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    20 November 2018, Volume 47 Issue 11
    Prism Algorithms for the Near-zone Direct and Indirect Topographic Effects
    MA Jian, WEI Ziqing
    2018, 47(11):  1429-1436.  doi:10.11947/j.AGCS.2018.20170369
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    It is necessary to calculate the direct effect on gravity and the indirect effects on the geoid and quasi-geoid when reducing the topography based on Helmert's second condensation method for solving boundary value problems. The traditional integration algorithms for the near-zone direct and indirect topographic effects arein the double integral form and give some approximate errors when taking the integral kernel at the center of the grid as the average of the grid integral kernel. Furthermore, the traditional integral algorithms for the direct and indirect effects have singularity in the innermost area, which increases the computational complexity. In this paper, the prism formulae of the near-zone direct and indirect effects are deduced, which improves the calculation accuracy on the one hand and simplifies the computation process by removing the singularity in the innermost area on the other hand. To overcome the planar approximation error of the prism models, the curvature of the earth can be taken into account. Finally, experimental results show that the prism algorithm for the topographic effect considering the earth's curvature is recommended when a high-accuracy geoid/quasi-geoid is required.
    Fast Realization of Ultra-high-degree Geopotential Model by Improved Least-squares Method
    TIAN Jialei, LI Xinxing, WU Xiaoping, XING Zhibin
    2018, 47(11):  1437-1445.  doi:10.11947/j.AGCS.2018.20170659
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    Using the least-squares method to solve the ultra-high-degree geopotential model is very difficult because this method needs to calculate massive data.In this paper,we first analyzed the characteristics of coefficient matrix and normal matrix based on the basic observation equation of geopotential model using the orthogonality of trigonometric function and surface coherence factor.Then,we reduced the matrix solution equation and designed the calculation and storage method of Legendre function based on normal matrix block diagonalization using the increment characteristic of "secondary M" during the process of solving normal matrix by coefficient matrix solution method.At last,the problems of storage and low computational efficiency of large matrix were solved by combining the equator symmetry characteristic of Legendre function,reduction of the matrix solution equation and design of the calculation and storage method of Legendre function.Through the experimental test,the improved method compared to traditional block diagonal method canimprove the efficiency by 300 times,by using this method we can solve ultra-high-degree geopotential model in ordinary PC,and the precision of the model has been improved by 5 orders of magnitude at least when compared with the numerical integral method.At the same time,the accuracy of the original data can be evaluated.
    Robust Gaussian Mixture Model for Mobile Robots' Vision-based Kinematical Localization
    CHENG Chuanqi, HAO Xiangyang, LI Jiansheng, HU Peng, ZHANG Xu
    2018, 47(11):  1446-1456.  doi:10.11947/j.AGCS.2018.20170649
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    In dynamic environments,the moving landmarks can make the accuracy of traditional vision-based localization worse or even failure.To solve this problem,a robust Gaussian mixture model for vision-based localization with dynamic landmarks is proposed.The motion index is added to the traditional graph-based vision-based localization model to describe landmarks' moving probability,changing the classic Gaussian model to Gaussian mixture model,which can reduce the influence of moving landmarks for optimization results.To improve the algorithm's robustness to noise,the covariance inflation model is employed in residual equations.The expectation maximization method for solving the Gaussian mixture problem is derived in detail,transforming the problem into classic iterative least square problem.Experimental results demonstrate that in dynamic environments,the proposed algorithm outperforms the traditional method both in absolute accuracy and relative accuracy,while maintains high accuracy in static environments.The proposed method can effectively reduce the influence of the moving landmarks in dynamic environments,which is more suitable for the autonomous localization of mobile robots.
    A Method of INS-aided Cycle-slip Detection for PPP
    LI Leilei, YANG Sheng, DING Xuewen, CHEN Hua, CHEN Qusen, LIU Jingbin, SUN Hongxing
    2018, 47(11):  1457-1465.  doi:10.11947/j.AGCS.2018.20170315
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    Due to the problem of high receiver dynamics, low satellite elevation, or the obstruction along the signal path, the carrier phase measurements in PPP/INS are often interrupted. Cycle slip will reduce the accuracy of positioning and may force the ambiguities to re-initialize that normally take 10 minutes or more. A new cycle-slip detection method for PPP is presented here utilizing the high-precision INS information, instead of pseudoranges to remove satellites geometric distances in wide-lane combination. This new algorithm is tested in a vehicle experiment and the results show that it has excellent sensitivity to cycle slip even small ones. By combination with the GF method, this method can detect the isoperimetric and special cycle slip pairs (such as 5/4, 9/7) with high accuracy. It can also be used for real-time cycle slip detection.
    Analysis on the Driving Factors of Urban Expansion Policy Based on DMSP/OLS Remote Sensing Image
    WANG Taoyang, ZHANG Guo, LI Peiran, LI Fangting, GUO Xueyao
    2018, 47(11):  1466-1473.  doi:10.11947/j.AGCS.2018.20170353
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    The speed and direction of urban expansion has become the focus of social concern, and it is a research hotspot in recent years that using night-light remote sensing for urban expansion driving force analysis of the causes. The average annual Chinese regional night-light image data is adopted that obtained by DMSP satellites. First of all, relative radiation correction is performed for 1992-2012, a total of 21 years of time-dependent night-light images. Secondly urban built area is extracted by empirical threshold method, and accuracy is verified through the Landsat images. Finally, the econometric model is introduced, the political cycle of the administrative officials of the prefecture-level city is the explanatory variable. It is analyzed the policy driving factors of the expansion of the prefecture-level cities from 1992 to 2012. Through the analysis of this article, we can see that the change of the political cycle of the administrative officials has a significant impact on the direction of urban expansion.
    Investigation on GNSS Lever Arms and IMU Boresight Misalignment Calibration of Domestic Airborne Wide-field Three CCD Camera
    WANG Tao, ZHANG Yan, ZHANG Yongsheng, MO Delin, ZHOU Liya
    2018, 47(11):  1474-1486.  doi:10.11947/j.AGCS.2018.20170679
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    Focusing on the first domestic developed airborne three line CCD camera (GFXJ), it is carried out that the innovative investigation work on GNSS lever arms and IMU boresight misalignment calibration of GFXJ camera. Firstly, a brief introduction is given on the imaging properties of GFXJ camera. Then, the GNSS level arms calibration model and IMU boresight misalignment calibration model are built for GFXJ camera after detailed investigation. Meanwhile, the iterative two-step calibration scheme is put forward for the GNSS level arms and IMU boresight misalignment calibration of GFXJ camera. Finally, multiple sets of flight data are captured under the support of the national Songshan remote sensing comprehensive testfield. Through the block adjustment and calibration experiments of these sets of imaging data, it verifies the correctness and the efficiency of proposed GNSS lever arms calibration model and IMU boresight misalignment calibration model, and also demonstrates the reliability and practicability of the iterative two-step calibration scheme for GFXJ camera. The proposed calibration scheme can significantly enhance the geometric positioning accuracy of GFXJ camera. Using the GNSS level arms and the IMU boresight misalignment calibration values, the uncontrolled positioning accuracy of GFXJ camera can be significantly improved. Aided with several control points for re-block adjustment, the planar positioning accuracy of GFXJ camera can fulfill the accuracy requirements of 1:1000 scale mapping, but there still exists a little gap between its height positioning accuracy and the 1:1000 scale mapping requirements. The camera is still in the calibration flight stage, its geometric performance can be further improved after product approval. Moreover, the GNSS lever arms calibration model, the IMU boresight misalignment calibration model, and the iterative two-step calibration scheme put forward in the paper can be applied to calibration work for other airborne CCD cameras.

    Influence of Range Gate Width on Detection Probability and Ranging Accuracy of Single Photon Laser Altimetry Satellite
    LI Guoyuan, HUANG Jiapeng, TANG Xinming, HUANG Genghua, ZHOU Shihong, ZHAO Yanming
    2018, 47(11):  1487-1494.  doi:10.11947/j.AGCS.2018.20170469
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    The influence of the single photon laser altimeter range-gate width on the detection probability and ranging accuracy is discussed and analyzed, according to the LiDAR equation, single photon detection equation and the Monte Carlo method to simulate the experiment. The simulated results show that the probability of detection is not affected by the range gate, while the probability of false alarm is relative to the gate width. When the gate width is 100 ns, the ranging accuracy can accord with the requirements of satellite laser altimeter. But when the range gate width exceeds 400 ns, ranging accuracy will decline sharply. The noise ratio will be more as long as the range gate to get larger, so the refined filtering algorithm during the data processing is important to extract the useful photons effectively. In order to ensure repeated observation of the same point for 25 times, according to the parameters of ICESat-2, we deduce the quantitative relation between the footprint size, footprint, and the frequency repetition. The related conclusions can provide some reference for the design and the development of the domestic single photon laser altimetry satellite.
    Calibration of Airborne Interferometric SAR with Single Corner Reflector in Two Converse Flights
    WANG Bingnan, XIANG Maosheng, JIANG Shuai, FU Xikai
    2018, 47(11):  1495-1505.  doi:10.11947/j.AGCS.2018.20170450
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    Quite a few corner reflectors are essential for interferometric SAR in high precision terrain mapping applications,which limits its application in surveying and mapping industry.In this paper,we present a calibration algorithm of airborne interferometric SAR using single corner reflector in two converse flights.Firstly,based on principle of SAR interferometry,a three-dimensional calibration model considering horizontal and elevation positioning is constructed.Then several characteristic parameters which affect 3D location are analyzed and reduced to three parameters successfully.Finally,we extracted a number of tie points from two groups of complex image pairs in two converse flights by SIFT algorithm.New calibration functions can be developed from the tie points,which helps reduce number of control points.Real data experiments results confirmed the validity and rationality of the proposed algorithm.
    Landmark Matching Method about Pointing to the Ground of Three-axis Stabilization Geostationary Remote Sensing Satellite
    DING Lu, TONG Xiaochong, QIN Zhiyuan, LAI Guangling
    2018, 47(11):  1506-1517.  doi:10.11947/j.AGCS.2018.20170600
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    Geostationary remote sensing satellite is relatively static to the earth.However,because of the influences suffered from inner factors and outer environment,an error of geometric would be happened to satellite's pointing to the ground,and it will cause a large position error on the ground,so that,an effective modification is needed.This paper proposed a set calculation method of pointing to the ground based on landmark matching,which centered on the problem of pointing to the ground when the three-axis stabilization geostationary remote sensing satellite was shooting the earth disk.This method mainly solved the following problems:the generator method of landmark data which was the datum reference,robust matching method between image and landmark,the calculation method of pointing to the ground based on error elimination,and so on.The experiment showed that,this set of method had superior accuracy and stability in solving the error of pointing to the ground of geostationary remote sensing image.This technique had been applied in the online processing of related satellite data in our country.
    Watermarking Algorithm Applying to Small Amount of Vector Geographical Data
    TONG Deyu, ZHU Changqing, REN Na
    2018, 47(11):  1518-1525.  doi:10.11947/j.AGCS.2018.20170741
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    Aiming at the copyright protection especially for small amount of vector data,a watermarking algorithm based on compressive sensing and multi-segment quantization modulation have been proposed in this paper.In the procedure of watermark generation,binary copyright image is divided into blocks and measured by compressive sensing method to reduce the watermark redundancy.Measured results are then modulated into four values to reduce the watermark length and ensure the watermark recovery.In watermark embedding and detection,the principle of multi-segment modulation on the angle is studied by establishing the mapping relationship between watermark bit and modulation segment index.Hence this watermarking principle enables each vertex to carry more watermark bits in a robust way.Experiments have been conducted to verify the effectiveness of the proposed watermarking algorithm.By using the proposed algorithm,a binary copyright image is able to be embedded into the small amount of vector data,which consists of only 100 vertexes,and can be extracted clearly.The experiments also reveal that the watermark capacity of the proposed algorithm achieves above 7 bit for each vertex,which is higher than the comparison algorithms.Regarding the algorithms robustness,the proposed watermarking algorithm shows its superior robustness against attacks including vertex insertion,vertex deletion,vertex sorting,translation,rotation and scaling.In summary,the contradiction between high watermark capacity and small data volume has been solved by the proposed watermarking algorithm.
    Hierarchical Area Partitioning Method of Urban Road Networks Matching
    HUANG Bohua, ZHONG Wei, ZHAI Renjian, ZHOU Qing
    2018, 47(11):  1526-1536.  doi:10.11947/j.AGCS.2018.20170699
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    In view of the "Node-Arc" data model of road network in the aspect of structured expressing the deficiencies,the hierarchical area partitioning of road network based on the principle of stroke,which made road network space structure characteristics of the expression with the hierarchical feature was designed.Based on road hierarchy and connected relationship with the area domain boundaries,the road in the area was hierarchically divided.A hierarchical model was established based on "whole-part-object" data model.Finally,the model of urban road network matching is proposed,which used consistency evaluation model selected matching objects from high-grade road to the low-level road.The experiment results indicated that the method was suitable to solve the road matching problem with typical urban features.
    Research and Evaluation on Key Technological Target System for Marine and Airborne Gravity Surveys
    HUANG Motao, LIU Min, WU Taiqi, LU Xiuping, DENG Kailiang, ZHAI Guojun, OUYANG Yongzhong, CHEN Xin
    2018, 47(11):  1537-1548.  doi:10.11947/j.AGCS.2018.20170617
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    Technological standard is an important scientific basis for marine and airborne gravity surveys. In accordance with the lack of the present specifications to reflect the trend of the times for marine and airborne gravity surveys,a detail analysis and research is made on key targets, such as the density of surveying line layout, survey accuracy, space resolution, zero drift and dynamic repeatability of air-sea gravimeter,etc. An evaluation system of survey accuracy targets including root mean square of errors(RMS),systematic error and mean error for marine and airborne gravity surveys is suggested. And an evaluation system of stability targets including calibration accuracy of scale value, total month zero drift, RMS of nonlinear month drift and limited deviation of nonlinear month drift is proposed. The methods of testing and evaluating the above technological targets are introduced. And some key mathematic models about reduction of observed values for marine gravity survey,Eötvös correction for airborne gravimetry,platform tilt correction and evaluation of survey accuracy for air-sea-borne gravimetry are analyzed and modified. The obtained conclusions provide useful theoretical support for the revision of existing specifications for future civil-military inosculation of marine and airborne gravity surveys.
    Second CUBE Filtering Algorithm and Its Application in Sounding Data Processing of Slope Riprap Area
    ZHENG Yongxin, ZHANG Hongmei, ZHAO Jianhu
    2018, 47(11):  1549-1557.  doi:10.11947/j.AGCS.2018.20170354
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    Traditional CUBE (combined uncertainty bathymetry estimation) filter generally fails to estimate the depth of the water accurately, and produces blur terrain feature in underwater slope riprap area by the multi-beam sounding data filtering with poor ability to remove gross error.Based on the sounding data characteristics of slope riprap area, a secondary CUBE filtering algorithm is proposed. The key idea is to estimate the plane position and depth synchronously, taking account of the transfer model of plane and water depth uncertainty related to terrain gradient. It is based on the second depth estimation model which considers geometric gradient and an optimization method of reference depth to accurately estimate the depth of water in underwater riprap areas and to detect gross error automatically.A set of meaningful experiments are also presented. And the experimental results have shown that the proposed method provides an automatic and accurate elimination for gross error. Specifically, the accuracy of the proposed algorithm is a few times higher than that of the traditional CUBE. It also demonstrates that the proposed filter shows superiority in preserving terrain features with better efficiency and robustness.
    Research on Models and Methods of Indoor Location Map Data Processing
    SUN Weixin
    2018, 47(11):  1558-1558.  doi:10.11947/j.AGCS.2018.20170647
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    Research on Regional Geological Structure, Semantic Parsing and Object Modeling
    HE Handong
    2018, 47(11):  1559-1559.  doi:10.11947/j.AGCS.2018.20170687
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    Research on Effects of Unmodeled Errors and Environmental Loading on GPS Coordinate Time Series
    DENG Liansheng
    2018, 47(11):  1560-1560.  doi:10.11947/j.AGCS.2018.20170684
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    QTM-based Spherical Voronoi Diagram Generating Algorithms and Its Application
    WANG Lei
    2018, 47(11):  1561-1561.  doi:10.11947/j.AGCS.2018.20170717
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    Study on Track Precise Inspection and Adjustment as Well as Its Regularity Optimization for High-speed Railways
    LI Yangtenglong
    2018, 47(11):  1562-1562.  doi:10.11947/j.AGCS.2018.20170722
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