Scanner Maps Collapse Scene

Leica Geosystems redefined the word "support" when it assisted the California Highway Patrol's (CHP) multidisciplinary accident investigation yeam (MAIT) at the recent collapse of a major San Francisco-area overpass. The CHP brought a Leica ScanStation 3-D laser scanner with them to map the scene, and Leica Geosystems dispatched an application engineer to help collect and process the accident scene data.

The accident occurred early on the morning of April 29 when a tanker truck carrying more than 8600 gallons of gasoline crashed on the "MacArthur maze," an approach to the San Francisco-Oakland Bay Bridge, igniting a 3000 °F fire and causing the I-580 overpass to collapse onto an interstate below.

MAIT officers used Leica's ScanStation, which allows data to be acquired remotely, to document critical sections of the infrastructure from a safe distance.

The CHP was on the scene within minutes of the incident. Once it was safe, MAIT members set up the Leica ScanStation and systematically scanned the scene, collecting high-accuracy laser scan data from the ground to the top of the destroyed overpass. Leica Geosystems' application engineer arrived a short time after scanning began and was on hand to help the CHP document the scene.

Recording forensic evidence to map the complex scene was further complicated by contractors demolishing the overpass as MAIT members were scanning it. Lt. Dave Fox, MAIT's team manager, said, "The ScanStation enabled us to be very mobile and efficient while collecting very detailed data. Typically, we can acquire 500 to 1000 points; with Leica's 3-D laser, we collected millions. We couldn't have collected that kind of information without laser scanning."

Leica's ScanStation also made the job of collecting data safer, said Tony Grissim, Leica Geosystems' forensic account manager. "There were many areas at the scene where it was unsafe to walk. Since Leica's ScanStation allows you to acquire data remotely, MAIT officers could document critical sections of the infrastructure from a safe distance."

Grissim also facilitated interest in and support of Caltrans (California's DOT) to use the high-accuracy scan data for its ongoing analysis and reconstruction of the overpass failure. Once the CHP finished scanning the scene, Leica Geosystems' application engineer acquired a copy of the data and hand-delivered it to Caltrans the following morning; the company also provided Caltrans and the CHP with technological resources and expertise for their investigation. Caltrans intends to make the scan data available to the public on the Web using Leica Geosystems' free TruView point cloud (a type of surface model make up of individual points) viewer.

For more information, visit: www.leica-geosystems.us