The Accuracy of an Optimized, Practical Close-Range Photogrammetry Method for Vehicular Modeling

Three targeted vehicles of varying size were measured using an optimized, practical photogrammetry technique and the results were compared to measurements acquired via total station. The photogrammetry method included the use of a field-calibrated DSLR camera equipped with a fixed 20 mm lens, retroreflective targets sized for vehicular modeling, and a CNC-machined scale bar. Eight photographs were taken from proper angles and processed using a commercially available photogrammetry package. This data was merged with the total station data using a cloud-to-cloud registration process for point-to-point comparison of positional data. The average residual between corresponding photogrammetry and total station points was 1.7 mm (N = 258, SD = 0.8 mm) with a 95% confidence limit of 3.1 mm. Considering this low residual, one of the sample vehicles was re-measured using a high accuracy FaroArm for comparison to the photogrammetry technique. The average residual between corresponding photogrammetry and FaroArm points was 1.2 mm (N = 83, SD = 0.56 mm) with a 95% confidence limit of 2.1 mm. This research shows photogrammetry can be highly accurate and efficient with proper methodology, while also expanding on the photogrammetry literature database and improving confidence in the technique.