GORS 15 - 1 Studying the possibility of using non-metric digital cameras in determining the geometric properties of small objects

Abstract

Abstract: The rapid technological development in the production of commercial digital cameras with different resolutions and low prices, motivates studying the possibility of using them in different applications of close range photogrammetry. In this study, two types of non-metric digital cameras (Canon PowerShot SX20 IS, Olympus C220Z) are used to determine the geometrical properties of small objects by reconstructing a three-dimensional model of these objects using close range photogrammetric techniques which provide high accuracy and with minimum costs that is much lower compared to other technologies. The research was carried out in two basic stages. The first stage included the completion of the geometric calibration of the two cameras, with the aim of determining the real values of the internal orientation elements, which include the focal length, and the coordinates of the main points of the image, in addition to the values of radial and decentering distortions of the camera lens used, which affect the location of the point in the image, Thus, it in turn affects the values of the calculated ground coordinates from the measurement on the image. Whereas, the second stage included the regeneration of the three-dimensional digital model of the studied object based on the methodology of multi-image surveying, according to annular paths, which focuses on taking many images of the studied object, so that each of the points of the studied object appears on two images, at least according to a specific rules referred to in the research, and to adjust the bundle of the images that we obtained by way of bundle adjustment, and using the coordinates of a number of control points and check points calculated within a network of local reference Cartesian coordinates were designed in proportion to the case studied. At the end of the research, based on the generated model, the size of the studied object was calculated, and its accuracy was evaluated compared to its actual size, as an example of the geometric properties that can be calculated for the studied model. The study showed a high effectiveness of adopting this technique using this type of camera, as the accuracy of determining the coordinates was less than (± 2mm), and with a relative error in determining the size ranged between (± 0.035) to (± 0.076).