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Collecting kinematic data on a ski track with optoelectronic stereophotogrammetry : a methodological study assessing the feasibility of bringing the biomechanics lab to the field / Jörg Spörri, Christian Schiefermüller, Erich Müller
VerfasserSpörri, Jörg ; Schiefermüller, Christian ; Müller, Erich In der Gemeinsamen Normdatei der DNB nachschlagen
Erschienen in
PLoS One, Lawrence, 2016,
DokumenttypAufsatz in einer Zeitschrift
URNurn:nbn:at:at-ubs:3-850 Persistent Identifier (URN)
DOI10.1371/journal. pone.0161757 
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Collecting kinematic data on a ski track with optoelectronic stereophotogrammetry [7.29 mb]
Zusammenfassung (Englisch)

In the laboratory, optoelectronic stereophotogrammetry is one of the most commonly used motion capture systems; particularly, when position- or orientation-related analyses of human movements are intended. However, for many applied research questions, field experiments are indispensable, and it is not a priori clear whether optoelectronic stereophotogrammetric systems can be expected to perform similarly to in-lab experiments. This study aimed to assess the instrumental errors of kinematic data collected on a ski track using optoelectronic stereophotogrammetry, and to investigate the magnitudes of additional skiing-specific errors and soft tissue/suit artifacts. During a field experiment, the kinematic data of different static and dynamic tasks were captured by the use of 24 infrared-cameras. The distances between three passive markers attached to a rigid bar were stereophotogrammetrically reconstructed and, subsequently, were compared to the manufacturer-specified exact values. While at rest or skiing at low speed, the optoelectronic stereophotogrammetric systems accuracy and precision for determining inter-marker distances were found to be comparable to those known for in-lab experiments (< 1 mm). However, when measuring a skiers kinematics under “typical” skiing conditions (i.e., high speeds, inclined/angulated postures and moderate snow spraying), additional errors were found to occur for distances between equipment-fixed markers (total measurement errors: 2.3 2.2 mm). Moreover, for distances between skin-fixed markers, such as the anterior hip markers, additional artifacts were observed (total measurement errors: 8.3 7.1 mm). In summary, these values can be considered sufficient for the detection of meaningful position- or orientation-related differences in alpine skiing. However, it must be emphasized that the use of optoelectronic stereophotogrammetry on a ski track is seriously constrained by limited practical usability, small-sized capture volumes and the occurrence of extensive snow spraying (which results in marker obscuration). The latter limitation possibly might be overcome by the use of more sophisticated cluster-based marker sets.

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