Three-dimensional data capture system for stereo-video images

This paper describes one of the industrial applications of our digital photogrammetric system VirtuoZo, namely a prototype system to collect 3D data from stereo-video pair sequences along a rail road track for clearance measurements. With the rapid developing of digital media such as charge-coupled-device (CCD) and digital video cameras, stereo images pairs can be captured in a much easier and faster way compared with traditional means. Digital photogrammetry can thus now be used in many new applications. However, with the geometry of CCD (or digital video) cameras different from the classic analogy metric camera, new relative orientation and epipolar image resampling algorithms have to be developed for these nonmetric cameras. An example of such a new application is given in this paper: a series of sequential stereo image pairs were captured by two digital cameras along a railway track from a moving rail platform, then relative orientation was done fully automatically by matching registering points in the two stereo scenes using a hierarchical relaxation image matching algorithm. Then, epipolar images are resampled from the original images by means of a relative linear transform, and finally a 3D data collection algorithm allows a user-friendly interface to the human operator for data capture on a SGI workstation under StereoView.