Keeping track of everything – accident analysis in 3D

May 12, 2023

New digital methods have led to huge progress being made in DEKRA’s accident analysis in recent years. The latest evolutionary stage is 3D photogrammetry. This permits insights into accident scenes that would quite simply have been unthinkable until recently. Accident analyst Randy Stiegler, 33, provides an in-depth look into his day-to-day work and talks about how methods have changed over time.

The future of the past is already reality today: Randy Stiegler, appraiser at the DEKRA Chemnitz branch, uses 3D photogrammetry to create a virtual image of an accident scene. The scene depicts a semitrailer that has fallen sideways through the guardrail of a bridge and smashed into the ground below. It looks like a dramatic departure from reality. In the computer animation it is possible to rotate and turn the scene in any direction. If you zoom in, individual three-dimensional shards are identifiable on the ground thanks to the incredibly good resolution.

Well-equipped for accident analysis

"Needless to say, this is only possible with the appropriate equipment," the 33-year-old explains. But all that is needed today is a powerful computer, an action cam or a regular digital camera and the appropriate software. “With the camera mounted on a high tripod (such as a selfie stick), you walk around the accident scene in a certain pattern while taking as many pictures as possible. Once they are fed into a computer, the software pieces together the data to create a three-dimensional model," he further describes. This makes it possible to visualize things after the event that would otherwise only have been roughly identifiable or not at all identifiable using conventional methods such as 2D aerial views or even hand-drawn sketches of the accident scene.

Photogrammetry in accident analysis

Accident analysts 30 years ago would not have believed their eyes if someone had shown them a 3D photogrammetric image. Back then, in addition to a tape measure and surveyor’s wheel, a clipboard was used for hand sketches. Today, even long-serving analysts are familiar with the new imaging and measuring method. After all, knowledge of new procedures within the field is shared in regular training sessions. Randy Stiegler then explains the possibilities of 3D photogrammetry. It doesn’t necessarily mean that the new methods are automatically superior to the other methods. A 2D drone shot at a 90-degree angle can provide sufficient information in straightforward cases. "3D photogrammetry really comes into its own in complex
cases," agrees Stiegler, who has well and truly been a specialist in the field since 2016. As an example, he cites accidents in which it is important to establish how the parties involved - or the witnesses - viewed the situation: Was cyclist A, who rode into B's car from the side, able to see it in time? Or were the branches of a bush or a signpost in the way? Was the person in the car able to see more, or was his view also impaired? A 3D model, created in about half an hour at the scene, can clear up matters once and for all. It allows defense teams and judges, and district attorneys in the courtroom to adapt one or several perspectives themselves. This is the real advantage of photogrammetry: It is immediately understandable for every viewer. No defense lawyer in the world can seriously challenge such a well-founded report.”
The 3D models also provide advantages on uneven terrain. This is because hills and dips cannot be portrayed in the 2D aerial view and are difficult to reconstruct manually. Photography with a high tripod is equally helpful, for example, when a drone cannot fly high enough because of low trees covering the accident site. On the other hand, the "modern" method reaches its limits under poor lighting conditions – at night, for instance. Yet Stiegler, a passionate tinkerer, even has a solution for this: special camera settings that are first scanned in via QR code and then imported.

At the cutting edge using 3D photogrammetry

Stiegler demonstrated real enthusiasm for the subject from the very beginning. Even during his mentoring period at the DEKRA Dresden branch, he displayed a keen interest in the reconstruction of a spectacular accident in which a car had careered over an urban embankment and crashed into the roof of a church. “I had installed a free test license for the software on my computer and spent about a quarter of an hour at the scene taking photos with my digital camera,” recalls the young appraiser. “Back at the hotel after work, I fiddled around and performed some calculations until I managed to create a 3D model that allowed me to send the car careering over the embankment at various speeds. Ultimately to find out how fast it must have been traveling to take the necessary flight path. It turned out to be 110 kmh.”
With 3D photogrammetry, which is now used at around 25 branches in Germany, DEKRA is absolutely at the cutting edge – but it has by no means reached the end of its evolution.

3D photogrammetry is my tool of choice in complex cases in particular

Randy Stiegler, accident analyst and appraiser at DEKRA's Chemnitz branch