David Dustin & Eugene Liscio, P. Eng.
Abstract: The need for quick and versatile scene documentation tools continues to be of great importance at both crime and accident scenes. What was once documented by hand has transitioned to the total station and, most recently, the laser scanner due to its ease of use and capacity to quickly document millions of data points for a more complete documentation of the scene. Both the laser scanner and total station have been accepted in courts all over the world and are in use at police agencies globally. However, few studies, if any, exist that look at the accuracy and repeatability of these laser-based instruments in practice. Therefore, this validation study shows that under controlled conditions for an indoor scene with an expanse of approximately 60 m, the total station exhibited a mean absolute error of 1.1 mm. The laser scanner had similar results using a targeted and targetless registration approach and exhibited mean absolute errors of 1.3 and 1.0 mm, respectively, under the same environmental conditions. All three tests performed for each setup/instrument showed an average standard deviation below 0.5mm. For most crime and accident scene documentation purposes, these results are well within acceptable ranges. Depending on the type of environment, object surface properties, number of scans, distance being measured, choice of setup parameters and other factors, these accuracy values may vary.