Rotoweld is based on a patented method to measure and control in real time the penetration of the root pass in open butt joints. Developed by the National Research Council of Canada, the method uses machine vision and adaptive feedback to insure full penetration of the root and therefore a defect free weld. Similar to a welder's eyes and hands, the system digitizes the full image of the weldpool as picked up by a solid state camera, analyses its shape and reacts in real time on welding parameters, constantly adapting to varying conditions such as changes in gap, root face or temperature. The system operating range more than covers the tolerances typical of the average pipe prefabrication shop.