March 20, 2006
Minnesota Highway Patrol Uses Image-Based Crash Scene Mapping Technology during Inclement Weather Conditions
DeChant Consulting Services - DCS has reported the adoption by the Minnesota State Patrol (MnSP) of the close-range photogrammetry system iWitness™ as their image-based measuring tool for accident scene mapping and 3D reconstruction. The iWitness system is a stand-alone photogrammetric measurement technique, which produces 3D coordinate data from 2D features recorded in multiple images by a consumer-grade digital camera. Apart from the iWitness software suite, a complete measuring system for accident reconstruction comprises one or more inexpensive digital cameras and special photogrammetric evidence markers for crash scene investigations. MnSP, Major Accident Investigation Team (MAIT) has implemented iWitness across the state.
The Minnesota Department of Transportation (MnDOT) earmarked $16,000 for the implementation of photogrammetric technology by the MnSP throughout its statewide operations. The 3D measurements generated by iWitness are converted into CAD diagrams of the crash, which can subsequently be used for accident analysis or in legal proceedings.
Trooper Jeffrey Westrum from the Major Accident Investigation Team of the Minnesota State Patrol reports "in one snowstorm fatality mapping case, I had the option of driving back to the MAIT office and getting the total station to map the scene. All other state trooper's that morning were assisting in different crashes. The fact that it would have taken at least an hour for me to acquire, and then setup the total station, as well as require the support of another state trooper to help map it, made me decide that utilizing the iWitness photogrammetry method was the best choice. On scene, it only took me approximately 10 minutes to take the required digital pictures of the crash scene for later measurement using the iWitness photogrammetry method. Noteworthy is the fact that it was only my time at the crash scene, and that I didn't need to have a second trooper present to assist, thereby doubling the number of personnel hours needed to document this critical event."
"Using photogrammetry allowed me to document more evidence in a much more detailed manner than what could have been accomplished using a total station. The time it took to measure the critical evidence on the computer and create a scaled diagram was under two hours - back in the warmth of the office in December. The greatest advantage I see in this particular crash, the detail work was done in an office by one person, not in the middle of swiftly moving traffic during inclement weather by two people. Given the cold weather conditions and volume of traffic, I could not have documented as many separate road surface gouges and other evidence that I detailed using the photogrammetry method verses that of a total station or baseline approach."
Trooper Westrum continued to explain "Using the pictures (and photogrammetry) I can articulate key points that were measured on the scene by showing someone a photograph of the scene. Using the iWitness photogrammetry system allows law enforcement to not only show the evidence in the photograph, but the precise 3D measured point location - right on the pictures."
Lee DeChant, President of DeChant Consulting Services, has implemented close-range photogrammetry systems across the US and believes iWitness is the optimal image-based mapping technology for accident reconstruction and forensic measurement, based on its low-cost, robust online data processing and its simple operation. DeChant Consulting Services has assisted numerous state and local police departments by implementing photogrammetry technology, as it becomes a standard for police accident reconstruction and forensic measurement.