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Hi all,
Should I filter the .trc data (marker data) before doing any scaling or inverse kinematics? Does it improve the estimation of joint angle? Or OpenSim has internal filtering before performing inverse kinematics?

Thanks

Filtering is typically performed after inverse kinematics, because IK does not necessarily produce smooth trajectories which is a pre-requirement for dynamic analysis. However, filtering is not a bad idea before processing the data through scaling or IK.

Does that mean IK result is not that reliable from OpenSim? Or it just a small amount of noise.

Hello,

IK solves a specific problem (find best set of coordinates to match marker data at a specific time frame in least squares sense). That said, there's no guarantee of any level of continuity for the solution since continuity would be based on a longer time history rather than a specific time frame.

Hope this helps,
-Ayman