Loading...

Table of Content

    20 March 2015, Volume 44 Issue 3
    Discussions on the Attributes of Cartography and the Value of Map
    WANG Jiayao, CHENG Yi
    2015, 44(3):  237-241.  doi:10.11947/j.AGCS.2015.20140406
    Asbtract ( )   HTML   PDF (882KB) ( )  
    References | Related Articles | Metrics
    Cartography and map are all very important to topography and geography. Experts and scholars in different historical periods have different views of the attributes of cartography and the value of map. The paper discussed the science attribute, technology attribute and engineering attribute of cartography, summarized the value of map from science, society, jurisprudence and military aspects. It will be helpful to understand the basic attributes of cartography and the value of map, promote the sustained and healthy development of them.
    An Improved Global Zenith Tropospheric Delay Model
    YAO Yibin, HU Yufeng, YU Chen
    2015, 44(3):  242-249.  doi:10.11947/j.AGCS.2015.20140089
    Asbtract ( )   HTML   PDF (2711KB) ( )  
    References | Related Articles | Metrics
    The time resolution of GZTD model developed by Yao[16] is 24 hours. To further improve the time resolution of GZTD model, we used the time series of global 4D-grid ZTD from 2002 to 2009, provided by GGOS atmosphere, to construct model according to the 6 hours resolution, and then calculated the ZTD at any time using the cubic spline interpolation method. Thus we developed an improved higher time resolution (6h) GZTD model (GZTD-6h). Analyzing the inner coincidence of two models comparatively, we found that GZTD-6h model (bias: 0.17 cm, RMS: 3.9 cm) performs better than GZTD model (bias: 0.17 cm, RMS: 4.4 cm). Using ZTD time series from global International GNSS Service (IGS) sites to analyze outer coincidence, the statistical results shows that GZTD-6h model (bias:-0.22 cm, RMS: 4.05 cm) improves significantly, compared with GZTD model (bias:-0.45 cm, RMS: 4.51 cm).
    Convergence Time and Positioning Accuracy Comparison between BDS and GPS Precise Point Positioning
    ZHANG Xiaohong, ZUO Xiang, LI Pan, PAN Yuming
    2015, 44(3):  250-256.  doi:10.11947/j.AGCS.2015.20130771
    Asbtract ( )   HTML   PDF (2640KB) ( )  
    References | Related Articles | Metrics
    BDS/GPS data from MGEX were processed by TriP 2.0 software developed at Wuhan University. Both static and kinematic float PPP are tested by adopting precise satellite orbits and clocks provided by Research Center of GNSS, Wuhan University. The results show that the convergence time of BDS static PPP is about 80min while kinematic PPP is about 100min. For 3h observations, static positioning accuracy of 5 cm and kinematic positioning accuracy of 8 cm in horizontal, about 12 cm in vertical can be achieved. Similar to GPS PPP, precision in east component is worse than north. At present, BDS PPP needs longer convergence time than GPS PPP to reach an absolute positioning accuracy of cm~dm due to the lack of global tracking stations and the limited accuracy of orbit and clock products.
    Bright-star Recognition Algorithm and Its Application in Astronomical Azimuth Determination
    ZHAN Yinhu, ZHENG Yong, ZHANG Chao, LI Zhuyang, ZHANG Zhongkai
    2015, 44(3):  257-263.  doi:10.11947/j.AGCS.2015.20130557
    Asbtract ( )   HTML   PDF (1823KB) ( )  
    References | Related Articles | Metrics
    A novel bright-star identification algorithm is presented using the time series of vertical angle and horizontal angle velocity observed by the total station. The algorithm can distinguish planets from the starry background with automatically computing for the horizontal coordinates of the observed target. Based on the investigation of measurement errors, the matching thresholds and the effective matching strategy are given. Tests results with simulated and actual measurements show that the success rate of identification can be up to 100%, which is much higher than the existing algorithm. Then the identification algorithm is applied to the astronomical azimuth determination with the measurements of some bright stars and planets and the resulting precision and accuracy are 1.6" and 2.0", respectively. Finally, it is pointed that multi-star observations can improve the accuracy of the astronomical orientation by effectively removing the impact of errors of station coordinates. The presented orientation method can be extended to cloudy or haze weather when only few visible bright stars can be observed.
    An Analysis of the Applicability of Slepian Function in Analyzing Lunar Local Gravity Field
    SUN Xuemei, LI Fei, YAN Jianguo, HAO Weifeng
    2015, 44(3):  264-273.  doi:10.11947/j.AGCS.2015.20130728
    Asbtract ( )   HTML   PDF (20862KB) ( )  
    References | Related Articles | Metrics

    Based on a detailed analysis of the Slepian function, the advantages and disadvantages of the application of the Slepian function in computing lunar local gravity model, local power spectrum combined with the CEGM02 model and local admittance and correlation based on CEGM02, SGM150j, LP150Q and GRAIL660 were analyzed in this paper. It turns out that the local orthogonal Slepian function shows obvious advantages in modeling lunar local gravity field. In the application of power spectrum, the method of Slepian model shows a much wider, credible and reliable bandwidth but brings greater uncertainty in high degrees with the abnormal signal on the cap edge. On the contrary, the local power spectrum curve of Slepian window reflects the relationship between local gravity and the whole moon, but the spectral curve shows a narrow reliable bandwidth and significant errors in low degrees. Local admittance and correlation of four gravity models shows small difference in low orders but obvious difference as the orders get higher.

    Multi-image Matching of Airborne SAR Imagery by SANCC
    DING Hao, ZHANG Jixian, HUANG Guoman, ZHU Jianjun
    2015, 44(3):  274-281.  doi:10.11947/j.AGCS.2015.20140257
    Asbtract ( )   HTML   PDF (6037KB) ( )  
    References | Related Articles | Metrics
    In order to improve accuracy of SAR matching, a multi-image matching method based on sum of adaptive normalized cross-correlation (SANCC) is proposed. It utilizes geometrical and radiometric information of multi-baselinesynthetic aperture radar (SAR)images effectively. Firstly, imaging parameters, platform parameters and approximate digital surface model (DSM) are used to predict matching line. Secondly, similarity and proximity in Gestalt theory are introduced to SANCC, and SANCC measures of potential matching points along the matching line are calculated. Thirdly, multi-image matching results and object coordinates of matching points are obtained by winner-take-all (WTA) optimization strategy. The approach has been demonstrated with airborne SAR images acquired by a Chinese airborne SAR system (CASMSAR system). The experimental results indicate that the proposed algorithm is effective for providing dense and accuracy matching points, reducing the number of mismatches caused by repeated textures, and offering a better solution to match in poor textured areas.
    Hierarchical Outlier Detection for Point Cloud Data Using a Density Analysis Method
    ZHU Junfeng, HU Xiangyun, ZHANG Zuxun, XIONG Xiaodong
    2015, 44(3):  282-291.  doi:10.11947/j.AGCS.2015.20130423
    Asbtract ( )   HTML   PDF (3284KB) ( )  
    References | Related Articles | Metrics

    Laser scanning and image matching are both effective ways to get dense point cloud data, however, outliers obtained from both ways are still inevitable. A novel hierarchical outlier detection method is proposed for the automatic outlier detection of point cloud from image matching and airborne laser scanning. There are two main steps in this method. Firstly, the hierarchical density estimation is used to remove single and small cluster outliers. Then a progressive TIN method is used to find non-outliers removed in the previous steps. The experimental results indicate the effectiveness of this method in dealing with the two types of points cloud data. And this method can also handle low quality point cloud data from image matching. The quantitative analysis shows that the outlier detection rate is higher than 97%.

    An Automatic Cloud Detection Method for ZY-3 Satellite
    CHEN Zhenwei, ZHANG Guo, NING Jinsheng, TANG Xinming
    2015, 44(3):  292-300.  doi:10.11947/j.AGCS.2015.20130384
    Asbtract ( )   HTML   PDF (4284KB) ( )  
    References | Related Articles | Metrics

    Automatic cloud detection for optical satellite remote sensing images is a significant step in the production system of satellite products. For the browse images cataloged by ZY-3 satellite, the tree discriminate structure is adopted to carry out cloud detection. The image was divided into sub-images and their features were extracted to perform classification between clouds and grounds. However, due to the high complexity of clouds and surfaces and the low resolution of browse images, the traditional classification algorithms based on image features are of great limitations. In view of the problem, a prior enhancement processing to original sub-images before classification was put forward in this paper to widen the texture difference between clouds and surfaces. Afterwards, with the secondary moment and first difference of the images, the feature vectors were extended in multi-scale space, and then the cloud proportion in the image was estimated through comprehensive analysis. The presented cloud detection algorithm has already been applied to the ZY-3 application system project, and the practical experiment results indicate that this algorithm is capable of promoting the accuracy of cloud detection significantly.

    Method and Accuracy of Extracting Surface Deformation Field from SAR Image Coregistration
    CHEN Qiang, LUO Rong, YANG Yinghui, YONG Qi
    2015, 44(3):  301-308.  doi:10.11947/j.AGCS.2015.20130782
    Asbtract ( )   HTML   PDF (6604KB) ( )  
    References | Related Articles | Metrics
    InSAR can extract one-dimensional deformation along the line of sight of radar. SAR image coregistration and pixel offsets can be used to extract two-dimensional deformation along the azimuth and range directions, and can be considered as the significant complement for InSAR deformation measurement. Analyzing the method of extracting deformation field with the SAR image coregistration and pixel offsets, this paper presents the error model of deformation extraction along the azimuth and range directions. The main error components for deformation extraction from the pixel offsets are addressed. The experiments of coseismic deformation field extraction and error analysis are carried out with ASAR images of Bam earthquake and PALSAR images of Yushu earthquake. The results show that the coseismic deformation extraction accuracy is significantly affected by matching window size and oversampling factor. The deformation extraction error decreases with the increase of matching window size, and deformation extraction accuracy can be slightly improved with the increase of oversampling factor. Terrain effect can cause significant pixel displacements in SAR images over high-relief areas.
    Lake Storage Change Automatic Detection by Multi-source Remote Sensing without Underwater Terrain Data
    ZHU Changming, ZHANG Xin, LU Ming, LUO Jiancheng
    2015, 44(3):  309-315.  doi:10.11947/j.AGCS.2015.20130438
    Asbtract ( )   HTML   PDF (1551KB) ( )  
    References | Related Articles | Metrics
    Focusing on lake underwater terrain unknown and dynamic storage that is difficult to obtain by the traditional methods, a new method is proposed for lake dynamic storage estimation by multi-source and multi-temporal remote sensing without underwater terrain data. The details are as follows. Firstly, extraction dynamic lake boundary through steps by steps adaptive iteration water body detection algorithm from multi-temporal remote sensing imagery. And then, retrieve water level information from ICESat GLAS laser point data. Thirdly, comprehensive utilizing lake area and elevation data, the lake boundary is converted to contour of water by the water level is assigned to the lake boundary line, according to the time and water level information. Fourthly, through the contour line construction TIN (triangulated irregular network) model and Kriging interpolation, it is gotten that the simulated three-dimensional lake digital elevation model. Finally, on the basis of simulated DEM, it is calculated that the dynamic lake volume, lake area distribution and water level information. The Bosten lake is selected as a case studying to verify the algorithm. The area and dynamic water storage variations of Bosten lake are detected since 2000. The results show that, the maximum error is 2.21× 108 m3, the minimum error is 0.00002× 108 m3, the average error is 0.044×108 m3, the root mean square is 0.59 and the correlation coefficient reached 0.99.
    Moving Target Information Extraction Based on Single Satellite Image
    ZHAO Shihu, YIN Dan, DOU Xianhui, GUO Li
    2015, 44(3):  316-322.  doi:10.11947/j.AGCS.2015.20120720
    Asbtract ( )   HTML   PDF (1856KB) ( )  
    References | Related Articles | Metrics
    The spatial and time variant effects in high resolution satellite push broom imaging are analyzed. A spatial and time variant imaging model is established. A moving target information extraction method is proposed based on a single satellite remote sensing image. The experiment computes two airplanes' flying speed using ZY-3 multispectral image and proves the validity of spatial and time variant model and moving information extracting method.
    Personalized Map Symbol Design Mechanism Based on Linguistics
    LI Wei, CHEN Yufen, QIAN Lingtao, LIU Xiaohan
    2015, 44(3):  323-329.  doi:10.11947/j.AGCS.2015.20130758
    Asbtract ( )   HTML   PDF (2063KB) ( )  
    References | Related Articles | Metrics
    The personalization and intelligence of map service ultimately reflects in their symbol design. By establishing conceptual models of personalized map symbols, a theoretical discussion of the symbols is launched from a perspective which both human perceptions and logistic comprehension are considered in this paper, thus to help analyzing the relationship among geographic objects, map symbols and the interpretation of users and exploring the design basis of personalized map symbol. According to some key points such as relevant linguistic theories, the interpretation of the symbol contexts and symbolic statement syntax, design strategies of personalized map symbols is parsed. Thus, methods and processes of personalized map symbol design are proposed accordingly, following by experiments which could verify the hypothesis.
    Surface Area Computation with Regard to Nonlinear Terrain Factors
    XUE Shuqiang, DANG Yamin, BEI Jinzhong, LIU Jiping, DONG Chun, WU Bo, WANG Shijin
    2015, 44(3):  330-337.  doi:10.11947/j.AGCS.2015.20130816
    Asbtract ( )   HTML   PDF (992KB) ( )  
    References | Related Articles | Metrics
    Mitigating the differences of the surface areas computed by DEM data with different resolutions is meaningful in precisely doing area statistics and monitoring area changes. In this paper, we discuss the mathematical models to the surface area computation and give the influences to the computational accuracy. An area computation method of polygons on the landscape surface is proposed and this method has taken local terrain factors into account. Firstly, the least squares estimation of these local terrain factors is achieved by employing the Taylor series expansion of the spatial function, then these estimated terrain factors are applied to the DEM interpolation. Finally, the regular triangulated network is structured to approximate the theoretical area of the landscape surface. Experiments show that, in the mountainous area or hilly region where the nonlinear topographic signal is prominent, the computational area heavily relies on the space resolution of the DEM data and the impact to the surface area computation is very serious. However, due to the using of terrain factors estimated, the area computation strategy proposed can significantly improve the precision of the computed area from the low resolution DEM.
    RaPC:A Rasterization-based Polygon Clipping Algorithm and Its Error Analysis
    FAN Junfu, KONG Weihua, MA Ting, ZHOU Chenghu, JI Min, ZHOU Yuke
    2015, 44(3):  338-345.  doi:10.11947/j.AGCS.2015.20140017
    Asbtract ( )   HTML   PDF (1897KB) ( )  
    References | Related Articles | Metrics
    Computational efficiencies of traditional vector computing-based polygon clipping algorithms will decrease rapidly when handling polygons contain large amount of vertices. The computing flows of traditional polygon clipping algorithms are tightly coupled with special data structures, which difficult to be optimized in the underlying of them. Under the premise of meeting a certain degree of area errors, the polygon clipping problem can be solved by introducing the idea of rasterization processing. In this research, we proposed a new rasterization processing-based polygon clipping algorithm: the RaPC algorithm, on the basis of analyzing the characteristics of existing algorithms. The area errors of results of the new algorithm are also analyzed and discussed. Experimental results show that the efficiencies of the RaPC algorithm can be enhanced significantly when using large grid cells, and it shows a linear trend growth with the increase of amount of polygon vertices. Compared with the Vatti algorithm, the RaPC algorithm represents more efficiencies on dealing clipping issues between polygons with large amount of vertices, the former shows lower time costs when handling polygons with less vertices. The area error of computing results of the RaPC algorithm is closely related with the grid size, and errors can be reduced using smaller grid sizes. Therefore the RaPC algorithm showed higher efficiencies on processing polygons with large amount of vertices than the Vatti algorithm and presented practical values to some degree.
    Polygon Growing Algorithm for Network Schematic Maps
    ZHANG Lan, LI Jiatian, XU Heng, HE Feiyue, XU Yanzhu, WANG Hongmei
    2015, 44(3):  346-352.  doi:10.11947/j.AGCS.2015.20130724
    Asbtract ( )   HTML   PDF (1336KB) ( )  
    References | Related Articles | Metrics

    Network schematic map is the abstract representation of entity network. It has been applied in the field of map service and cartography because it is more consistent with people's cognitive habits. The previous route-based auto schematic algorithms have only considered the local arrangement of nodes and are difficult to maintain topological consistency. In reaction to the deficiency, a new polygon-based algorithm is proposed in this paper, which uses the closed polygons (mesh) as the basic unit of the network for their independence and adjacency. The network is regarded as closed polygons and non-closed line segments. The main progress is extracting, mapping and combining closed polygons. Experimental analysis shows that this algorithm is more effective in balancing network spatial distribution and maintaining topological consistency.

    Ionospheric Disturbance Analysis and Delay Correction Algorithms for Landslide and Earthquake Monitoring
    HE Liming
    2015, 44(3):  353-353.  doi:10.11947/j.AGCS.2015.20140561
    Asbtract ( )   HTML   PDF (708KB) ( )  
    Related Articles | Metrics
    Study on the Key Matching Algorithms for Oblique Stereo Images and Its Application
    YAO Guobiao
    2015, 44(3):  354-354.  doi:10.11947/j.AGCS.2015.20140548
    Asbtract ( )   HTML   PDF (705KB) ( )  
    Related Articles | Metrics