Opportunities for the Use of Electronic Distance Measurement Instruments in Nondestructive Testing and Structural Health Monitoring Applications and How Instrument Manufacturers Can Facilitate Early Adopters in New Fields

Abstract

Electronic distance measurement (EDM) instruments, such as laser trackers, total stations, and handheld laser distance meters have been used in a limited number of nondestructive testing (NDT) and structural health monitoring (SHM) applications attempting to measure bridge deflections and vibrations. However, a survey of the literature reveals that by far, most attempts have been by measuring elevation angles with robotic total stations. One case was found that used a Leica AT401 laser tracker, but it also measured deflections by measuring the elevation angle, i.e., like the total station cases, the measurement architecture did not exploit the higher accuracy and speed of EDM. One case was found using a non-commercial laser ranging instrument, similar to handheld laser distance meters, that did measure vertical deflections of a bridge, from the instrument fixed on the ground to a point directly above the instrument, at 200 measurements/second, with good results. Only one case reported 3D measurements, using a total station. All other cases only reported vertical deflections. Attendance at NDT/SHM conferences has revealed that most engineers in those fields are unaware of the measurement capabilities of such instruments—not one person in any of the conversations had heard of a laser tracker, and no EDM instrumentation was on the exhibit floors.