A System for Locating Points, Lines, and Planes in Space

A microprocessor-based system for locating points, lines and planes within a cubic space 50 cm on a side is described and its performance evaluated. The technique is based on measuring the transit times of a shock wave produced by a small electric spark to each of 3 linear orthogonal microphones. Arranging 3 spark gaps in a plane permits the determination of the orientation of lines and planes in space. A technique is described to compensate for air temperature variations which have a direct effect on system repeatability. The effect of random room air currents has been studied. The linearity of the system was measured and found to contain an error of ±0.12 percent of full scale. Overall worst case (99.73-percent confidence interval) system accuracy was found to be 0.08 ± 0.96 mm.