Geometric Calibration of the Digital Large Format Aerial Camera Ultracamd

The evaluation of the geometric performance of the novel digital large format camera UltraCamD is the topic of this presentation. We describe the concept of the geometric calibration by means of a bundle adjustment. Based on the specific design of the camera additional parameters were defined and the bundle adjustment software BINGO was modified in order to handle these parameters. The entire calibration procedure consists of four phases. In the first phase a set of images of a well defined geometry target is taken in such way, that highly redundant observations are possible. The second phase is dedicated to image coordinate measurement. Automation and accuracy is derived by image processing techniques exploiting the specific shape of the well defined targets. The third phase consists of the semi automatic adjustment process, where unknown parameters of the camera (e.g. focal length and principal point coordinates, distortion parameters and additional parameters) are estimated. In phase four we distinguish between linear and non linear parameters. Linear parameters are used to reduce the linear effect of distortions of the camera. This is achieved by a linear transform of the measured coordinates in such way, that only small nonlinear effects remain. Those effects are then described in a look up table. The results from a full calibration campaign, the adjusted parameters and the effect of these parameters are presented. Finally the calibration is approved and justified.