An efficient algorithm of the network shortest path calculation of rays and travel times of the first arrivals is described. The travel-time error of such computations is estimated. The rough estimate of the relative travel-time error is evaluated locally at all network nodes prior to network ray tracing, and is minimized by means of a proper choice of the sizes of forward stars. In this way, the structure of the network is adjusted for a particular model and for a particular computer memory. After network ray tracing, the error estimate is refined and the absolute error bounds of the calculated travel times are evaluated. The method and its accuracy is demonstrated on numerical examples.
Graph, network, shortest path, travel time, two-point ray tracing.
The image of the reprint in GIF 150dpi (4856 kB !) is designed for an instant screen preview.
The scanned image of the reprint in PDF 300dpi (1215 kB !) is designed for printing.
The manuscript of the paper is available in GZIPped PostScript (666 kB, unGZIPped PostScript has 37358 kB). Quality of Figure 5 is much better in the manuscript than in the image of the reprint.