Ray tracing with the improved shortest path method

Abstract

The shortest path ray tracing is a kind of efficient and flexible method to calculate global minimum traveltimes and raypaths. However, the derived zigzag raypaths can generate errors in both traveltimes and loci. Increasing the number of nodes and propagation directions from a secondary source can improve the situation. But it also increases much computation. Here, several measures are presented to improve the efficiency and accuracy of the shortest path method (SPM). First, Snell's law is considered when searching wave propagation directions from a secondary source. Thus, a large number of unnecessary directions are discarded. Second, when tracing reflections, a measure is applied to keep from tracing areas below interfaces. Third, traveltimes and raypath loci are corrected with a nonlinear interpolation scheme. In addition, a special SPM, named interface point method, is presented. It can tracing blocky models with high efficiency and accuracy.