Research And Design Of Web Three-dimensional Thematic Map Visualization Framework

With the continuous development of Geographic Information Technology,threedimensional thematic maps have been widely used in various fields in recent years to help decision makers understand and analyze various phenomena with spatial characteristics,such as population distribution maps,forest coverage maps and so on.Web threedimensional thematic maps are thematic maps visualized in Web GIS three-dimensional clients,which have the advantages of displaying information intuitively,displaying data features clearly,processing data deeply and supporting user interaction,etc.The realization of Web three-dimensional thematic map involves many complex problems,such as virtual globe display,visualization of geographic basemap,visualization of thematic content,etc.Although many companies and open-source organizations have developed a series of Web map visualization frameworks,there are few specific frameworks for achieving visualization services of three-dimensional thematic maps.Existing frameworks only solve parts of these problems and lack direct support for the visualization of three-dimensional thematic maps.In view of the above problems,this thesis puts forward the concept of Spatial Data Representation Model and Visualization Model based on the full study of existing Web map visualization frameworks.We designs and implements a new three-dimensional thematic map visualization framework which includes Spatial Data Representation Model,Visualization Model,and UI framework based on the open-source three-dimensional library Cesium.This framework supports the use of HTML5's graphics rendering mechanism in browsers to visualize three-dimensional thematic maps.The main work of the thesis is as follows:(1)Study the overall structure of existing frameworks,and design the overall structure of the framework studied in this theis with logical,hierarchical structures.(2)Study the Spatial Data Representation Model of existing frameworks,design and implement the Spatial Data Representation Model of the framework.This module includes the functions of visual display of virtual globes and the visualization of geographical basemaps which solves the problems of confusion of Spatial Data Representation Model modules and inconsistency of general concepts in Cesium.Beyond the realization,this thesis adds the Spatial Reference System module to support access to Web Mercator projection coordinate system type data.(3)Study the Visual Model of existing frameworks,design and implement Visual Model in this framework.This module includes the function of thematic content visualization,and solves the problems of confusion in spatial position representation and lack of symbolism system in Cesium.(4)Analyze the current situation of UI frameworks,study the UI frameworks of existing frameworks,design and implement the UI framework for this thesis.The module enhances the visualization of thematic content,and solves problems of the single style style in the existing UI framework,the incomplete separation of logic and style,the lack of legend components and the difficulty of using popup components.Aiming at Web three-dimensional thematic map visualization framework designed and implemented in this thesis,the author builds a B/S mode test system.The system server uses Node.js technology and the Express framework to provide services.The client is based on the framework of this thesis.By writing test cases to access multiple sets of thematic data,three modules of the Spatial Data Representation Model,the Visual Model,and the UI framework are functionally tested.The test results show that the Web three-dimensional thematic map visualization framework designed and implemented in this thesis has the advantages of good encapsulation,ease of use,and rich functions.It achieves the expected design goals and meets the application requirements of actual scientific research projects.