The Accuracy of Photogrammetry vs. Hands-on Measurement Techniques used in Accident Reconstruction 2010-01-0065

A study was conducted to assess the relative accuracy of two measurement techniques commonly used for vehicle measurements in damaged-based accident reconstruction. The traditional technique of hands-on measurement was compared with the use of photogrammetry for measurement of targeted damaged vehicles. Three undamaged vehicles were subjected to 4 impacts, resulting in 4 damaged areas (two front, one side and one rear). The study's intent was only to examine the accuracy of each measurement technique. The influence of other confounding independent variables such as selection of measurement location on the vehicle, reference line location, and definitions of what constitutes "damage," etc., were controlled for and minimized by using predefined measurement points on the vehicles and prescribed station lines.

The points on each vehicle were measured using both techniques, and compared to baseline reference measurements obtained via a TOPCON GPT-7005i prismless imaging total station. PhotoModeler was employed as the photogrammetry technique, and photographs of the post-impact vehicles were obtained using several different cameras and photographers, including an adjuster with no formal training or instruction in photographing for photogrammetric analysis. Hands-on measurements were obtained via two groups of qualified professionals in the field of accident reconstruction, with access to both the vehicles and traditional measuring equipment such as tape measures, crush jig and plumb bobs.

The results found that both methods effectively measured the vehicle points, with a mean difference between the baseline and hands-on measurements of 0.6 ± 1.4 cm, and a mean difference between the baseline and photogrammetry measurements of 0.1 ± 1.0 cm. The accuracy of the photogrammetry method was found to be slightly greater than that for hands-on physical measurements. The results indicated that both physical inspection of a damaged vehicle and photogrammetric analysis from photographs are suitably accurate techniques for vehicle damage measurement, and in some cases the photogrammetric analysis may even yield superior results.