In motion capture applications using electromagnetic tracking systems the process of anatomical calibration associates the technical frames of sensors attached to the skin with the human anatomy. Joint centers and axes are determined relative to these frames. A change of orientation of the sensor relative to the skin renders this calibration faulty. is sensitivity regarding sensor displacement can turn out to be a serious problem with movement recordings of several minutes duration. We propose the "dislocation distance" as a novel method to quantify sensor displacement and to detect gradual and sudden changes of sensor orientation. Furthermore a method to de ne a so called xed technical frame is proposed as a robust reference frame which can adapt to a new sensor orientation on the skin. e proposed methods are applied to quantify the effects of sensor displacement of 120 upper and lower limb movement recordings of newborns revealing the need for a method to compensate for sensor displacement. e reliability of the xed technical frame is quanti ed and it is shown that trend and dispersion of the dislocation distance can be significantly reduced. A working example illustrates the consequences of sensor displacement on derived angle time series and how they are avoided using the xed technical frame.
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