Car speed estimation based on cross-ratio using video data of car-mounted camera (black box)

This paper proposes several methods for using footages of car-mounted camera (car black box) to estimate the speed of the car with the camera, or the speed of other cars. This enables estimating car velocities directly from recorded footages without the need of specific physical locations of cars shown in the recorded material. To achieve this, this study collected 96 cases of black box footages and classified them for analysis based on various factors such as travel circumstances and directions. With these data, several case studies relating to speed estimation of camera-mounted car and other cars in recorded footage while the camera-mounted car is stationary, or moving, have been conducted. Additionally, a rough method for estimating the speed of other cars moving through a curvilinear path and its analysis results are described, for practical uses. Speed estimations made using cross-ratio were compared with the results of the traditional footage-analysis method and GPS calculation results for camera-mounted cars, proving its applicability.