Key Technology Research Of Infinite Scale On Digital Ocean

"Digital Earth" is the 3D expression of Earth multi-resolution, it allow us get geographic information in different details from different viewpoints. In order to resolve the contradiction between infinite spatial geographic information and limited data display window, we need infinite scale technology.The realization of infinite scale mainly depend on spatial database, so the building approach of infinite scale based spatial database is referred in this paper. This approach include the establishment of database model, the definition of data structure, the study of database function, the data sharing method and the release of spatial information. Spatial data model determines which kind of data can be included in spatial database, and which kinds of service are provided. Data storage and management, and the external user how to access data are all depend on the functions provided by database, so spatial database functions is the key part of the spatial database. Spatial data sharing is one of the most important parts of digital earth, and database can take the full advantage of existing data only after having well data sharing mechanism. Spatial data release is the interface which can provide useful data to user, without release, data will have no use.Spatial data model and spatial data structure basically determine the functions of spatial database. To patch the deficiency of vector data and raster data, the data model in our spatial database integrates these two kinds of data. Hypergraph does not only provide the object oriented hierarchy, but also provide the relations among layers. This feature makes it meet the inheritance and relevance of geographic spatial data. S-57 international standard is the electronic chart data transfer standard of International Hydrographic Organization (IHO) and International Maritime Organization (IMO). This standard provides the theoretical model, definition of data structure and concrete definition of objects. This paper adopts S-57 data model and hypergraph data structure to establish an infinite scale oriented spatial data model.Map generalization is the precondition of infinite scale. It includes graph deformation, the judgment of generalization time and the deformation after generalization. To resolve these problems, this paper adopts rough set. We consider raster grid in different scales as equivalence partitioning, and using algorithm of up/down approximation and boundary to study the topological deformation, and bring forward the topological deformation algorithm. Then using aggregation interest to judgegeneralization moment, and bring forward the concept of neighborhood, to make the judgment of generalization moment more flexible. It reduces complexity of traditional algorithm and improves the compute efficiency. According the down approximation algorithm, I bring forward the deformation algorithm after topological graph generalization.Information generalization was treated as the extension of map generalization. With the change of graph, the attributes in these graphs are changed at the same time. This paper mainly discusses the information generalization. In information generalization, we establish a spatial layer database, to judge the sub-objects of spatial objects, and generalize the attributes of sub-objects into parent objects. Each object is a data object, and all kinds of spatial objects generalization functions were established in original spatial database. When scale exceeds the relevant threshold value, it triggers the relevant generalization function. After generalization, it searches in spatial layer database, generalize parent object's attribute.Spatial data sharing and interchange is another important research aspect of infinite scale database. Firstly, we establish a Meta data oriented management system, and bring forward infinite scale oriented spatial Meta data catalog. The Meta data can describe spatial data and finish the spatial data sharing. According to study the four level of spatial information sharing, we bring forward sharing approach for each level. They are TCP/IP in network level, XML transfer standard in data level, OGC semantic criterion in application level and spatial information frame in enterprise level. All these are based on Internet technology.Spatial information release adopts multi-platform architecture, and using JAVA program browser plug in unit. It defines the concept model and external model of database, defines message transferred between browser and server, and finish the functions in browser, such as zoom, pan, query. In order using the compute ability of workstation, the system equalizes all functions in server and browser.