International Society of Biomechanics
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Rigid Body Position and Attitude Estimation

In 3-D kinematic analysis of movement, we typically track the motion of three or more markers on a rigid body segment. Here are various methods to extract a 3-D position vector and rotation (or attitude) matrix from marker coordinates.

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An Excel spreadsheet that converts Euler X-Y-Z rotation angles to the other 5 possible rotation sequences as well as to the tilt-twist angles. Instructions are included in the spreadsheet.

default Euler.xls (23 KB)

Ron Jacobs, Ton van den Bogert

A Matlab function using singular value decomposition. Includes references.

default Matlab function (1 KB)

Joe Sommer

FORTRAN subroutines and test data for finite helical axis (FHA) and instant screw axis (ISA).

document FORTRAN subroutines and test data (27 KB)

H.J. Woltring.

A Fortran subroutine, using the eigenvalue decomposition method described in: Veldpaus et al., J. Biomech. 21,45-54 (1988).

default disp3db.fortran (7 KB)