The Research Of Spatio-temporal Feature Analysis And Visualization On Marine Flow Field Based On Topological Theory

Flow field visualization is one of the important components ofvector field visualization. The flow field has the typical topological characteristics generally, which is especially important for exploring the law of flow field. Through topological features extraction and analysis and visualization of the flow field, we can deeply understand and summarize the temporal and spatial variation of the oceanic flow field,so as to enrich the research on the theory and method of marine spatio-temporal data model, and also provide effective spatial information visualization tool for the technical needs of the digital ocean,and provides a concise and clear way for researchers to understand the flow field.In this paper, the large-scale ocean flow field is taken as the research object, the scalar and vector data of the oceanic flow field are extracted on the basis of the pretreatment of the oceanic flow field data in the NetCDF format. Two kinds of ocean flow visualization methods,streamline mapping and texture mapping method, are investigated and used in visualization of flow field.In the visualization of flow field based on streamlined construction algorithm, the topology analysis method is used to extract critical points and analysis topological structure of the flow field. The calculation model of adaptive-step based on the change of flow direction and the speed of flow field are used to calculate the step, particle points are tracked in two directions. The problems existing in the process of streamline generation are' analyzed and the model is improved.Visualization technology is used to display the geometric data obtained from the mapping process in World Wind, and the results of the algorithm before and after the improvement of the model are compared,The results show that the improved algorithm is feasible and the applicability is wider, which can improve the efficiency of visualization of flow field, reduce the data storage capacity and improve the expression.In the visualization of flow field based on texture mapping algorithm, the LIC line integral convolution method is used to convolve the local streamlines, In the algorithm, the local streamline length of each grid is calculated according to the velocity of flow. According to the problem that the obtained texture can only reflect the flow direction information of the flow field, the algorithm is improved. The grid pixel value is obtained according to the flow velocity, and the result and LIC texture are fused by weighting to obtain color texture. It is proved to be feasible and effective by rendering the results of rendering algorithm in World Wind. It has practical significance.