In an incident on a rainy night, an individual was carrying a food order to the driver-side of their parked car when a passing vehicle drove by and struck the individual, catapulting their dinner and tempered window glass across the sidewalk and building. One nearby security camera recorded the pre-impact approach of the striking vehicle, while another adjacent security camera recorded its post impact trajectory. It was observed that the passing vehicle’s tire marks were momentarily identifiable on the wet roadway. The visible tire marks were plotted on the roadway as part of the #photogrammetry process of matching the surveillance camera position and orientation to the to-scale 3D laser scan data of the site. While 3D tracking alone can produce highly accurate results, evidence such as the tire markings help refine and validate the accuracy of the 3D tracking of the impacting vehicle in the 3D collision reconstruction analysis.

Laurence R. Penn, CFVT, Senior Forensic Animation / Video Specialist with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-3020.

DJS Associates, Inc. – https://forensicDJS.com

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DJS was tasked with creating an animation depicting a tragic incident that unfolded in August of 2021. The incident involved the shooting of an 8-year-old girl, resulting from law enforcement’s response to gunfire at the conclusion of a high school football game. The animation project encompassed various components, including a laser-scanned 3D environment, to-scale representations of vehicles and people, the portrayal of a densely populated area, simulated gunshots, and the incorporation of sound effects.


To read more on this case, visit https://forensicdjs.com/3d-animation-bullet-trajectory-through-a-crowd/


Hugh Borbidge, BSME, Director of Engineering Animations with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

#engineering #investigation #3danimation #shooting

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To better understand the cause of a sports injury, reverse projection photogrammetry analysis was used to establish the movements of two football players through space and time. Utilizing video footage capturing the game from two separate camera angles, the players’ movements were reconstructed with to-scale 3D models relative to a scaled 3D model of the football field. The two angles of footage allowed for tracking movement that may have been obscured in one camera’s view by the bystanders seen along the sideline in the foreground of both videos.

The resulting 3D analysis provides an additional 360-degree examination of the players’ relative positions and the dynamics of their physical interaction. After establishing the precise movements of the players, further forensic analysis of the incident could be conducted by biomechanical engineers to evaluate the cause of injury. The combination of video footage and 3D analysis also serves as a dynamic demonstrative tool to bolster and/or illustrate the engineer’s analysis.

Created by Laurence R. Penn, CVFT, Senior Forensic Animation/Video Specialist with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

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Our Engineering Animations team at DJS Associates, Inc., followed methodical steps to accurately reconstruct the events that lead to an accident between an 18-wheeler and the red sedan depicted in this animation. Reconstructing vehicle collisions can help answer questions such as: Who was to blame – The driver of the tractor trailer, or the driver of the passenger car, or neither? Was the layout of the roadway to blame?

Working backwards from the points of rest allows us to piece together what happened and produce a visual reconstruction with animation technology. While recreating the environment using animation software, our engineers will reference photographs, visual markers and measurements collected on-site by our DJS 24/7 Rapid Response Team and Field Crew.

In this case, expert analysis concluded that the geometry of the roadway did not allow the tractor trailer to maneuver itself through the circle without the trailer encroaching into the right-hand lane. However, the following passenger car had sufficient time to perceive, react and slow down to avoid impacting the trailer.

Our collision reconstruction animations often include multiple perspectives to further demonstrate the vehicles’ paths leading up to the point of collision. By applying laws of physics and using measurements to ensure consistency, our engineers are able to accurately animate a single event from additional angles.

Hugh Borbidge, BSME, Director of Engineering Animations with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

https://forensicdjs.com/engineering-animation-accident-of-18-wheeler-and-red-sedan/

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To establish the position of vehicles in space and time, two-dimensional features captured in surveillance video are reprojected to their three-dimensional locations using high density laser scan data. While surveillance cameras are typically locked in position and rotation, a single frame can be used to calculate the camera’s position relative to the to-scale laser scan data of the environment it recorded.



Accurate photogrammetry requires rectilinear images, so part of the analysis process is to remove or correct any lens distortion present in the video. Lens distortion is common with surveillance cameras and results from spatially compressing a wide field of view to the constraints of standard video resolutions. With the lens distortion corrected and the camera position calculated, features on the vehicles are tracked in two-dimensions for multiple frames and correlated, to-scale, to their three-dimensional positions using laser scan data of the vehicles.




Laurence R. Penn, CFVT, Senior Forensic Animation/Video Specialist
https://forensicdjs.com/videogrammetry-extracting-temporal-spatial-data-for-3d-reconstruction/

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Surveillance videos often distort what they capture, making the recorded events difficult to analyze with an untrained eye. Such distortions will make otherwise geometric straight lines and edges look unnaturally bowed or curved. These distortions are often created by the type of lens on the surveillance camera since light passing through can be squeezed from a wide field of view into the narrower restrictions of the video format and resolution supported by the recording equipment. Luckily, software is available to undistort, or correct, such deformations into an image that is rectilinear; lines are returned, to the best of its ability, to their correct, geometrically straight nature. This process is also an important stage for performing photogrammetry and videogrammetry analysis where measurements are extracted from image and video data.

Included for example, is a video of a multi-lane roadway where delineating individual lanes is hindered by strong distortion of a wide-angle lens. Using filters in video analysis software, the video is undistorted, and the lanes straightened into a rectilinear image. Colored lines are superimposed over the painted skip lines for each lane, providing visual assistance to observe the vehicles traveling along the roadway including those involved in a collision.

Laurence R. Penn, CFVT, Senior Forensic Animation/Video Specialist with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

DJS Associates, Inc: https://forensicdjs.com

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When a surveillance camera captured an incident involving a school bus and motorcycle, the forensic science of videogrammetry and three-dimensional accident reconstruction helped determine the speeds of the vehicles and sight lines of the operators leading up to the collision.

Multiple high-density LIDAR scans of the site were captured by DJS Associates field crew to provide millions of accurately measured points from which the frame-by-frame photogrammetry was performed. By correlating many features on the two-dimensional surveillance image to their to-scale positions in the LIDAR scan data, the position and orientation of the camera was recreated in three-dimensional space with a virtual camera.

Scans of the bus were also captured and provided measurement data for tracking and plotting its position in the 3D reconstruction. The motorcycle position was then plotted in the scene for every frame of the camera-matched surveillance video. Additional vehicles moving through the intersection at the time of the incident were also plotted within the videogrammetry analysis.

Virtual cameras were placed in the 3D analysis at the approximate height of the vehicle operator views in order to observe possible obstructions or behavior leading up to the impact. The roadway approaching the intersection follows a hill and as a result, the time and distance the motorcycle was positioned at the crest relevant to the sight line of the bus operator was calculated. High quality animated renderings were produced from the accident reconstruction analysis to convey forensic engineer opinions.

Laurence R. Penn, CFVT, Senior Forensic Animation / Video Specialist with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-3020.

DJS Associates, Inc. – https://forensicDJS.com

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When a fatal collision occurred between a motorcycle and SUV at a city intersection, we were asked whether obstructed sight lines may have contributed to the incident.

Two surveillance videos which captured the events leading up to the collision were obtained and provided the foundation for the photogrammetry analysis within the accident reconstruction. From the video, it can be observed that there were several vehicles parked at/near the intersection. A box-truck parked near a crosswalk, the vehicle of interest for this case, was scrutinized as a possible obstruction to the approaching motorcycle and SUV operators.

The two videos were synchronized, and the camera locations were established by correlating multiple points on the 2D image plane to their 3D positions in space measured by high density LIDAR scans of the site.

The trajectories of the motorcycle and SUV were also solved by matching points on the 2D image frames to 3D scale models of the vehicles. The stationary vehicles parked along the roadway including the box truck were also analyzed and accurately placed within the scene. With 3D cameras placed at both operators’ positions, simulating their approaching views of the intersections, it was concluded that the presence of the box truck did not further impede the line of sight which already existed from the surrounding vehicles at the intersection.

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Laurence Penn, CFVT and Hugh Borbidge, BSME, Animation Consultants with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

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When a tree fell on a roadway, injuring a passer-by, DJS was tasked with analyzing the evidence to provide opinions on the measurements of the tree and extent of its canopy, including proximity to utility lines, prior to the incident.

A video from the scene and photographs of the property were provided for analysis. A scan of the site was performed by DJS field investigators, capturing high density LIDAR measurements. Using LIDAR assisted photogrammetry of the images and data provided from an arborist report, the position and angle of the tree were modeled in 3D. Major branches visible in the photos were also modeled to establish a canopy radius. 

https://forensicdjs.com

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