Entity Matching across Stereo Cameras for Tracking Construction Workers

Abstract

While GPS and RFID are dominantly used for tracking construction equipment and materials, 3D vision-based tracking that employs stereo-vision system has been also proposed as an alternative to efficiently track construction resources operating in a congested site. The 3D vision-based tracking requires an entity to be tracked in both cameras of the stereovision system so that two of 2D pixel coordinates are generated for each entity. Its 3D coordinate can be calculated by triangulating two projection rays that go through the 2D pixel coordinates. In order to track multiple entities of the same type simultaneously, the triangulation requires an additional process to match entities across the two camera views. This paper proposes an efficient method of entity matching for tracking construction workers. The method is mainly based on epipolar geometry which represents the geometric relation between two camera views. Two additional strategies - distance ratio thresholding and frame grouping - are introduced to reject false matchings and to ultimately increase precision of the 3D tracking. Experiment results demonstrate its suitability for automated entity matching for 3D vision-based tracking of construction workers.