Fig. 2From: Finite helical axis for the analysis of joint kinematics: comparison of an electromagnetic and an optical motion capture systemCompensation of the position data error due to the distortion of the electromagnetic field. The top panels a, b show the original coordinates of the trajectories of the second Polhemus sensor during the different acquisitions in top and side view respectively. The bottom panels c, d show the same data after the application of the bidimensional function of the second order that minimizes the distortion in the z axisBack to article page