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uncertainty in the values of any kinematic variable depends on the error in the 3D coordinates that is propagated in any computed value determined from their combination. The propagated error can be minimized by maximizing the accuracy and precision of the OSS. The accuracy of the 3D coordinates depends on the digitizing procedure and the reconstruction technique, whereas precision depends on the digitizing procedure (Challis, 2008). A âGage Linearity and Biasâ test was performed to determine the accuracy of the measurement system throughout the expected range of the measurements, and a R&R study to determine systemâs precision. B.4.2. Procedure By placing the cameras on high tripods it was able to capture the surrounding area of the participants ensuring good visibility of the tracking markers, since handling box, adjustable platforms, other equipments, etc., could obstruct the cameraâs view of the markers. By increasing the angle between the cameras the captured reflections are also diminished. The appropiate set-up of the cameras minimize the dead space in each cameraâs field of view and maximize systemâs spatial resolution. Spatial resolution is affected by the capture volume and by camera position in relation to the capture volume. For an 2.0Ã2.0Ã2.0 m3 measurement volume, the diameter of the passive marker needs to cover about 1 200 of the field of view, i.e.,âfor a field of view of 2 m the marker diameter needs to be around 10 mm. In the current study the reflective markers of 20 mm diameter was used. Inter-marker distance measurement test was performed where four reflective markers attached on a bar on known positions and placed at eight different positions throught the established measurement volume and were recorded for 20 sec at sampling rate of 60 Hz. The motion analysis system was calibrated once at the beginning of the procedure. The 3D coordinates data were introduced to the Visual3D (C-Motion) software. The mean value of each sample was computed. Then, the distance between the markers was computed from their means value coordinate. B.4.3. Statistical Analysis The Grubbsâ test was used to check for outliers. A regression line was fitted on the bias against the reference values and statistics for the linearity and accuracy of the measurement system computed. It is assumed that biases are corrected by the calibration procedure, therefore, only the uncertainties of the correction are presented. The range over which the measurements varies due to normal variation computed by the R&R study. To determine the repeatability of the measurement system a R&R study carried on. The Minitab 17 statistical software was used for the analysis. B.4.4. Results Reports The precision of the measurement system was of 0.0012108 mm. The maximum absolute value of the bias, the linearity value, and the repeatability standard deviation were used for calculating the expanded uncertainty of the measurement system. Due to the anisotropic distribution of the error in the measurement volume, the final measurements took place at the centre of the measurement volume where the error was minimized. Due to the sensitivity of the error to the calibration 157