The validity of the Shadowbox™ magnetic and inertial tracking system for measuring soccer-specific movements
Raw data from the Shadowbox™ sensors was downloaded via USB interface and imported into MATLAB software for data processing. A quaternion-based extended Kalman filter was used to combine the raw sensor data to generate an estimate of the Shadowbox™ position, velocity and attitude using the methods of van der Merwe and Wan (2004) and Bachmann et al. (2001). Figure 2 illustrates a block diagram of the Kalman Filter procedure used to derive the displacement of the Shadowbox™. A Pearson product-moment correlation was then calculated
between the 3D displacement data for the Shadowbox™ and the Vicon MX™ for each action to determine the dependence between the two methods.