Two methods to map crack edges by the use of arrival times of edge-diffracted signals have been briefly reviewed. They are a global triangulation method and a local crack-edge mapping technique. The local mapping technique, which generally has the greater accuracy, has been applied to both synthetic and experimental data. The effect of a uniform error in the data has been investigated. The experimental data were obtained at the Rockwell International Science Center for a doorknob specimen with a plane crack of elliptical shape at its center. Crack mappings of very satisfactory accuracy were achieved.