Error assessment of a three-dimensional underwater motion capture methodology

Area of Science:

• Biomechanics
• Human Kinematics
• Motion Analysis Technology

Background:

• Assessing human movement underwater using motion analysis technology presents unique challenges.
• Accurate measurement of human kinematics underwater is crucial for reliable data.
• Understanding system setup and calibration errors is vital for underwater motion capture.

Purpose of the Study:

• To assess the accuracy and measurement error across the entire domain of a submerged motion capture system.
• To quantify the impact of system calibration and domain selection on kinematic accuracy.
• To inform researchers about potential error sources in underwater motion analysis.

Main Methods:

• Utilized six Qualisys cameras to establish an underwater capture volume (6.9 × 2.1 × 2.1 m³).
• Conducted uncertainty trials to evaluate average error levels within the capture volume.
• Analyzed measurement error distribution, including identifying areas of low accuracy near domain borders.

Main Results:

• Average error levels were acceptable (±5 mm) in specific uncertainty trials.
• Excluding areas with low accuracy near domain borders reduced measurement error by up to 0.13 mm.
• Interpolated error indicated potential kinematic alteration by up to 13.80 mm, affecting over 50% of the kick cycle.

Conclusions:

• Investigating error levels across the entire motion capture domain is essential for ensuring reliable kinematic results.
• Recalibration may be necessary, or areas with high error should be identified to improve data accuracy.
• This study underscores the importance of domain-wide error assessment in large-volume underwater motion capture systems.