| Discrete Global Grid Systems(DGGSs)break through the limitation that arise from the representation of flat information,and use a specific method to recursively subdivide the curved earth surface to form seamless multi-resolution grids,which have uniform shape and nested with each other.DGGS provides a reliable theoretical basis for the description of complex and diverse geographical phenomena and widely used in the fields of spatial data expression and earth system model,DGGS in the two fields are similar in geometry,however,there are significant differences in their components.Different DGGSs have their own characteristics,they are not transformed with each other,it is difficult to carry out effective data integration or system coupling.Therefore,the universal description of multiple grids based on data expression and model calculation can improve the ability of DGGS data sharing,analysis and visualization,and promote the development of DGGS applications.Based on the existing DGGS research results and core characteristics of DGGS,this paper uses the fiber bundle theory to express a variety of DGGS data and designs a universal data model of DGGS.The implicit expression of semi-regular grid is also realized through regular arrangement.Finally,the prototype system is formed by designing grid data organization,service and visualization methods for verifying the support of the data model of multiple grids.The contents and achievements of this paper mainly include:(1)Taking the semi-regular grid as an example,the components of DGGS are summarized,including Platonic solids,subdivision method,projection method and grid coding.This paper also summarizes the relationships contained in DGGS,including temporal relation,hierarchical relation,adjacent relation and relation among components.The conceptual model is constructed from the components and relationships of DGGS.(2)Based on the fiber bundle theory in integration of time and space,this paper designs an acyclic graph to express multiple grids,and realizes regular arrangement of semi-regular grid by using internal relation of three semi-regular grids,including triangle,diamond and hexagon.The regular arrangement storage method of semi-regular grid efficiently express multiple grids relationships.At same time,a universal data model of DGGS is formed.(3)According to the nested features of grids,a diamond block structure is designed,grids are divided by diamond block and each diamond block is indexed by space filling curve,then the grid pyramid model is realized.As a result,an efficient grid data integration method based on the diamond block structure is proposed in this paper.Finally,an organization and service of the grid diamond block structure is realized by the document-oriented database and service technology.The experimental results indicate that the universal data model of DGGS proposed in this paper based on the fiber bundle can descript multiple grids,which overcomes the shortcoming that multiple grids are independent of each other and descripts the temporal relation and the relation among components.It is an important supplement to the existing grid data models.The implicit expression of semi-regular grid proposed in this paper is more efficient,and overcomes the shortcomings of storage structure.The grid data organization and service method based on diamond block has higher concurrency efficiency,and also provides new ideas for the development of DGGS applications. |
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