Abstract：Using the Format's principle,the paper presented a fast and effective ray tracing method-ray tracing with minimum time.First,using cubic spline function to describe the geologic model in detail,then using format's principle to introduce deferential form for a set of raypath equations.In order to make sure of robustness and accuracy of the algorithm and that the raypath can be successfully obtained,the paper suggested that in a condition of tolerable operation speed,we can do our best to use multiple solving methods simultaneously and present multigroup different initial values to solve the problem of multiple roots,then,briefly introduced solving process by taking gradient method as an example and deduced main numeric calculation formula of gradient method.The results of model test show that the method presented 6y the paper has character of accuracy and is suitable for complex geologic model,its calculating speed raised two orders as compared with target method.
