Discrete Global Grid Systems(DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. They provide an organizational structure that permits fast integratio...Discrete Global Grid Systems(DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. They provide an organizational structure that permits fast integration between multiple sources of large and variable geospatial data sufficient for visualization and analysis. Despite a significant body of research supporting hexagonal DGGSs as the superior choice, the application thereof has been hindered owing in part to the lack of a rational hierarchy with an efficient addressing system. This paper presents an algebraic model of encoding scheme for the Aperture 3 Hexagonal(A3H) DGGS. Firstly, the definition of a grid cell, which is composed of vertices, edges, and a center, is introduced to describe fundamental elements of grids. Secondly, by identifying the grid cell with its center, this paper proves that cell centers at different levels can be represented exactly using a mixed positional number system in the complex plane through the recursive geometric relationship between two successive levels, which reveals that grid cells are essentially special complex radix numbers. Thirdly, it is shown that through the recursive geometric relationship of successive odd or even levels, the mixed positional number system can also be applied to uniquely represent cell centers at different levels under specific constraint conditions, according to which the encoding scheme is designed. Finally, it is shown that by extending the scheme to 20 triangular faces of the regular icosahedron,multi-resolution grids on closed surfaces of the icosahedron are addressed perfectly. Contrast experiments show that the proposed encoding scheme has the advantages of theoretical rigor and high programming efficiency and that the efficiency of cross-face adjacent cell searching is 242.9 times that of a similar scheme. Moreover, the proposed complex radix number representation is an ideal formalized description tool for grid systems. The research ideas introduced herein can be used to create a universal theoretical framework for DGGSs.展开更多
全球离散格网系统(Discrete Global Grid System,DGGS)是数字化的地球参考框架,在多源、多尺度地球空间数据集成分析方面优势明显。本文选择菱形三十面体六边形全球离散格网系统,提高格网与地球的整体拟合精度和空间采样率;建立遥感图...全球离散格网系统(Discrete Global Grid System,DGGS)是数字化的地球参考框架,在多源、多尺度地球空间数据集成分析方面优势明显。本文选择菱形三十面体六边形全球离散格网系统,提高格网与地球的整体拟合精度和空间采样率;建立遥感图像六边形像素数学模型,提出兼容开放标准格式的数据存储方案。①根据地理位置将遥感图像格网化,完成遥感图像六边形DGGS建模;其次,建立六边形单元与矩形像素严密对应关系,等效保留六边形单元的邻域信息;②采用GeoTIFF开放标准格式精确存储六边形属性值以及投影、变换参数;③设计依托六边形DGGS格网标准数据集为基础的多尺度六边形DGGS生成算法。实验结果表明:本文方案不仅能保证六边形像素遥感图像数据与标准文件格式兼容,而且能保证矩形像素与六边形单元逐一对应,较好地保留了六边形单元数据的图像信息和空间分布特征,相较于欧空局SMOS数据组织方案更具优势。本文方案打破了六边形单元与矩形像素遥感图像的数据组织壁垒,使用常见GIS/RS软件即可读取六边形像素的遥感图像,并可通过对矩形像素的操作等效实现对六边形单元的处理,有望推动六边形DGGS在遥感数据组织、处理、共享等方面的应用。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41671410)the Postdoctoral Science Foundation of China (Grant No. 2013T60161)the Excellent Young Scholar Foundation of Information Engineering University (Grant No. 2016610802)
文摘Discrete Global Grid Systems(DGGSs) are spatial references that use a hierarchical tessellation of cells to partition and address the entire globe. They provide an organizational structure that permits fast integration between multiple sources of large and variable geospatial data sufficient for visualization and analysis. Despite a significant body of research supporting hexagonal DGGSs as the superior choice, the application thereof has been hindered owing in part to the lack of a rational hierarchy with an efficient addressing system. This paper presents an algebraic model of encoding scheme for the Aperture 3 Hexagonal(A3H) DGGS. Firstly, the definition of a grid cell, which is composed of vertices, edges, and a center, is introduced to describe fundamental elements of grids. Secondly, by identifying the grid cell with its center, this paper proves that cell centers at different levels can be represented exactly using a mixed positional number system in the complex plane through the recursive geometric relationship between two successive levels, which reveals that grid cells are essentially special complex radix numbers. Thirdly, it is shown that through the recursive geometric relationship of successive odd or even levels, the mixed positional number system can also be applied to uniquely represent cell centers at different levels under specific constraint conditions, according to which the encoding scheme is designed. Finally, it is shown that by extending the scheme to 20 triangular faces of the regular icosahedron,multi-resolution grids on closed surfaces of the icosahedron are addressed perfectly. Contrast experiments show that the proposed encoding scheme has the advantages of theoretical rigor and high programming efficiency and that the efficiency of cross-face adjacent cell searching is 242.9 times that of a similar scheme. Moreover, the proposed complex radix number representation is an ideal formalized description tool for grid systems. The research ideas introduced herein can be used to create a universal theoretical framework for DGGSs.
文摘全球离散格网系统(Discrete Global Grid System,DGGS)是数字化的地球参考框架,在多源、多尺度地球空间数据集成分析方面优势明显。本文选择菱形三十面体六边形全球离散格网系统,提高格网与地球的整体拟合精度和空间采样率;建立遥感图像六边形像素数学模型,提出兼容开放标准格式的数据存储方案。①根据地理位置将遥感图像格网化,完成遥感图像六边形DGGS建模;其次,建立六边形单元与矩形像素严密对应关系,等效保留六边形单元的邻域信息;②采用GeoTIFF开放标准格式精确存储六边形属性值以及投影、变换参数;③设计依托六边形DGGS格网标准数据集为基础的多尺度六边形DGGS生成算法。实验结果表明:本文方案不仅能保证六边形像素遥感图像数据与标准文件格式兼容,而且能保证矩形像素与六边形单元逐一对应,较好地保留了六边形单元数据的图像信息和空间分布特征,相较于欧空局SMOS数据组织方案更具优势。本文方案打破了六边形单元与矩形像素遥感图像的数据组织壁垒,使用常见GIS/RS软件即可读取六边形像素的遥感图像,并可通过对矩形像素的操作等效实现对六边形单元的处理,有望推动六边形DGGS在遥感数据组织、处理、共享等方面的应用。
