Tracking-based 3D human skeleton extraction from stereo video camera toward an on-site safety and ergonomic analysis

Purpose - As a means of data acquisition for the situation awareness, computer vision-based motioncapture technologies have increased the potential to observe and assess manual activities for theprevention of accidents and injuries in construction. This study thus aims to present a computationallyefficient and robust method of human motion data capture for the on-site motion sensing and analysis. Design/methodology/approach - This study investigated a tracking approach to threedimensional(3D) human skeleton extraction from stereo video streams. Instead of detecting body jointson each image, the proposed method tracks locations of the body joints over all the successive frames bylearning from the initialized body posture. The corresponding body joints to the ones tracked are thenidentified and matched on the image sequences from the other lens and reconstructed in a 3D spacethrough triangulation to build 3D skeleton models. For validation, a lab test is conducted to evaluate theaccuracy and working ranges of the proposed method, respectively. Findings - Results of the test reveal that the tracking approach produces accurate outcomes at a distance, withnearly real-time computational processing, and can be potentially used for site data collection. Thus, the proposedapproach has a potential for various field analyses for construction workers' safety and ergonomics. Originality/value - Recently, motion capture technologies have rapidly been developed and studiedin construction. However, existing sensing technologies are not yet readily applicable to constructionenvironments. This study explores two smartphones as stereo cameras as a potentially suitable meansof data collection in construction for the less operational constrains (e.g. no on-body sensor required, lesssensitivity to sunlight, and flexible ranges of operations).