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Integrating Laser Scanning and UAV Data gives Investigators a New 3D view

When it comes to technology, Washington State Patrol (WSP) detectives are fearless. They regularly experiment with tools and software to find innovative ways  to use technology. That technology versatility helps give them the comfort and confidence to respond to any incident and investigate it thoroughly. They needed a hefty dose of both for the massive 2017 DuPont train derailment outside Tacoma, Wash. The incident not only challenged WSP detectives, it  provided the opportunity to push the limits of one of their newly developed forensic tools: an integrated scanning/UAV point cloud.

On the early morning of Dec. 18, 2017, an Amtrak passenger train was making its inaugural run between Tacoma and Portland, Oregon. As it neared a curve leading to an Interstate-5 overpass near DuPont, the lead locomotive, along with 11 of its 14 rail cars, derailed; four cars landed on Interstate-5, causing a 14-vehicle pile-up. Three of the 77 passengers onboard the train were killed, 62 passengers and six crew members were injured. Damage estimates were $40 million. 

Detective Eric Gunderson, the WSP’s technology liaison, led the accident reconstruction phase, bringing in four Trimble TX5 scanners and one UAV. He dispatched two teams per each of the four TX5 scanners and split them into two groups, one to work on the overpass section and one to manage the roadway section. Both groups followed the same process. Starting at each end of the scene, they moved towards each other, scanning individual rail cars, strewn debris, vehicles, roadway, tire marks, paint marks––any object within the accident scene. In total, the four teams collected 82 scans and more than one billion data points in five hours. While the teams were scanning the tracks and roadway, Gunderson flew the scene with the UAV. He collected 682 photos in 89 minutes.


To prepare the 3D point cloud, he imported the 82 scans into Trimble RealWorks® Forensics software, technology that allows investigators to quickly register, segment and classify 3D laser scan data for analysis and reconstruction. With data from four different scanners, Gunderson had to first group and register, or stitch together, all scans from each scanner to produce four scan-data groups. Then he merged each of the four groups to create one overall point cloud. Since teams were collecting data  during the  active accident investigation, the scanners also captured the hundreds of responders working the scene, resulting in superfluous or “parasite” points.

RealWorks provides automated clean-up tools to help clear unneeded points. With the automatic classification feature, he moved irrelevant objects into designated layers and removed the parasite measurements from the finished point cloud.  

From there, Gunderson focused on importing the  processed UAV point cloud into  the  RealWorks  point cloud. Once imported, he used the automated extraction tool to clean up and remove any superfluous points and then combined the dataset with the master point cloud to produce the final 3D model of the train derailment "Integrating UAV data into RealWorks is nearly seamless because the software views the data as a .las (laser scan) file,” said Gunderson. “Pairing the tops of the train cars from the UAV data with the scanning data of the cars gives us a complete view of the incident scene, and one we wouldn’t have if we had just used one technology.”

The final point cloud result of the DuPont train derailment not only demonstrated the success of Gunderson’s multi-pronged approach on a large scale, it helped cement these technologies as core data sources for the WSP. Earlier this year, the department upgraded their scanners and acquired several Trimble X7 laser scanners. They also launched a UAV pilot program and outfitted 15 collision technology specialists across the state with smaller UAV units. In a job that demands that officers and investigators are ready for any possible scenario at any time, enabling technology is a welcome tool. “RealWorks’ ground extraction tool is excellent. Its clean-up tools enable me to almost freeze the incident scene, which gives us more confidence when investigating after the fact.” — Detective Eric Gunderson, Washington State Patrol.