Biomedical Engineering Reference
In-Depth Information
4
Errors in Measurement
With regard to optoelectronic motion analysis systems,
based on passive markers, the sources of instrumental errors
and especially experimental errors (correct location of
anatomical landmarks and soft tissue artifacts) will be
described and quantified. With soft tissue artifacts being the
key problem to tackle, and still an open research topic,
the methods currently proposed to solve this problem will
also be presented in this chapter.
4.1. Instrumental errors
Instrumental errors are errors those result from the
reconstruction of the three-dimensional (3D) positions of
passive markers in the coordinate system of the laboratory,
which are due to the optoelectronic system itself. There
are two types of instrumental errors [CHI 05]: systematic
errors that depend on the validity of the model chosen to
define the cameras and the accuracy with which the
parameters of this model are identified during calibration of
this system, and random errors associated with the
calculation of the marker, i.e. when taking into account the
distortion in shape when the obturation velocity is not
