A method to minimise error in 2D-DLT reconstruction of non-planar markers filmed with a moving camera.

The research paper explores a novel technique that enhances the accuracy of the two-dimensional version of the Direct Linear Transformation (2D-DLT) when the marker is not exactly on the calibration plane. The improved 2D-DLT reduces errors significantly when measuring slip distances, which is beneficial for high-speed outdoor locomotion analyses using a moving camera.

Methodology

• The researchers established an experiment protocol that involved filming markers placed in a vertical line above, below, and in the centre of a horizontal calibration plane.
• The filming was conducted using a moving camera.

Findings

• The initial results show considerable errors (up to 64.5%) in the data for markers that did not reside in the calibration plane.
• However, the improved 2D-DLT method remarkably reduced these errors, aligning the calculated coordinates with the actual values, keeping the error rate below 0.55%.

Practical Application

• To test the practicality of the method, the research team used it to measure the slip distance in a real-world scenario.
• A marker was fixed on the hoof of a trotting horse on a calibrated track and filmed with a moving camera.
• In this instance, the correction effect constituted 6.6% of the overall slip distance.

Conclusion

• This research illustrates the potential of the corrective method in conjuction with the 2D-DLT transformation.
• It significantly improves the measurement accuracy of slip distances, especially in high-speed outdoor locomotion analyses using a moving camera.

The authors conclude that such a technique could revolutionize the way slip distances are measured and enhance the accuracy of such measurements, even in challenging conditions.