Digital close range photogrammetry in motor vehicle accident reconstruction

Road traffic accidents are consistently in the top ten causes of death world-wide. In order to reduce the number of fatalities caused by traffic collision, better knowledge and understanding of the sequence of events prior to and during a traffic accident, i.e. Accident Reconstruction, is required, so it is important to obtain detailed quantitative information about the damage sustained by the crashed vehicle(s). The research reported here was aimed at developing a fast and accurate method of measuring the damage. Digital Close Range Photogrammetry is the technique chosen for obtaining vehicle profiles from which accurate measurements of crust damage could be made. These profiles can provide valuable information about the collision. They can be used to find the orientation(s) of the vehicle(s) at the moment of impact. The orientation of the vehicle is used to determine the direction of the principal force acting on the vehicle as a function of the relative velocity vector. The depth of the damage sustained can be measured from the profile: this is used to calculate the energy absorbed by the structure from which the pre-impact speed can be calculated. The photogrammetric measuring method is compared with other techniques, for accuracy and speed. A direct comparison is made with the results obtained from Coordinate Measuring Machine and tape measurements. Consideration is given to errors that arise from the reconstruction of three-dimensional space from two dimensional images. The optimal lighting conditions for best results are studied and results are discussed. In addition the repeatability of photogrammetric modelling is evaluated. The technique is applied to vehicles involved in collisions; the photogrammetric models are used to determine the profile of what the vehicles struck and the pre-impact speeds. It is concluded that close range digital photogrammetry is a fast, accurate (12.4mm) and inexpensive (€2000) method of measuring crush damage and hence of considerable benefit in accident investigation