Are Action Sport Cameras Accurate Enough for 3D Motion Analysis? A Comparison With a Commercial Motion Capture System

Abstract

The aim of this study was to assess the precision and accuracy of an Action Sport Camera (ASC) system (4 GoPro Hero3+ Black) by comparison with a commercial motion capture (MOCAP) system (4 ViconMX40). Both systems were calibrated using the MOCAP protocol and the 3D markers coordinates of a T-shaped tool were reconstructed, concurrently. The 3D precision was evaluated by the differences in the reconstructed position using a Bland-Altman test, while accuracy was assessed by a rigid bar test (Wilcoxon rank sum). To examine the accuracy of the ASC in respect to the knee flexion angles, a jump and gait task were also examined using one subject (Wilcoxon rank sum). The ASC system provided a maximum error of 2.47 mm, about 10 times higher than the MOCAP (0.21 mm). The reconstructed knee flexion angles were highly correlated (r²>0.99) and showed no significant differences between systems (<2.5°; p>0.05). As expected, the MOCAP obtained better 3D precision and accuracy. However, we show such differences have little practical effect on reconstructed 3D kinematics.

Keywords: Accuracy; Precision; System Comparison.