Accuracy of three-dimensional linear and angular estimates obtained with the Ariel Performance Analysis System.

Computer-assisted video motion analysis is a method of evaluating human kinematics that offers promise both for research and for clinical application. This study determined the upper limits of accuracy and consistency of linear and angular measures obtained using the Ariel Performance Analysis System. Reference standards included a meter stick and a universal 360 degrees goniometer. Average mean error observed for reconstruction of absolute point estimates was found to be less than 3.5 mm. Mean error estimate for three-dimensional (3D) reconstruction of a linear standard was found to be 1.4 mm (SD 0.30). Average mean angular error observed for 3D reconstruction of goniometer settings 10 degrees to 170 degrees was found to be 0.26 degrees (mean SD 0.21). System users are cautioned that some increased error associated with software derivation of joint angles exists as angles approach 180 degrees, use of wide-angle lens accessories introduces a systematic field-dependent bias; and planar rotation introduces some (< 2 degrees) random error.