How Total Stations and Laser Scanners Can Work in Tandem on Crash Scenes
Crash scene investigations present multiple challenges for police officials. Scene integrity and evidence must be preserved while still allowing first responders to carry out important and often life-saving work. Accident scenes, especially large ones, require extensive and time-consuming data collection and mapping. Investigators must be kept safe from scene hazards and distracted or impatient motorists. At the same time, it is imperative that roadways be reopened as quickly as possible. In order to speed the process, some police agencies are now combining two distinct mapping technologies to create a streamlined workflow that significantly reduces data-collection time and accelerates the reopening of roadways.
Crash Scenes Require Hours of Processing
In a fatal vehicle crash investigation, police interview witnesses and take photographs. They also create a plan view sketch. The plan view sketch, which is the primary piece of evidence in a crash scene, is usually completed with a robotic total station depending on the number of vehicles involved, the complexity of the scene, and the distance covered. The combination of these varying factors can easily equate to hours of mapping time.
Take, for example, a typical intersection accident in which two cars collide and someone dies. This is considered a minimal scene, and it will take 90 minutes to two hours to map plus another hour or two to conduct interviews, take photographs and complete other duties. In all, the road will be closed three to four hours. Usually, people don’t get too upset about that timeframe. However, if a crash occurs on a major highway of a large city and traffic is at a standstill for eight to 10 hours, everybody—from the governor down—is going to be screaming.
Combining Technologies Can Streamline the Workflow
Conventionally, robotic total stations are used to map key evidence as well as all the lane lines, pavements, view obstructions, dividers, etc., which is a laborious and time-intensive process. To speed the mapping process, some police agencies are deploying robotic total stations in tandem with high-definition 3D laser scanners to streamline their workflow. This new model utilizes each instrument according to its strength—the robotic total station because it’s so familiar and the laser scanner because it’s so visual. This streamlining reduces mapping time and, thereby, road closure time by six hours or more.
The new workflow separates the mapping of key evidence from the mapping of the crash scene. The robotic total station is deployed only to collect key evidence such as skids, scuffs and points of impact. The robotic total station can collect this critical data in less than one hour with 2 mm accuracy. Afterward, the laser scanner is deployed to quickly capture everything else with 4 mm accuracy. In less than 15 minutes, the scanner captures a preliminary survey of the crash scene showing all of the important features of the road, including points of rest, lane lines, pavements, view obstructions, dividers, etc., in a single scan. While important, these features are not usually primary pieces of evidence. Nevertheless, the visual context they proved is useful in an investigation.
The Results Are Easy to Explain in Court
This streamlined workflow is a field-to-finish solution that is economical, easy to learn and implement, and simple to explain in court.
The logic behind the new workflow is that each scanner occupation is unique and stand-alone. Multiple scans, which may be required for large accident scenes, are not registered to create the entire scene. Instead, each stand-alone scan is viewable through clickable bubbles, which function similar to Street View in Google Earth. When clicked, the bubbles display exactly what the scanner saw from the selected point of view. Multiple scans as well as datasets collected with other surveying technologies can be tied in by the use of a simple satellite image indicating where each scan was taken. This eliminates a significant expense in software, training time, and the complicated logic and adjusting, or averaging, of multiple datasets.
The workflow also fits well within the user’s comfort level. Training is very simple. Many investigators already know how to operate robotic total stations. The shortened learning curve and simpler logic facilitates rapid implementation of the new laser scanning technology, especially in agencies with multiple users. In most cases, a complete field-to-finish training can be covered in less than one hour in a workshop-type environment. Then, by repetitive training, the field teams can be comfortable and productive within a day or two.
Finally, everything a law enforcement officer does, especially if it’s death-related, may have to be testified to in court, and the rule of thumb is to make the testimony as uncomplicated as possible. With this new workflow, police are presenting key evidence that has been captured with a robotic total station—a technology for which they already know how to testify. Likewise, since police have been using robotic total stations for at least 15 years, courts are familiar and comfortable with the technology.
Laser scanner technology, in contrast, is a relative newcomer on the criminal justice scene. Even though Leica Geosystems’ laser scanners meet the rigorous Daubert standard and have achieved 100 percent admissibility in court, many courts and jurors are, nevertheless, unfamiliar with laser scanning and require introduction to this state-of-the-art technology. The combined workflow can make this introduction easier. By having a single scan unto itself, the explanation of relationships between objects is simple because the data never changes. Jurors may also find it easier to understand what happened when the scene is shown from the static perspective of the scanner.
The deployment of robotic total stations in tandem with laser scanners creates a streamlined workflow that significantly reduces crash scene mapping time and speeds the reopening of roadways. While this workflow is not the high-end approach needed for crime labs, it does accomplish the basic crash scene documentation needs for many police agencies. It also has the added benefit of enabling investigators to stay within their comfort zone and, at the same time, ease into laser scanning—a technology that is quickly revolutionizing the criminal justice system.
For more information on this workflow, please contact us.