Robotic Total Stations and CAD-Based Diagramming Clear the Way for Smoother Forensic Mapping in Minnesota

As Statewide Crash Reconstruction Coordinator for the Minnesota State Patrol, Sergeant Lance Langford is responsible for keeping its reconstructionists not only up to date with changes in vehicles and vehicle technology but also up to speed with the accurate, efficient forensic mapping tools. The last upgrade from tape measures to total stations reduced their mapping average to less than two hours. But with advancements in forensic mapping technology and nearly 600 cases per year, Langford knew they could do better. “When we moved to the Leica TS12 robotic in 2015, we cut our scene time by about 50 percent because you set it up yourself and do all the work yourself,” he says. “It’s a very quick way of doing it, extremely accurate, and it’s simple to use.”

Technical Sergeant Kelly Phillips, of the MSP Metro Crash Reconstruction Unit, agrees. Phillips is one of five full-time reconstructionists in the Twin Cities metropolitan area. Before the transition to robotics, she had to recruit on-scene law enforcement for assistance when working alone. “They don’t know how to use our mapping tools,” she says. With the Leica robotic total station, she now does all the work herself. “I don’t have to tell them, ‘Okay, you’ve got to hold the prism here, you’ve got to do this, and so on,” she says. “I can get out there, map it, and get the roadway back open fast.”

Deadly Winter Collision Reveals Conspicuous Lack of Pre-Impact Evidence 

As the team’s sole reconstructionist with specialized training in heavy trucks, Phillips typically works large complex scenes. The improved workflow was especially beneficial on an intersection crash she mapped in January 2017. In this case, an eastbound passenger vehicle was stopped at a traffic semaphore on a divided four-lane highway when a tractor-trailer truck hit it from behind at freeway speeds. “The passenger car literally just came to a stop for a red light two seconds before impact,” Phillips says. The driver of the car was killed instantly. “Thankfully, the cable barrier stopped the semi from crossing over to the westbound traffic,” she adds. “Otherwise, he would have taken out more cars.”

Winter weather didn’t appear to be a factor. Snow was accumulated along the sides of the highway, but the pavement was clear and dry. “And the road was straight and level,” Phillips says. “There were no vision obstructions—nothing.” The semi’s braking inefficiency didn’t appear to play a part either. In fact, there was no evidence that the truck even attempted to stop. “There was no pre anything—pre skid marks, pre nothing—from either vehicle,” she says. “All we had was a series of gouges and scratches, and then all of a sudden, these tire marks start in the right lane of the eastbound traffic, and now both vehicles are off the road and into the median between the east- and west-bound traffic.”

After Phillips photographed the scene, she began painting the evidence. “Commercial vehicles leave a lot of tire marks.” she says. To differentiate the vehicles, she painted the semi’s evidence with one color and the passenger car’s with another. “That way, we can get an idea of where they were at prior to impact by working backwards from their final rest,” she says.

Next, Phillips brought out the Leica TS12 robotic total station (similar to the newer Leica TS13 model) and began plotting the evidence. As she walked the pole from point to point, the tripod-mounted theodolite automatically tracked the prism’s movements. With the prism in position, Phillips took the shots herself with a handheld data collector running Leica Evidence Recorder. “I could just jump lines and jump evidence type and go from part of vehicle one to vehicle two and then back to vehicle one because I know how to utilize the robotic total station to its full ability,” she says.

It was a complicated scene. “The mapping itself took about two hours just because of how many post-crash pieces of evidence there were, the dynamics between the two vehicles, how the car rotated post-impact and came to final rest, and how the semi-truck continued on through the snow and then struck the cable barriers,” Phillips says. “I mapped everything so I could get a to-scale diagram to place the cars at impact on my diagram later on at the office.” Phillips also decided to map the small gauge marks, even though there were so many. “We got every one of those just to show how much damage this caused to the roadway itself due to how violent it was and how fast it happened,” she says.

End-to-End Capabilities Provide Seamless Workflow from Data to Deliverables

After six hours on scene, Phillips headed back to the office to begin piecing the puzzle together. The Minnesota State Patrol uses Map360 for collision reconstruction. While the desktop software, which is part of the Leica Geosystems Incident Mapping Suite, is powered by an IntelliCAD engine, it is designed with an intuitive interface that allows users to easily import, process, analyze, visualize and create court-ready deliverables with data from any geospatial sensor or manufacturer.

All of Map360 was extremely useful for this case, but what I really like is the wipeout feature. We imported the vehicle as a symbol, outlined the crash profile based off our map, and wiped out that crash profile portion from the symbol so it actually showed the damage on the vehicle. We can match those cars up so much nicer, and it’s just easier to show the angle of impact.

To begin the diagramming process, Phillips plugged the data collector into her computer and uploaded the total station data into Map360. “It took maybe 30 seconds,” she says. “I brought the diagram in to scale, cleaned up the lines so it looked like it was at the scene, brought in the semi and the passenger car, and figured out where the car was prior to impact based on the gouges that it left,” Phillips says.

The CAD-based drawing software is loaded with crash- and crime-scene-related features for accurate analysis and representation. “All of Map360 was extremely useful for this case,” she says. “But what I really like is the wipeout feature.” For the crash profile, Phillips selected exemplar vehicles from the Map360 library. “We imported the vehicle as a symbol, outlined the crash profile based off our map, and wiped out that crash profile portion from the symbol so it actually showed the damage on the vehicle,” she says. “We can match those cars up so much nicer, and it’s just easier to show the angle of impact.”
Based on the damage profile, Phillips placed the car in the right lane and aligned the vehicles to demonstrate that the semi was partially into the right-turn lane at impact. “I was able to show, based off that map, how the car rotated and came to final rest and how the semi continued on its path of travel to final rest. That information is critical when we need distances and rotation for mathematics. We need to know how those cars traveled and how they lost speed or accelerated based off that evidence,” she says. “The diagram is crucial to show those paths of travel.”

Phillips then solved an in-line mathematical equation to determine the semi’s speed at impact. “We get a lot of data out of the mapping program like angles—approach angles, departure angles,” she says. “But for court standards in Minnesota, we have to be able to show our work. We use Map360 to verify, but when it comes to mathematics, we hand write all the math because the court’s going to want to see how we obtained those numbers.”

With the puzzle assembled, the cause of the collision became clear. “We were able to show that the semi driver was not paying attention and that he struck the passenger car at 63 miles an hour and basically killed that driver at impact,” she says.

Sequential Diagrams Help Achieve Felony Convictions

Phillips provided the county attorney with a flash drive of the raw data, the finished map, screenshots, and 12 diagrams, nine of which were used in court.

We need to know how those cars traveled and how they lost speed or accelerated based off that evidence. The diagram is crucial to show those paths of travel.

To convey to the jury the violence of the collision, she included a series of overhead diagrams showing the placement of both vehicles from pre-impact to final rest. “I showed different snippets of how it was at impact, as it started to get pushed through rotation, of the car at separation, the continuation of the semi, the rotation of the car after it became separated, and how it traveled sideways up into the the cable barriers and then came to final rest,” she says. “Showing the rotation through that mapping data was significant because of the injuries it caused the driver and how it basically killed him on impact.”

The magnitude of the collision was also evidenced by the extensive gouge marks in the road surface, which Phillips had taken the extra time to map. “I think that opened the jury’s eyes to, ‘Holy Moly, this really was a bad crash,” she says. “And we were able to get a conviction off of it.”

Based on the forensic evidence Phillips provided and the trucker’s admission that he was distracted, he was found guilty of criminal vehicular homicide and gross negligence and is currently serving a 4-year sentence. “The semi driver was on his phone looking at real estate,” Phillips adds. “He didn’t even see the stopped vehicle until impact.”

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