3-D modelling of historical sites using low-cost digital cameras

Photogrammetry is the art and science of deriving accurate 3-D metric and descriptive object information from multiple analogue and digital images. Recently, there has been an increasing interest in utilizing imagery in different fields such as archaeology, architecture, mechanical inspection, and surgery. The availability of reasonably priced, off-the-shelf, and high-quality digital cameras is encouraging such interest. Any camera needs to be accurately calibrated and tested before it can be used for accurate derivation of 3-D information. Traditional camera calibration is performed by qualified and trained professionals using a test field with numerous control points (i.e., points with known ground coordinates). To expedite the process of camera calibration, this paper outlines a new approach that is based on linear features within an easy-to-establish test field. Therefore, non-photogrammetrists can utilize the new calibration procedure with the least effort. Moreover, the simplicity of the calibration procedure allows for the evaluation of the camera stability through analyzing the estimated internal characteristics of the implemented camera from repetitive calibration sessions. The proposed technique is considerably more flexible and possesses higher degree of robustness when compared with traditional camera calibration exercises. The introduced calibration methodology allows for the utilization of digital cameras in a vast range of application areas (e.g., three dimensional archiving of models and monuments as well as the capability of generating 3-D perspective views). This paper introduces the calibration procedure, some analysis of the expected accuracy, and the suggested methodology for 3-D modelling of historical sites. Experimental results using real data proved the feasibility and the quality of the outcome from the suggested approach.