Automatic Correspondences for Photogrammetric Model Building

The problem of building geometric models has been a central application in photogrammetry. Our goal is to partially automate this process by finding the features necessary for computing the exterior orientation. This is done by robustly computing the fundamental matrix, and trilinear tensor for all images pairs and some image triples. The correspondences computed from this process are chained together and sent to a commercial bundle adjustment program to find the exterior camera parameters. To find these correspondences it is not necessary to have camera calibration, nor to compute a full projective reconstruction. Thus our approach can be used with any photogrammetric model building package. We also use the computed projective quantities to autocalibrate the focal length of the camera. Once the exterior orientation is found, the user still needs to manually create the model, but this is now a simpler process.