Verification artifact for photogrammetric measurement systems

Abstract

A low-cost mechanical artifact is developed for the metrological verification of photogrammetric measurement systems. It is mainly composed of five delrin spheres and seven cubes manufactured in different sizes. A set of circular targets are fixed on these elements to perform the photogrammetric restitution. The artifact is used in order to compare three photogrammetric systems defined by three different cameras (Canon 5D with 14-mm lens, Nikon D200 with 20-mm lens, and Jai BB500GE with 8-mm lens). Photomodeler Pro and Matlab software are used for the data processing. The precision of the systems is evaluated using the standard deviation of the geometric coordinates calculated from the restitution of the circular targets. The accuracy is calculated using two different procedures: one of them uses the distance between the center of the spheres and the other uses the distance between the faces of the cubes. The comparison between the photogrammetric systems and their associated calibration files reveals that the Jai camera produces the best results in terms of precision and accuracy, while the Canon camera produces the poorest ones. The bad results from the Canon system are primarily related to the low quality of the calibration procedure.