Earth, Wind, and Fire: The Application of Photogrammetry for Challenging Large-Scale Metrology

Abstract

This article describes the photogrammetric measurement of three large-scale objects: a 21-meter antenna, a 43-meter wind turbine blade mold, and an 8-meter gas turbine, all of which were measured during the course of a single week. The customer’s measurement requirements for each object were very different, but they all shared the requirements of very high accuracy, short time frames for measurement, and challenging environmental conditions. The first object, a 21-meter panel antenna, is located in Ulsan, South Korea. The antenna is part of the Korean Very Long Baseline Interferometry (VLBI) network. The root mean square (RMS) surface error requirement for the antenna during construction was ≤ 60 µm. The antenna sits a considerable distance off the ground and a crane was required to lift the camera and operator 12 THE JOURNAL OF THE CMSC/AUTUMN 2014 as much as 20 meters above the antenna surface. To minimize the diurnal effects of heating and cooling of the antenna surface, measurements took place at night. The second object, a 43-meter wind turbine blade mold, is located in Baroda, India. The principle requirement on this project was to measure the complete surface of the mold as quickly and accurately as possible. The elevated position of the mold, as well as the oppressive heat and humidity of the location, made the measurement very challenging. The final object, an 8-meter long by 6-meter high gas turbine, is located in Pusan, South Korea. The primary objective of this 3D