Research On Discrete Global Grid System Considering Geospatial Interaction

In order to effectively control the further deterioration of human's survival environment and reduce the loss caused by environmental changes,Earth System Model must be utilized to inverse the evolution mechanism of resources and environment in the past and predict the future global change scenes based on the information of huge amounts of natural and human's activities.However,the differences in the fundamental data structure and encoding model,leading to an imperfect expression of geographical spatial interaction from Discrete Global Grid System in the field of surveying and mapping,make Discrete Global Grid System so difficult to support the calculation of Earth System Model directly.Therefore,it is the major task of Geography,Earth Sciences or related disciplines to adopt a unified spatial data framework to organize and manage various massive spatial data with different resolutions,and couple with Earth System Model covering the whole world.This paper inherits global coverage,homogeneity and hierarchical nesting structure based on the geometry fundamental framework of the existing Discrete Global Grid System,and expands its expression of a single cell to a unified grid-point and grid-edge system through extending its elment coding structure and is eventually used as a basical grid system for comprehensive expression of different kinds of geographical phenomenon,objects and evolution process,which provides the effective support for the multi-level expression of spatial data and calculations of Earth System Sciences.This paper mainly contains the followong research contents and achievements:(1)From perspective of three grid elements,spherical triangular grid on icosahedron in this paper is compared with grid on octahedron or icosahedron.The results show that this kind of grid can effectively support global spatial data's modeling and numerical model's calculation for stable and approximate uniform geometrical properties on different levels.(2)The space filling curve is introduced into the existing icosahedron spherical triangular grid and one-to-one relationship is subsequently constructed between all kinds of grid's elements and grid code following the principle of subordination relation.Then the unified-element coding model with explicit expression of grid-node,grid-edge and grid-cell is built and realizes the unification of the underlying structure of multi-scale spatial data from Dicrete Global Grid System and Earth System Model.Based on the unified-elements encoding scheme the fast conversion method between the geographic coordinates and grid code is implemented,and searching methods in spherical space,such as space adjacent relationship and hierarchical relationship,are also realized.(3)Faced with the differences between expression paradigm of the widely used field and vector data,transformation from the existing geospatial data to the grid format is realized by conversion methods between grid element's coordination and code,and rapidly visualization of discrete objects and continuous fields data in the spherical grid space alse comes true with mature computer graphics algorithm as reference,which contributes to reaching the goal of both multi-resolution spatial data expression and Earth System Model calculation.(4)With unified-element coding structure for spherical triangular grid system and global ocean numerical models taken into consideration,preliminary formation of global ocean grid is accomplished firstly by means of topological relations judgment and area weight.Local grid in coast border area is refined by using the global hierarchical nesting characteristics of Dicrete Global Grid System.According to the requirement of the ocean numerical model for boundary smoothness,boundary special treatment is taken to remove undesirable triangular cells.Based on the ultimate grid geometric framework,gird-node begin to gain and optimize its attribute,and lead Dicrete Global Grid System to directly support ocean numerical model to run smoothly.The results show that spherical triangular grid system on icosahedron in this paper can meet the dual requirement of spatial data expression and Earth System Model's calculation under the premise of geographical spatial interaction,which overcomes the shrtcomings and limitations of current Dicrete Global Grid System and numerical calculation mesh,and constucts a complete Earth System Model running environment,composed of data organization,spatial analysis,model simulation and results visualization ability,to provide strong support for the Earth System's mechanism in the process of inversion and prediction.