Crash scene analysis: testing Pix4D’s solution for forensics
Road traffic accident investigations require speed, accuracy, and reliable data collection. At the Czech Technical University in Prague, transportation experts are exploring how to improve the process with modern technology. Their latest research project evaluates whether mobile 3D scanning tool PIX4Dcatch can document crash scenes faster and more efficiently than traditional methods while maintaining the requisite accuracy
PIX4Dcatch integrates automated data collection, positional tracking, and LiDAR scanning plus photogrammetry, making accurate 3D reconstruction easy and accesible.
Forensic accident reconstruction
Crash scene analysis involves performing on-site measurements to gather detailed evidence that can be used to determine how and why a crash occurred.
By documenting vehicle positions, roadway marks, debris, and other details, investigators can reconstruct the collision, identify root causes—such as driver error, mechanical failure, or environmental factors—and provide objective, measurable data that can be used in court or for insurance claims.
Traditional tools can be costly and time-consuming, while the PIX4D forensics solution (data from PIX4Dcatch with an RTK device and/ or a drone, and processing with [PIX4Dmatic]) offers a streamlined approach for capturing and processing accurate 3D scene reconstructions.
With the ability to merge ground and aerial data, this workflow provides a practical solution for comprehensively documenting accident sites quickly and with precision.
Why speed and accuracy matter
Traffic accidents are time-sensitive. Evidence disappears quickly, and investigators must collect data quickly in order to keep traffic flowing and ensure safety. Because of this, while detailed, accurate data is essential, reducing the time required for accident resolution is equally critical. With this mind, the team saw PIX4Dcatch’s rapid data capture as a potential game-changer for accident site reconstruction.
Given its efficiency, lower cost, and ease of deployment compared to traditional tools, the next step was to assess how its accuracy measures up, as forensic investigations rely on precision to ensure reliable reconstructions.
Putting Pix4D to the test
The team conducted a comparative study, testing Pix4D’s forensic technology alongside total stations, laser scanners, GNSS receivers, and drone photogrammetry. They evaluated how well critical accident scene details could be captured in terms of accuracy, reliability, and efficiency, compared to established forensic workflows.
At the test site, they meticulously documented the accident scene, recording the positions of critical elements related to the incident. The study also examined how well the solution could capture vehicle deformations and interior damage, determining whether Pix4D technology could complement or even replace existing data collection methods used by law enforcement and forensic experts.
To evaluate the workflow for professionals, the research team conducted over 35 measurements and processed over 100 projects, varying in size and complexity (scope of area, object size, image number—ranging from 30 images to more than 1300 images). They focused on three main tasks:
- Reconstructing the accident scene
- Documenting vehicle deformations
- Reconstruction of the vehicle’s interior after the accident
For the team, a key strength of Pix4D’s forensic workflow is its ability to accurately document vehicle deformation after an accident. The solution's effectiveness depended on two deciding factors for the team—how completely it captures data, and how precisely it records damage. They conducted a detailed study to evaluate its performance.
The study
They used an iPhone 14 Pro and an iPhone 15 Pro, both with RTK devices for accurate, georeferenced data. Data processing was done with PIX4Dmatic with follow-up analysis using PIX4Dsurvey.
The study focused on three key data collection aspects:
- Different capture settings: including image methods, accuracy, surface impact, and control points for reducing measurement deviations
- Overall capture and precision: Overall capture and precision: testing Pix4D’s ability to document vehicle damage and positioning in low-visibility conditions, assessing both overall damage capture and precision in detailed areas, such as rear-end impacts
- Capturing interiors the study explored whether Pix4D’s potential for capturing vehicle interiors and object placement after an accident—an area where traditional methods rely on simple photography this test explored whether Pix4D could offer a more accurate and efficient solution
Comparative measurements were conducted using equipment from the Department of Forensic Experts in Transportation
Secure data processing for forensic analysis
Forensic analysis requires strict control to protect privacy and sensitive case data. To ensure security, desktop processing with PIX4Dmatic was chosen over Pix4D's popular cloud solution, PIX4Dcloud. The local data storage of PIX4Dmatic ensured the privacy of sensitive data. The team highlighted the user-friendly interface and noted that the software requires no advanced photogrammetry expertise. They also appreciated its rapid development pace, with one to two updates being released monthly throughout the project duration.
How effective is the Pix4D forensic solution?
Despite challenges like adverse weather, poor lighting, and limited site coverage, the solution proved highly effective for documenting smaller traffic accidents. It significantly reduced measurement time compared to traditional methods, while processing time and hardware demands remained manageable.
“A key benefit is the ability to complete all processing and export results directly within Pix4D software after data import” - Zdeněk Svatý, Ph.D.CTU in Prague, FTS
Tests confirmed that Pix4D is a highly effective solution for police and forensic workflows, providing rapid, detailed documentation of vehicle deformations. The results demonstrated that Pix4D successfully meets both criteria the team aimed to evaluate—completeness of data collection and accuracy in recording damage.
The use of an RTK device significantly improved the accuracy by precisely georeferencing the capture. Deviations were minimal, ranging from just 1–2 cm, with corresponding point cloud density. For focused measurements on specific vehicle parts or deformations, accuracy was comparable to traditional terrestrial scanners.
Tips for effective image capture and processing with Pix4D's forensic solution
- Pix4D Autotags/ GCPs/ Auto Tie Points: streamline measurements by automatically identifying and displaying points in PIX4Dcatch and significantly improve accuracy when the RTK coverage is not optimal. Any errors during point measurement can be corrected during processing, ensuring accurate and reliable results
- Closed loops: ensure image capture starts and ends at the same point for better alignment and reconstruction
- Post-processing in PIX4Dmatic is key: use PIX4Dmatic's dedicated processing template for PIX4Dcatch data to get accurate results in the most efficient way
- Document your scene: combine a project overview, measurements, and screenshots into a custom report with PIX4Dmatic for easy sharing. Create a video flythrough to provide a clear visual narrative of the forensic investigation.
- Merge aerial and terrestrial data: you can bring drone and PIX4Dcatch datasets into the same project by merging them with PIX4Dmatic, to get a more complete picture of the scene
Pix4D's forensic solution: tested, accurate, and viable for forensic crash scene analysis
The results of this study highlight a major shift in forensic accident reconstruction. Traditional methods required multiple specialized tools, trained personnel, and significant time on-site, forcing investigators to balance speed with precision. With Pix4D's forensic solution, the process is now faster, more accessible, and cost-effective while still meeting the accuracy standards needed for legal and investigative work.
Extensive testing confirmed that this workflow is not only efficient but also highly accurate, with deviations ranging from just 1–2 cm and point cloud density comparable to traditional terrestrial scanners. For detailed vehicle damage analysis, accuracy remained on par with existing methods while offering the added benefits of reduced costs and ease of use.
This study validates that PIX4D’s forensic solution is a reliable alternative, delivering fast, precise accident scene documentation with the added advantages of automation and scalability. Its ability to create detailed 3D reconstructions, even in challenging conditions, marks a significant improvement over traditional methods and a promising advancement for forensic investigations.
__ Access the full report: original research document is available here (in Czech). With an English translation here (please note the English version is a Google translation).
