三维跟踪扫描影像分析方法的实现与精度分析

三维影像分析是运动生物力学的重要研究手段之一,广泛地应用于运动技术分析和诊断中.三维跟踪扫描影像分析方法就是摄像机跟踪运动目标来记录运动的图像,并通过专门的图像解析系统解算得到运动目标空间实际三维坐标的方法.应用SIMI Motion的Pan/Tilt/Zoom功能来实现三维跟踪扫描录像分析,并对所得到的三维测量数据的精度进行评价和分析.研究结果表明,在相同的坐标参考系下,由全站仪和影像分析测量得到的24个点的三维空间绝对坐标的平均相差值为0.018±0.003 m,三维跟踪扫描影像测量的相对误差可以达到1.97%,这样的测量精度可满足运动技术分析的要求.介绍了实现三维跟踪扫描影像分析的全过程,对影响测量精度的因素进行了初步的分析,并提出了应采取的相应措施.     

Static versus dynamic kinematics in cyclists: A comparison of goniometer,inclinometer and 3D motion capture

Kinematic measurements conducted during bike set-ups utilise either static or dynamic measures. There is currently limited data on reliability of static and dynamic measures nor consensus on which is the optimal method. The aim of the study was to assess the difference between static and dynamic measures of the ankle, knee, hip, shoulder and elbow. Nineteen subjects performed three separate trials for a 10-min duration at a fixed workload (70% of peak power output). Static measures were taken with a standard goniometer (GM), an inclinometer (IM) and dynamic three-dimensional motion capture (3DMC) using an eight camera motion capture system. Static and dynamic joint angles were compared over the three trials to assess repeatability of the measurements and differences between static and dynamic values. There was a positive correlation between GM and IM measures for all joints. Only the knee, shoulder and elbow were positively correlated between GM and 3DMC, and IM and 3DMC. Although all three instruments were reliable, 3D motion analysis utilised different landmarks for most joints and produced different means. Changes in knee flexion angle from static to dynamic are attributable to changes in the positioning of the foot. Controlling for this factor, the differences are negated. It was demonstrated that 3DMC is not interchangeable with GM and IM, and it is recommended that 3DMC develop independent reference values for bicycle configuration.     

Accuracy of an UWB-based position tracking system used for time-motion analyses in game sports

Abstract

The main aim of this study was to determine the accuracy of the ultra-wideband (UWB)-based positioning system Ubisense, which is used for time-motion analysis in sports. Furthermore, some alternatives for positioning the system's transponders on the atheletes, as well as the accuracy depending on the location of measurement, were tested. Therefore, in a pre-study, some basic issues were examined (measurement assumptions and consistency and location of the system's transponder used for position detection), and position measurements at the borders and in the centre of a basketball field were performed. In the main study, 13 male basketball players (15.8 years ± 0.6; 187.9 height ± 3.4; 77.5 weight ± 3.7), equipped with a Ubisense transponder mounted on top of their heads, handled a trundle wheel during simulated match play. The players with the trundle wheel participated passively in the match by following one of the ten competing players. The distance measurements of the trundle wheel were used as reference values and compared to the Ubisense distance estimations. Best results were found with the measurements of a single mounted transponder on top of the athlete's heads. No differences were detectable in the accuracy between measurements in the centre and at the borders of the basketball field. The (Ubisense) system's difference to the (trundle wheel) reference was 3.45 ± 1.99%, resulting in 95% limits of agreement of ?0.46–7.35%. The study indicates the examined system's sufficient accuracy for time-motion analysis in basketball.