Integrating laser scanning and UAV data gives investigators a new 3D view
The 2017 DuPont train derailment outside Tacoma provided investigators the opportunity to push the limits of an integrated scanning/UAV point cloud approach
By Mary Jo Wagner
No one would dispute that courage is at the core of any police officer. It takes a certain braveness to dress for a job in which every day is a mystery – people could go missing, be hurt, be fatally wounded – and one’s own life could be at risk of injury or worse.
For Detective Eric Gunderson of the Washington State Patrol (WSP), that fearlessness extends to his department’s adoption and use of technology, where WSP officers regularly move beyond spec sheets to discover new and innovative ways to make technology work for them. For example, they once hung a laser scanner upside down through a sun roof to scan the inside of a car. (It worked). This level of comfort with advanced technological tools has come from years of asking “What if,” and the willingness – from the chief down – to embrace technology that can benefit both the WSP and the citizens the department serves.
Laser scanners have been in the field for the past four years and, in 2017, WSP began adding unmanned aerial vehicles (UAVs) to its technology arsenal.
“Whenever we acquire new equipment, my captain always says that this technology is another tool in your toolbox,’” Gunderson said, who serves as the WSP's technology liaison. “So, if you need a Phillips [screwdriver], you've got one. If you need a flat head, you've got one. No one tool will solve all your needs. It’s important to get comfortable with many different tools both in the field and back in the office.”
Indeed, Gunderson’s penchant for experimentation has been key to becoming at ease with technology. Case in point: soon after acquiring his first UAV, Gunderson tested the possibility of merging scan and UAV data of the same scene into one, integrated point cloud. It was not only a success, but the integrated forensics view has become a formidable tool for accident reconstruction cases, which make up 65% of their responses.
“Individually, both laser scanning and UAVs have their strengths and benefits in the field,” Gunderson said. “But the ability to seamlessly combine the two different data sources into one point cloud gives us a complete 3D view from all sides of a crime scene. That is an additional and powerful forensics tool. The technological versatility we have makes us confident that we’ll be able to respond to any incident and investigate it thoroughly.”
It was that same level of comfort with technology that gave WSP responders the confidence to answer the call to the 2017 DuPont train derailment outside Tacoma, Washington, which was an accident so unpredictable and massive that no training drill could have adequately prepared them. It not only put the WSP to the test, it provided the opportunity for Gunderson to push the limits of the integrated scanning/UAV point cloud approach and display it on a national scale.
Responding from all sides
On the morning of December 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 train was traveling at 78 mph – 50 mph over the speed limit – and the lead locomotive, along with 11 of its 14 rail cars, derailed. It was 7:33 a.m. and I-5 was already teeming with commuters. The lead locomotive and three rail cars landed on I-5, causing a 14-vehicle pile-up. Three of the 77 passengers onboard the train were killed, and 62 passengers and 6 crew members were injured. The initial damage was estimated to be $40 million.
“Where this happened couldn’t have been a worse spot as far as impact to the region,” Gunderson said. “I-5 is the major artery between Tacoma, Olympia, Portland and Seattle. With Puget Sound to the west, the Nisqually River to the south and a military base to the east, your only driving option is I-5.”
WSP troopers were on scene within five minutes of the crash. By 8:30 a.m. the scene was swarming with hundreds of officers, detectives, firefighters and paramedics, all with one thing on their mind: rescue.
“For that kind of incident, the last thing you’re thinking of is preserving evidence,” Gunderson said. “If I need to move a train or car to get someone out, that’s what’s going to happen. Our first hour was consumed by lifesaving, but once we cleared the scene, everything began to slow down, and we could start investigating. Then we owned the scene.”
Working in collaboration with the National Transportation Safety Board (NTSB), the lead investigating organization, Gunderson led the accident reconstruction phase, bringing in four Trimble TX5 scanners and one DJI Matrice 200 UAV. Although he had been merging scan and UAV data into point clouds, he had never applied the approach to an incident of this magnitude.
Teams of WSP collision investigation detectives first walked through the debris-riddled scene, taking photographs, painting the footprints of important objects such as cars and tire marks, and documenting them. In parallel, Gunderson dispatched two teams per each of the four scanners and split them into two groups, one to work on the overpass section and one to manage the roadway section.
Setting up on each end of the tracks, the railway teams methodically moved toward each other, scanning all four sides of the individual rail cars and any strewn debris, and recording each object as it was found. The ground crew followed the same process. Starting at each end of the I-5 scene, the teams collected data points of the rail cars, vehicles, roadway, tire marks, paint marks and anything within the boundaries of the accident. In total, the four teams collected 82 scans and more than one billion data points in five hours.
“What’s awesome about scanning is that it ensures you don’t miss anything,” Gunderson said. “At the accident scene, you only get one shot to get what you need. You can’t put the trains back where they used to be, so you need to be right the first time. Scanning captures everything incredibly quickly and often captures something you didn’t know you’d need.”
While the teams were scanning the tracks and roadway, Gunderson flew the 920-ft-long by 340-ft-wide scene with the UAV. After a 10-minute set-up, he flew an overall pass at 200 ft. at roughly 70% front lap and 50% side lap to establish a base. He flew a second pass at 100 ft. and a final flight at altitudes between 15 ft. and 50 ft. to acquire some oblique photos. In 89 minutes, Gunderson collected 682 photos with the unit’s 20MP camera.
“I could have handled the accident with just one technology, but given its scale, I wanted to have data redundancy,” Gunderson said. “The drone would provide different view angles since the scanner can’t get the top of the train. In addition, with the volumes of data I’d collect, it would be a great opportunity to test how well I could merge the two massive datasets together.”
By 2 p.m., Gunderson was able to pack up the gear and head back to the office to process the data.
Creating a 3D picture
For efficiency, Gunderson loaded the UAV photos into the department’s photogrammetry software for batch processing overnight, so when he returned to the office the next morning, the data would be ready.
Preparing the 3D point cloud began by importing the 82 scans into Trimble RealWorks Forensic software, which allows investigators to quickly register, segment and classify 3D laser scan data for analysis and reconstruction. As there was 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.
With the laser scan point cloud complete, 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. The two came together perfectly, he says.
In total, it took Gunderson about nine hours to create the finished incident model. In less than 36 hours after the initial derailment, he was able to provide a 3D view of the entire accident scene and any object in it to the NTSB.
The NTSB is expected to issue its final report on the accident in 2019.
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Value for money
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.
“The benefits of the laser scanner and the UAV are unparalleled, both individually and together,” Gunderson said. “I can’t fly the UAV in a house, but I can definitely scan it. But if I have a mile-long accident scene, I can fly that in five minutes, and I can supplement with the scanner. I can capture great scanning data at each end of the scene and then connect the two. Having these choices allows us to tackle any scene.”
Last summer, the department upgraded its scanners. The new units give them 500,000 points per second, better intensity detail, which makes objects stand out more clearly, faster scanning and the ability to scan in the rain – an important feature for the Pacific Northwest.
WSP also launched a UAV pilot program last July and outfitted 15 collision-technology specialists across the state with smaller UAV units. The aim was to assess whether the technology could help them map straightforward accident scenes more efficiently and accurately. Soon after the pilot began, a team responded to a one-car pedestrian accident on I-5. Prior to the UAV, they would have worked the scene for a few hours with traditional baseline methods. Using the UAV, they cleared the scene in 18 minutes.
“Someone from the state DOT (Department of Transportation) once told me that any time the I-5 is shutdown, the cost to the region is about $350-$400 a minute,” Gunderson said. “That adds up to a big number really quickly.”
Based on the success of the pilot, the WSP is adding 75 smaller UAVs to its force this summer and more than 50 WSP detectives have been issued the smaller UAVs – each criminal investigation division has a Matrice UAV.
It’s clear the WSP’s commitment to asking, “What if” and investing in technology tools is not abating. In a job that demands that officers and investigators are ready for any possible scenario at any time, enabling technology is a welcome tool.
“Pushing the envelope with our technology is having a huge impact,” Gunderson said. “We could never have trained for an incident like the derailment. But when it happened, we didn’t hesitate to respond because we knew we had the technology and tools we needed. You’re going to have victims who want answers and investigators who must give those answers. Our ability to provide information that will help people find the answers feels good. And that’s real value for money.”
About the author
Mary Jo Wagner is a freelance writer who has been covering the geospatial industry for 25 years. Contact her at firstname.lastname@example.org.