Stability analysis and geometric calibration of off-the-shelf digital cameras

Recent developments of digital cameras in terms of the size of a Charged Coupled Device (CCD) and Complementary Metal Oxide Semiconductor (CMOS) arrays, as well as reduced costs, are leading to their applications in traditional and new photogrammetric, surveying, and mapping functions. Such cameras require careful calibration to determine their metric characteristics, as defined by the Interior Orientation Parameters (IOP), which are essential for any photogrammetric activity. Moreover, the stability of the estimated IOP of these cameras over short and long time periods has to be analyzed and quantified. This paper outlines the incorporation of straight lines in a bundle adjustment procedure for calibrating off-the-shelf/low-cost digital cameras. A framework for automatic extraction of the straight lines in the images is also presented and tested. In addition, the research introduces new approaches for testing the camera stability, where the degree of similarity between reconstructed bundles using two sets of IOP is quantitatively evaluated. Experimental results with real data proved the feasibility of the line-based self-calibration approach. Analysis of the estimated IOP from various calibration sessions over long time periods revealed the stability of the implemented camera.