Augmented Reality Approach for Marker-based Posture Measurement on Smartphones

Area of Science:

• Biomedical Engineering
• Human-Computer Interaction
• Kinesiology

Background:

• Marker tracking is crucial for postural and range of motion (ROM) assessments across various fields.
• Existing real-time mobile applications for limb angle and body posture measurement are limited.

Purpose of the Study:

• To develop a novel augmented-reality (AR) based Android smartphone application for real-time postural and ROM measurements.
• To evaluate the accuracy and reliability of the developed application.

Main Methods:

• Developed an Android application utilizing the AprilTag2 fiducial marker system.
• Tested the application using printed markers attached to a wall and a fixed smartphone.
• Recorded marker orientation and 2D position data from front and rear cameras under various smartphone placements.

Main Results:

• The application demonstrated high accuracy, with average angle errors less than 1 degree (e.g., back camera: 0.29°, front camera: 0.33°).
• Average distance measurement errors were less than 4 mm (e.g., back camera: 1.8 mm, front camera: 2.5 mm).
• Measurements remained valid and reliable across different smartphone positions and camera orientations.

Conclusions:

• The developed AR smartphone application provides valid and reliable measurements for angles and distances.
• This tool is a viable option for clinical range of motion and posture assessments.
• The application addresses the need for a real-time, accessible mobile solution for biomechanical analysis.