Study And Application In Visualization Of Radar Image Based On VTK

With the improvement of living standards and development of economic construction, more and more serious damages are caused by the severe convective weather. Doppler radar is an effective tool to detect severe convective storm. Since the sixties of last century, its detection result has been providing an important basis for the research of strong storm system structure and evolution. Through using the Doppler weather radar to instantly monitor the strong convective weather, we can access its three-dimensional internal structure. Using the three-dimensional visualization techniques to analyze the internal structure of convective weather is one basic technique to warn the strong convective weather, also it is applied widely in the business sector.In recent years, China has preliminarily established the three-dimensional Doppler weather radar network. At the present stage, functions of the domestic radar data visualization system are limited and its display program is complicated. If the three-dimensional model can be used to express the three-dimensional radar data volume, wealth information of the clouds in different regions would be more intuitively showed. Scientific computer visualization converts the data which is calculated by scientific or collected to image by using computer graphics technique and image processing technology. VTK is an open source and excellent visualization toolkit, it can be used to develop highly efficient and stable three-dimensional visualization system rapidly.According to the necessary of the radar image's display, this paper adopts NVI(Neighbor and Vertical Integration) method to convert radar data from Polar coordinates to Cartesian coordinates, then preprocesses the data just like filtering to reduce the noise. When the data processed is fused with VTK, it will generate new data and the fused data will be processed as the basic data to make the visualization technology come true.The visualization technology used in this paper contains surface rendering and volume rendering. MC algorithm is used to extract the equivalence surface in surface rendering technology and ray-casting algorithm is used in volume rendering technology. After setting color,lighting effects,resampling and synthesizing the image can be displayed. This paper mainly used the RayCastCompositeFunction to render the volume.The experimental results indicate that radar image can be quickly displayed through setting different parameters under the RayCastCompositeFunction. By using VTK, three-dimensional image is quickly reconstructed from the two-dimensional radar image sequence; arbitrarily three-dimensional sections of the radar echo intensity on the X,Y,Z coordinate are showed; any direction can be clipped to make the interesting section be observed. In addition, it achieves other advanced functions like rotating,zooming,panning the image and interacting the two-dimensional image with the three-dimensional image.When VTK is used in the three-dimensional visualization of radar image, the spatial distribution of the echo can be more intuitively and fully displayed to make up the lack of radar display through the comprehensive explanation of the three-dimensional space, which can give full play to the display of the meteorological service system; also it can provide more help to develop the warning system of storm by using the echo material.