The Principles of 3D Photogrammetry Systems Used in Human Motion Capture and Postural Assessment

There are many different systems capable of objectively measuring and analyzing various motion parameters and signals. The focus of this chapter is on describing the measurements of kinematic parameters, e.g. spatial position, velocity and acceleration. To this end we introduce a photogrammetric approach where spatial three-dimensional (3D) measurements are derived from 2D camera images. The principle how a camera models 3D world into 2D image is described with the camera model parameters, and the computation of parameters through the camera calibration[aut]Camera calibration procedure is presented. Since 3D kinematic systems[aut]3D kinematic systems operate on a stereo principle, it requires imaging of the scene with minimum of two cameras and their spatial relationship is given in the form of epipolar geometry. We further turn our focus to the usage of 3D kinematic systems3D kinematic systems which is frequently defined by certain measurement protocol, tailored to analyzing a specific movement. Several popular possibilities where 3D kinematic system is jointly used with other types of devices are pointed out. Additionally, an inverse dynamics[aut]Inverse dynamics approach is briefly described and explained, allowing a derivation of internal kinetic data (joint forces and torques) combining an output of a 3D kinematic system with inertial body segment parameters. At the very end, several topics related to the research challenges and the anticipated development of 3D reconstruction systems are presented.