Photogrammetry and laser scanner technology applied to length measurements in car testing laboratories

The important reforms developed in vehicles require geometrical measurements in car testing laboratories. They are usually performed by using coordinate measuring machines in gantry configuration or laser trackers. The uncertainty values obtained from this instrumentation is very low in comparison with the high tolerances required by the standards applied to the measurements, UNE 26-192:1987 and ISO 612:1978. This fact, together with the requirements about economical investments, lead to the research of the suitability of different metrological systems and procedures. Photogrammetric and laser scanning systems require lower economical investment so they can be useful in car testing laboratories. In this work, two of these systems are tested to verify their capability to fulfil the parameters and tolerances required for the standards UNE 26-192:1987 and ISO 612:1978. The uncertainty evaluation of these techniques is performed using a standard artefact based of five delrin spheres which is previously calibrated using a coordinate measuring machine. Geometrical parameters height, length, width, front track and wheelbase are measured from a car using the techniques under study, and MATLAB software aided in data processing. The results obtained are compared with the geometrical data previously provided by the manufacturer and the tolerance and uncertainty intervals defined by the standards. Both techniques demonstrate their metrological capacities for the performed measurements and required tolerances, although photogrammetry appears as a more advisable technique. Photogrammetry requires lower economic investment and offers higher portability, although human operator requires more expertise for target positioning and illumination controlling. (C) 2011 Elsevier Ltd. All rights reserved.