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How Do You Test Dynamic Accuracy / Precision? Why Is It More Important Than Static Measurements?

Due to the complexity and many variables involved in motion capture systems, direct comparisons between different experimental methods are close to impossible, and results will vary with different test conditions.

It is important any measurement used reflects the typical use for an optical motion capture system, and in particular measures a moving (dynamic) object. Our standardized test results were obtained using the method described in ASTM E3064 (‘Standard Test Method for Evaluating the Performance of Optical Tracking Systems that Measure Six Degrees of Freedom (6DOF) Pose‘) which is highly reflective of a typical use case.

Below in an example, a separate test shows the difference simply between a measurement taken in a single capture, for an object that starts stationary, and then begins moving part way through the capture, with no other changes being introduced.

Measured Bar Length - Statis vs Dynamic Test
Single capture showing difference between measurement of a static and dynamic object

Mean (mm) Max Error (mm) Root Mean Squared Error (mm) Standard Deviation (mm)
Static Object 320.875 0.035 0.007 0.005
Dynamic Object 320.979 0.397 0.142 0.102

The introduction of movement to on object significantly increases the variability of the measurements being taken in the raw data.

This involves the measurement of an object comprising two clusters of passive markers (forming a rigid body at each end). The distance between them was measured to produce a reference measurement. This object was moved around an optical capture volume in a defined way, according to the standard ASTM E3064, and the two rigid bodies were tracked independently by the capture system and compared to an external fixed reference measurement.

Please contact Vicon ([email protected]) for further details or to request a white paper detailing the experimental methods used.