Abstract
Regular inspections of sewer systems and pipelines are crucial for maintaining functionality. Since many structures are not directly accessible, a robotic platform equipped with a camera ring and laser scanner is employed. This paper presents a novel hybrid image stitching pipeline with a geometry-driven decision process that combines model-based and simplified geometric approaches to generate unwrapped pipe textures from homogeneous, featureless images. In the model-based method, each camera image is projected onto a 3D pipe surface reconstructed from the laser scan and then unwrapped. This enables geometrically consistent texturing for complex geometries with deformations, house connections or deposits, but is computationally expensive. The main contribution is a real-time capable hybrid pipeline that combines the model-based method with a simplified stitching approach and automatically selects between them based on the scanned geometry and a strict time budget on embedded hardware. If the laser scan confirms that the sensor head is approximately parallel to the pipe axis and the upcoming pipe segment is close to a perfect cylinder, the simplified stitching method is used. In this case, the overlap between camera images is computed directly from the measured distance between each camera and the pipe wall and the camera’s opening angle. Both stitching approaches use the same laser scanner. The appropriate method is selected automatically based on the scanned geometry. The simplified method reduces computation time by about 50% compared with purely model-based stitching. Together with the decision process, this enables real-time pipe texture generation and demonstrates the feasibility of onboard defect analysis on embedded hardware.