A stereo vision-based approach to marker-less motion capture for on-site kinematic modeling of construction worker tasks

Marker-less motion capture has been extensively studied in recent years as a means of evaluating productivity, safety, and workplace design for manual operations on-site. These technologies are ideal for circumstances in which traditional motion capture systems are ineffective due to the need for a laboratory setting and movement-inhibiting markers or sensors. However, many marker-less motion capture systems rely on RGB-D sensors that have limited range and susceptibility to interference from sunlight and ferromagnetic radiation, making them unsuitable for modeling worker actions on construction sites. To address this issue, we propose a marker-less motion capture approach utilizing optical images and depth data obtained from stereo vision cameras. Multiple camera lenses and triangulation algorithms generate depths maps similar to those produced by RGB-D sensors, while still utilizing an optical recording process unhindered by potentially harsh construction site conditions. These data are adapted for existing kinematic modeling systems (i.e. iPiMocap Studio) for 3-D pose estimation. The experiments show that the proposed approach can provide data precision comparable to that of RGB-D-based systems with fewer operational constraints; thus, motion data can be collected where previously developed methods fail due to environmental or maneuverability restrictions. With the proposed approach, kinematic modeling of human movements can be carried out on construction sites without inhibiting the mobility of the recorded subject.