| With the development of economy and society and modernization level, more and more serious hazards and heavy economic losses are arising from lightning disturbance and influence society greatly. Lightning disaster frequently occurs in Hunan province, and the society gives more and more attention to Lightning Protection and Disaster Reduction. There are multiple techniques for observation and analysis of lightning disaster at present, the concerning data from which has many characteristics such as large scale, various types and complex structure. However, there are some shortcomings in the visualization technology of lightning disaster data in Hunan, such as low rendering speed, limited real-time interactive ability, etc. So, it is necessary to explore an effective visual system of processing and analyzing lightning disaster data for Lightning Protection Department in Hunan.Based on systemic research on visual algorithms, techniques and software tools, according to some problems related with lightning disaster data processing and analysis, combination with characteristics of thunderstorm day data, lightning disaster survey data, Lightning-Direction-Finder data and Doppler Radar data, rapid rendering method for Doppler Radar Figure based on User Draw Layer, drawing strategies for lighting density figure and polarity figure based on database, management technology for multimedia data based on Memory-Stream, and rapid merging display technology for Doppler Radar data and Lightning-Direction-Finder data are analyzed specially, some correlated methods have been finished, and visual analysis system for lighting disaster data named with VASLDD was achieved, moreover lots of typical application on lighting disaster examples were listed in this paper. The main research results are as follows.(1) The rapid rendering method for Doppler Radar Figure based on User Draw Layer is put forward, which adopts the User Draw Layer technology to accelerate rendering speed. Based on the study of Doppler radar product data structure and large data from Doppler radar, comparing with drawing speed using the general drawing Object-Oriented method, results showed that the speed of the rapid rendering method with user draw layer has increased by three times than the general drawing method.(2) The drawing strategy of lighting density figure and polarity figure based on database is presented in this paper. By deeply analyzed the recent drawing theory of lighting density figure and polarity figure, the bottleneck about the low drawing speed caused by low accessing efficiency was found. the classified search strategy based on database is adopted to improve the efficiency of data access. Experiment results showed that the speed was increased by 2-3 times.(3) Based on The management technology of multimedia data of Memory-Stream was advanced here. Because Memory-Stream was taken as medium to avoid write and read on disk, the access efficiency of multimedia data was improved.(4) Rapid merging display technology of Doppler Radar data and Lightning Direction Finder data was realized, visual technology of lightning disaster survey based on GIS, the isoline / choroplethic map drawing technology based on GIS and ActiveX automation. These technical realizations enrich Visualization approaches of lighting disaster data.(5) The visual analysis system for lighting disaster data, named VASLDD, was established in the study. this system is based on C/S mode, and supporting many kinds of techniques such as diagram, thematic map , choroplethic map, etc for analyzing lightning disaster data. VASLDD has many advantages such as powerful, strong interaction, good real-time and friendly interface. Moreover, VASLDD has been put into operation by Hunan Lightning Protection Department and promoted development of lightning protection and disaster reduction. There is no report on same kind system in domestic meteorology industry. |
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