The Potential of a Low Resolution Digital Camera in Close-Range Photogrammetry

Abstract

The primary purpose of this dissertation was to study the potential and accuracy aspects of digital photogrammetry in close-range applications. The algorithms and softwares for control point measurement, conjugate epipolar lines computation and digital image correlation were developed. An experimental study was conducted with two GE TN2500, 244 x 248 pixels, CID digital/analog cameras for the mapping of a small object. The result showed that two-dimensional (2-D) correlation was significantly more effective than one-dimensional (1-D) correlation, and that the positioning precision of digital correlation improved significantly with array size up to an array of 5 x 5 pixels. Increase in array size beyond 5 x 5 pixels did not result in any improvement in positioning precision for the system used in this study. Circular targets were used as control points. The image coordinates of these control points were calculated using two different procedures: (1) digital pointing, and (2) digital correlation. The two procedures were found to yield similar precision. Contour lines generated by digital correlation were found to be in good agreement with those obtained by conventional approach using a 35mm camera for photography. The results of this investigation demonstrated that low resolution digital array cameras could be used to achieve a mapping accuracy comparable to that of conventional 35mm cameras. The study showed that the basic technology exists for development of a totally automatic mapping system.