Earth, Wind and Fire: The application of Photogrammetry for Challenging Large Scale Metrology Projects

Abstract

This paper describes the photogrammetric measurement of three large scale objects. The objects, a 21m antenna, a 43m wind turbine blade mold and an eight meter gas turbine were all measured during the course of a single week. The customer measurement requirements for each of these objects was very different, but they shared the common requirements of very high accuracy, very short time windows for measurement and challenging environmental conditions. The first object, a 21m panel antenna is located in Ulsan, South Korea. The antenna is part of the Korean Very Long Baseline Interferometry Network (KVN). The surface RMS requirement for the antenna was of the order of 60m. The antenna site is quite remote and a crane was required to lift the camera and operator some 10-20m above the antenna surface. Measurements took place at night to minimize the diurnal effects of heating and cooling of the antenna surface. The 43m wind turbine blade mold is located in Baroda, India. The principal requirement was to measure the complete surface of the mold as quickly and as 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 last object, an 8m long by 6m high gas turbine is located in Pusan, South Korea. The primary objective of the 3D coordinate measurements was to characterize the behavior of the gas turbine as it went from 0% to 50% to 100% power.