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Stationary and Moving Camera Video Analysis Compared to Known Reference System
Abstract:
Video recordings of vehicular collisions have become widely available to the accident reconstructionist and can play a vital role in determining the locations and speeds of the subject vehicles involved in a collision. However, due to varying video resolutions, framerate, lens distortion, motion blur, and camera movement, errors in video analysis can occur. To understand the total error inherent to video analysis, this study presents analysis of videos from different video systems, the limitations in the analysis, and a comparison of video analysis speeds to reference datasets. The factors that influenced variance included resolution, lens correction, shutter speed, and framerate. The video systems analyzed included three moving cameras and two stationary units.
In the present study, a mock collision scenario in which a target vehicle approached a recording vehicle head-on, was staged to emulate an actual event captured on video. The target vehicle’s speed was analyzed using the captured videos. The video analysis results were then compared to the speeds obtained from the target vehicle’s wheel speed sensors via a VBOX system connected to the vehicle’s Controlled Area Network (CAN), and VBOX GPS position data.
The videos were recorded from two locations. Location 1 was at the top corner of a business complex. This location was equipped with two video cameras: a GoPro HERO5 and a Sony α6400 mirrorless camera. Location 2 was within the recording vehicle itself. This location was equipped with three video systems: a 2018 Tesla Model 3 Dashcam video camera system, a generic dashboard video system with a low framerate, and a Blackmagic Design camera. Videos were captured as the recording vehicle moved towards the target vehicle; the camera’s location and angle relative to the target were constantly changing.
Errors in the determined speeds were quantified based on comparison of the video analysis speeds to the reference datasets. The errors in speed were determined to be inversely correlated to the video resolution. Additionally, the analysis of the video footage from the stationary source yielded lower error than the analysis of the moving vehicle video for a given resolution and framerate.