Research Of Implementation Technique Of Cesium-based WebGIS 3D Client

In recent years, with the development of geographic information technology, GIS systems are widely used in various fields. However, GIS system is still facing a lot of problems.At present, most GIS systems of manufacturers to handle two-dimensional data model is still dominated, it has significant limitations in the display and analysis of geospatial information, it is difficult to meet the application needs of people for city planning and management, modeling of subsurface geology, mining and oil development in areas such as. In addition, GIS systems based on C/S architecture need to provide the GIS client of appropriate version for different operating system respectively, which increases the difficulty of developing and managing GIS client in a certain extent. Therefore, the research and development of cross-platform 3D GIS client has an important significance.This paper proposes a solution against the above problems existing in GIS system, which is Cesium-based Web GIS 3D Client. Cesium is an open source Java Script library that implements a functionality of displaying three-dimensional virtual globe in browser. At the same time, Cesium uses B/S architecture and follows the Web GL 3D graphics standard,with the advantages of two or three dimensional integration, cross-platform, computing with high precision. In this paper, the research work done and innovations about Cesium include the following aspects.1.The functionalities of the open source library Cesium have been analysed and studied,such as image layers, elevation layers, geometric elements and so on. And they were flexible used in the project.2.Through the analysis of Cesium library source code, the visualization technology of map terrain in 3D scene has been studied and summarized. The implementation of scheduling algorithm related to tile in the process has been cleared.3.Through the analysis of Cesium library source code, the visualization technology of vector elements in 3D scene has been studied and summarized. The core processes of the visualization of static vector elements and dynamic vector elements have been cleared.The principle of vector elements changing with time has been cleared as well.4.Modules related to GIS have been designed and implemented on the basis of the study of Cesium visualization technologies, such as layer tree and management module, geo-graphic grid module, box query module, feature bubbling module and interactive feature labeling module. And these modules have been tested.Cesium-based three-dimensional client proposed in this paper not only combines the advantages of Web GIS cross-platform, development with high efficiency, easy expansion,but also combines the advantages of three-dimensional client displaying spatial information intuitively and analysing spatial information powerfully. After testing, Cesium modules designed and implemented in this paper is reliable and manageable, achieving the desired effect. The functionalities of the modules implemented have an important significance for browsing, querying, locating, contrasting and managing GIS data.