Forensic accident reconstruction with phone and drone data

We interviewed Corporal James Lantz from the Maryland State Police (MSP) Crash Team to understand how the MSP uses Pix4D solutions in their workflow, including their recent application of this method, which resulted in a successful prosecution. The Crash Team merges drone aerial captures with terrestrial 3D scans (drone and phone) in PIX4Dmatic for comprehensive scene documentation.

Final resting place and key evidence of case study collision, merged PIX4Dcatch and drone projects are marked with markers in PIX4Dmatic

What is accident reconstruction?

Accident reconstruction teams investigate collisions and incidents to determine exactly how they occurred. This is crucial for understanding the contributing factors, assigning responsibility, and informing legal proceedings and safety improvements.

For law enforcement, the aftermath of a crash presents a challenge: documenting evidence while minimizing disruption. Traditionally, this balance has been difficult to manage. Methods like hand-drawn diagrams and tape measures were time-consuming and often led to prolonged scene closures, causing significant impact to traffic flow and daily routines. While technologies like total stations and GPS brought improvements, the need for faster, more comprehensive scene mapping remains a concern.

This is where digital mapping solutions step in. Faced with pressure to clear scenes efficiently without compromising the integrity of evidence, we sought a solution that could reduce documentation time while maintaining accuracy and detail.

Who are the MPS Crash Team and what is its mission?

The Maryland State Police (MSP) Crash Team is a law enforcement agency with statewide jurisdiction, tackling life-threatening injury and fatality crashes. We are authorized to operate in some of the most restricted airspaces in the United States. With the emergence of drones, the speed of evidence mapping has dramatically increased.

When using traditional methods (total stations), we had an average scene mapping time of between 1.5 to 2 hours. With drone mapping, this time is now an average of only 20 minutes, saving about 1.5 hours in incident investigative time! We have mapped over 700 crash and crime scenes since our drone mapping program began.

“What stands out about Pix4D for us is its ease of use and the power to combine multiple data sources into a single project. That flexibility is critical for our crash investigations." - Corporal James Lantz, Maryland State Police, Crash Team

Drone mapping also provides a more realistic and accurate map of the scene instead of a traditional line diagram. In circumstances where drones cannot be used, we use traditional methods with GPS stations and PIX4Dcatch (the smartphone scanning application). We later document the scene with a drone and merge the projects together in PIX4Dmatic.

Can you tell us about a project where you successfully used this method?

Yes, we recently used this method in a case that resulted in the successful prosecution for vehicular manslaughter. It showcased the capability to merge aerial and terrestrial data sources for the reconstruction of an accident into one project. Despite data collection occurring over two separate days, the resulting model accurately represented the scene as if it were on the date of the crash.

Accident scene. The final rest was marked with spray paint to aid in identification for 3D scanning application PIX4Dcatch on a smartphone and the drone/ aerial capture

Ground control points were used to tie the GPS and drone project together (on the tarmac on the left, and in the 3D mesh in PIX4Dmatic on the right)

How did Pix4D help this case?

The Pix4D software suite allowed us to integrate traditional methods of evidence collection with nontraditional data sets. This meant we could combine information from older, established techniques (like GPS station points) with newer digital captures (such as drone images and PIX4Dcatch phone scans) into a single, unified project. This flexibility was crucial for creating a complete and accurate accident scene reconstruction, no matter how or when the individual pieces of evidence were gathered. It provided one central platform for all our data, simplifying the entire reconstruction process. (check this is correct)

Screenshot of the PIX4Dcatch terrestrial project on the top left. Screenshot of drone project on the top right (both processed in PIX4Dmatic). The merged drone and phone project bottom, merged in PIX4Dmatic, using common points easily identifiable in both projects

Did you face any challenges with the software?

Implementing new technology or equipment always involves a learning curve, requiring team members to undergo training and become familiar with the tools. In the beginning, many lessons were learnt from trial and error, such as learning what techniques provided the best results for the conditions present.

Most team members transitioned from a standard autonomous grid pattern with a nadir camera angle to a manual flight pattern with an oblique camera angle. This provided greater control of the data captured to minimize privacy concerns and to ensure maximum data coverage at the incident. Because of the increased coverage, this flight pattern also produced better results. The team members were able to see the impact that different flight styles had on their final products.

A closer look at the merged drone/phone project in PIX4Dmatic

Why did you choose PIX4Dmatic?

We chose PIX4Dmatic because it offered greater control over content and features in the final output compared to PIX4Dmapper. This was particularly important for a case like this, where the initial crash occurred during the daytime with weather conditions that prevented immediate drone flight. Even with these challenges, the entire process—including data capture, processing, and generating the final deliverable—was completed in approximately 8 hours.

Project Details

What is your workflow for the digital reconstruction of an accident?

The scene was mapped using a GPS station, with Ground Control Points to precisely connect it with the drone project. The area of impact and vehicle resting places were documented using the PIX4Dcatch application. When weather conditions improved, the scene was then mapped with a drone.

Pix4D's integrated tools for marking and labeling allowed for the creation of a complete final product within one program, ensuring all data contributed to a single, comprehensive reconstruction.

7 There were multiple cameras that captured the crash events. The camera locations were marked in the mesh using markers. The field of view was marked using polylines