resolution image reconstruction, this method has greatly improved the visual effects, and the PSNR and SSIM has also greatly improved, so the method is reliable and feasible.
    Edge Detection of PolSAR Image Based on Stochastic Distance
    WANG Qing, ZENG Qiming, ZHANG Haizhen, JIAO Jian
    2015, 44(7):  753-760.  doi:10.11947/j.AGCS.2015.20130810
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    A new edge detection methodology in PolSAR images is proposed, which is based on stochastic distance in the statistical theory and combined with complex Wishart distribution. Its main principle is inspired from the phenomenon that stochastic distance of two classes separated by an edge is closely related to the edge direction and the contrast of two classes. Simulation experiments are carried out to analyze the performance of the proposed methods. Results prove that methods have better capabilities in edge orientation and edge positioning than common used methods. Then, the proposed detection procedure is tested on a simulated PolSAR image with the complex Wishart distribution, as well as an airborne fully polarimetric SAR image.

    Registration of Aerial Image with Airborne LiDAR Data Based on Plücker Line
    SHENG Qinghong, CHEN Shuwen, FEI Lijia, LIU Jianfeng, WANG Huinan
    2015, 44(7):  761-767.  doi:10.11947/j.AGCS.2015.20140123
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    Registration of aerial image with airborne LiDAR data is a key to feature extraction. A registration model based on Plücker line is proposed. The relative position and attitude relationship between the conjugate lines in LiDAR and image is determined based on Plücker linear equation, which describes line transformation in space, then coplanarity condition equation is established. Finally, coordinate transformation between image point and corresponding LiDAR point is achieved by the spiral movement of Plücker lines in the image. The registration model of Plücker linear coplanarity condition equation is simple, and jointly describes the rotation and translation to avoid coupling error between them, so the accuracy is approved. This research provides technical support for high-quality earth spatial information acquisition.
    Phase Grouping Line Extraction Algorithm Using Overlapped Partition
    WANG Jingxue, ZHU Qing, ZHANG Yunsheng, HU Han
    2015, 44(7):  768-774.  doi:10.11947/j.AGCS.2015.20140234
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    Aiming at solving the problem of fracture at the discontinuities area and the challenges of line fitting in each partition, an innovative line extraction algorithm is proposed based on phase grouping using overlapped partition. The proposed algorithm adopted dual partition steps, which will generate overlapped eight partitions. Between the two steps, the middle axis in the first step coincides with the border lines in the other step. Firstly, the connected edge points that share the same phase gradients are merged into the line candidates, and fitted into line segments. Then to remedy the break lines at the border areas, the break segments in the second partition steps are refitted. The proposed algorithm is robust and does not need any parameter tuning. Experiments with various datasets have confirmed that the method is not only capable of handling the linear features, but also powerful enough in handling the curve features.

    Hyperspectral Image Classification Based on the Combination of Spatial-spectral Feature and Sparse Representation
    YANG Zhaoxia, ZOU Zhengrong, TAO Chao, TIAN Yanping, HE Xiaofei
    2015, 44(7):  775-781.  doi:10.11947/j.AGCS.2015.20140207
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    In order to avoid the problem of being over-dependent on high-dimensional spectral feature in the traditional hyperspectral image classification, a novel approach based on the combination of spatial-spectral feature and sparse representation is proposed in this paper. Firstly, we extract the spatial-spectral feature by reorganizing the local image patch with the first d principal components(PCs) into a vector representation, followed by a sorting scheme to make the vector invariant to local image rotation. Secondly, we learn the dictionary through a supervised method, and use it to code the features from test samples afterwards. Finally, we embed the resulting sparse feature coding into the support vector machine(SVM) for hyperspectral image classification. Experiments using three hyperspectral data show that the proposed method can effectively improve the classification accuracy comparing with traditional classification methods.

    Rapidly 3D Texture Reconstruction Based on Oblique Photography
    ZHANG Chunsen, ZHANG Weilong, GUO Bingxuan, LIU Jianchen, LI Ming
    2015, 44(7):  782-790.  doi:10.11947/j.AGCS.2015.20140341
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    This paper proposes a city texture fast reconstruction method based on aerial tilt image for reconstruction of three-dimensional city model. Based on the photogrammetry and computer vision theory and using the city building digital surface model obtained by prior treatment, through collinear equation calculation geometric projection of object and image space, to obtain the three-dimensional information and texture information of the structure and through certain the optimal algorithm selecting the optimal texture on the surface of the object, realize automatic extraction of the building side texture and occlusion handling of the dense building texture. The real image texture reconstruction results show that: the method to the 3D city model texture reconstruction has the characteristics of high degree of automation, vivid effect and low cost and provides a means of effective implementation for rapid and widespread real texture rapid reconstruction of city 3D model.

    An Improved Algorithm Based on Minimum Spanning Tree for Multi-scale Segmentation of Remote Sensing Imagery
    LI Hui, TANG Yunwei, LIU Qingjie, DING Haifeng, JING Linhai
    2015, 44(7):  791-796.  doi:10.11947/j.AGCS.2015.20140060
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    As the basis of object-oriented information extraction from remote sensing imagery,image segmentation using multiple image features,exploiting spatial context information, and by a multi-scale approach are currently the research focuses. Using an optimization approach of the graph theory, an improved multi-scale image segmentation method is proposed. In this method, the image is applied with a coherent enhancement anisotropic diffusion filter followed by a minimum spanning tree segmentation approach, and the resulting segments are merged with reference to a minimum heterogeneity criterion.The heterogeneity criterion is defined as a function of the spectral characteristics and shape parameters of segments. The purpose of the merging step is to realize the multi-scale image segmentation. Tested on two images, the proposed method was visually and quantitatively compared with the segmentation method employed in the eCognition software. The results show that the proposed method is effective and outperforms the latter on areas with subtle spectral differences.

    Steering Angle Function Algorithm of Morphing of Residential Area
    XIE Tian, LI Jingzhong
    2015, 44(7):  797-804.  doi:10.11947/j.AGCS.2015.20140333
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    A residential area feature morphing method based on steering angle function is presented. To residential area with the same representation under two different scales,transforming the representation of the residential area polygon from vector coordinates to steering angle function,then using the steering angle function to match,and finding out the similarity and the differences between the residential areas under different scale to get the steering angle function of the the residential areas under any middle scale,the final,transforming the middle scale steering angle function to vector coordinates form,and get the middle shape interpolation of the the residential area polygon.Experimental results show:the residential area morphing method by using steering angle function presented can realize the continuous multi-scale representation under the premise of keeping in shape for the residential area with the rectangular boundary features.

    A Field Source-strength Method for Interaction Scenario in Network Space of Metropolitan
    HE Jianhua, LI Chun, LIU Yaolin, YU Yan
    2015, 44(7):  805-812.  doi:10.11947/j.AGCS.2015.20140266
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    With the collaborative development of region, spatial interaction has become a hotspot issue in geography research. A scenario analysis model of urban multidimensional interaction was proposed based on geography spatial data field. Where the urban clustering area was viewed as a geography spatial data field. While the intercity spatial interactions were considered as field strength in the model. Then Wuhan metropolitan area was taken as a case to study intercity spatial interaction and its dynamics. The results indicates that the intercity spatial interaction is infirmness and its spatial pattern showing “one nuclear and multitude weak”, eastern interaction stronger than the west. Since 2006, effected by the policy of “1+8 City Circle of Wuhan”, the interaction has been reinforced and the integration process has been promoted effectively in recent years.

    A Quantitative Calculation Method of Spatial Direction Similarity Based on Direction Relation Matrix
    CHEN Zhanlong, ZHOU Lin, GONG Xi, WU Liang
    2015, 44(7):  813-821.  doi:10.11947/j.AGCS.2015.20140198
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    This article introduces a new model for direction relations between spatial objects at multiple scales and a corresponding similarity assessment method. The model is an improvement of direction relation matrix, which quantitatively models direction relations on object scale, and by means of the solution of the Transportation Problem to solve the minimum conversion cost between direction matrices, namely distance between a pair of matrices, thus quantified the difference between a pair of directions, finally obtain the similarity values between arbitrary pairs of spatial objects and compare the results. Experiments on calculating similarity between objects at different scales show that the presented method is efficient, accurate, and capable of obtaining results consistent with human cognition.

    Key Techniques for Dynamic Updating of National Fundamental Geographic Information Database
    WANG Donghua, LIU Jianjun
    2015, 44(7):  822-825.  doi:10.11947/j.AGCS.2015.20150089
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    One of the most important missions of fundamental surveying and mapping work is to keep the fundamental geographic information fresh. In this respect, National Administration of Surveying, Mapping and Geoinformation has launched the project of dynamic updating of national fundamental geographic information database since 2012, which aims to update 1:50 000, 1:250 000 and 1:1 000 000 national fundamental geographic information database continuously and quickly, by updating and publishing once a year. This paper introduces the general technical thinking of dynamic updating, states main technical methods, such as dynamic updating of fundamental database, linkage updating of derived databases, and multi-tense database management and service and so on, and finally introduces main technical characteristics and engineering applications.

    A Study on Key Technology of High Precision GPS Monitoring for Geological Hazard
    WANG Li
    2015, 44(7):  826-826.  doi:10.11947/j.AGCS.2015.20150045
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