Time budget evaluation for image-based reconstruction of sewer shafts

In this paper we propose a robust real-time image and sensor based approach for automatic 3d model acquisition of sewer shafts from survey videos captured by a downward-looking fisheye-lens camera while lowering it into the shaft. Our approach is based on Structure from Motion adjusted to the constrained motion and scene, and involves shape recognition techniques in order to obtain the geometry of the scene appropriately. We perform a time budget evaluation for the components of an existing off-line application based on previous work and design a real-time application which can be applied during on-site inspection. The methods of our approach are modified so that they can be executed on the GPU. Expensive bundle adjustment is avoided by applying a simple and fast geometric correction of the computed reconstruction which is capable of handling inaccuracies of the intrinsic camera calibration parameters.