Research On Web Visualization Of Spatio-Temporal Trajectory Data

With the rapid development of mobile internet which based on mobile intelligent terminal equipment, so that people can collect and storage a variety of spatio-temporal trajectory data of the moving objects timely, at the same time there are a lot of spatio-temporal trajectory data of the moving objects are recorded imperceptibly, eventually a vast amount historical trajectory data are accumulated. The position changes and activity patterns of the people and vehicles in urban space are recorded by spatio-temporal trajectory, the visualization of spatio-temporal trajectory data for large-scale moving objects can help us to observe the rules and characteristics hidden behind the spatio-temporal trajectory data intuitively, thus helping users to effectively analyze the mobile distribution relevant of population, the city’s traffic conditions, the characteristics social activities and the dynamics of cities. In addition, with the enhancement of the browser and the improvement of HTML5 technology, it is possible to achieve free plug-in visualization of spatio-temporal trajectory data on browser, to realize the free plug-in visualization and real-time publish of spatio-temporal trajectory data under the network environment has become a important research direction. Recent study of free plug-in web visualization of spatio-temporal trajectory data based on HTML5 is still less, so it has important theoretical and practical value to study the web visualization and real-time publish of spatio-temporal trajectory data, and extract spatial and temporal characteristics from the visualization result.This paper focuses on web visualization techniques of spatio-temporal trajectory data, with researching of the key technology of HTML5, we have realized the dynamic visualization method of spatial and temporal data for groups based on particle tracking technology and the space-time path visualization method based on WebGL technology. The proposed methods can simulate continuous changing process of traffic, crowd and other moving objects in urban space time under the support of real spatio-temporal trajectory data. The principal contents and achievement of this paper are summarized as follows:(1) The design and implementation of spatial-temporal trajectory data visualization framework based on HTML5Through the study of database, the browser and the Web server-related content, using WebSocket to realize the data transmission between browser and server, and using HTML5 graphics rendering methods to realize graphics rendering in browser, the architecture system of spatial-temporal trajectory data web visualization based on HTML5 is designed, it provides a solutions of free plug-in visualization publish of large-scale spatio-temporal trajectory data. The proposed framework is developed by Model, View and Controller, the whole visual process is divided into three portions, including visual data layer, the service layer, and the performance, finally achieving a low coupling between the different layers, and easy to expand to a different application purposes.(2) The research of spatio-temporal trajectory data processing algorithmsStudying invalid data cleaning algorithms of the space-time trajectory data, a interpolation algorithm based on Cat-mull curve, a conversion method between map coordinates and Canvas coordinates, finally, we implement the data preprocessing.(3) The dynamic visualization method of groups spatio-temporal trajectory data based on particle tracking technologyUsing HTML5 Canvas, WebSocket, and particle system to achieve a layered rendering of vector data, the fast real-time transmission of spatio-temporal trajectory data and visualization simulation, and the method has the characteristics of cross-platform, free plug-in, easy maintenance.(4) The space-time path visualization method based on WebGL technologyUsing WebGL technology to achieve three-dimensional space-time path web visualization, and realizing a three-dimensional space-time interactive visualization path, including zoom, roaming, angle adjustment, the space-time path visualization method can analyze spatio-temporal trajectory of individuals or crowds from a long time scales. The method provides an effective and image representation to analyze and display the characteristics of moving objects in continuous space-time environment, it is an important means of spatio-temporal trajectory data visual expression.(5) Practice on web visualization method of spatio-temporal trajectory dataBased on the study of web visualization space-time trajectory method, we design and implement the Qingdao city bus visualization systemIn this paper, we design and implement the Qingdao city bus visualization system and the space-time path visualization case study based on travel information collection method based on mobile phone to verify the feasibility and practicality of the proposed method.In this paper, we achieved the free plug-in visualization and real-time publish of spatio-temporal trajectory data on the web browser, it provides a new technical approach and idea for spatial and temporal trajectory data two-dimensional dynamic and three-dimensional space time path free plug-in visual simulation under the network environment. Practice has proved that the proposed the Web visualization methods of spatio-temporal trajectory data can realize dynamic visualization and simulation temporal process, and the method has the characteristics of cross-platform, free plug-in, fast response and easy maintenance.