Evaluation of Photogrammetry System with Constraints on Camera Position and Attitude for Accurate Shape Measurement of Space Structures

Abstract

Measurement methods based on photogrammetry are highly accurate and effective for large space structures. However, photogrammetry is difficult to use in a thermal vacuum chamber because a remote drive system is required for operating a camera, whose position and attitude must be constrained. The objective of this study is to evaluate the measurement accuracy of a photogrammetry system under camera constraints. We constructed a simplified rail-based measurement system that simulates the circular motion of a camera drive system in a chamber. The camera was constrained to moving on a circular rail that surrounded the specimen, taking photographs at regular intervals along the circumference. We conducted experiments at various camera heights and angles and determined the measurement error. A high measurement accuracy of about 0.02 mm root-mean-square was achieved under appropriate camera conditions. Placing the camera nearly perpendicular to the target was found to improve the measurement accuracy. It was also found that markers were more easily detected on the curved surface of a parabolic antenna than on the flat surface of an aluminum honeycomb plate. The results indicate that accurate photogrammetric measurements in a thermal vacuum chamber are possible, even with constraints on the camera position and attitude.