Witte T H, Wilson A M
Structure and Motion Lab, The Royal Veterinary College, Hawkshead Lane, Hatfield, Hertfordshire AL9 7TA, UK.
J Biomech. 2004 Dec;37(12):1891-8. doi: 10.1016/j.jbiomech.2004.02.031.
Accurate determination of speed is important in many studies of human and animal locomotion. Some global positioning system (GPS) receivers can data log instantaneous speed. The speed accuracy of these systems is, however, unclear with manufacturers reporting velocity accuracies of 0.1-0.2 ms(-1). This study set out to trial non-differential GPS as a means of determining speed under real-life conditions. A bicycle was ridden around a running track and a custom-made bicycle speedometer was calibrated. Additional experiments were performed around circular tracks of known circumference and along a straight road. Instantaneous speed was determined simultaneously by the custom speedometer and a data logging helmet-mounted GPS receiver. GPS speed was compared to speedometer speed. The effect on speed accuracy of satellite number; changing satellite geometry, achieved through shielding the GPS antenna; speed; horizontal dilution of precision and cyclist position on a straight or a bend, was evaluated. The relative contribution of each variable to overall speed accuracy was determined by ANOVA. The speed determined by the GPS receiver was within 0.2 ms(-1) of the true speed measured for 45% of the values with a further 19% lying within 0.4 ms(-1) (n = 5060). The accuracy of speed determination was preserved even when the positional data were degraded due to poor satellite number or geometry. GPS data loggers are therefore accurate for the determination of speed over-ground in biomechanical and energetic studies performed on relatively straight courses. Errors increase on circular paths, especially those with small radii of curvature, due to a tendency to underestimate speed.
在许多关于人类和动物运动的研究中，准确测定速度至关重要。一些全球定位系统（GPS）接收器可以记录瞬时速度数据。然而，这些系统的速度准确性尚不清楚，制造商报告的速度精度为0.1 - 0.2米/秒。本研究旨在试验非差分GPS作为在实际条件下测定速度的一种方法。骑着自行车在跑道上行驶，并对定制的自行车速度计进行校准。还在已知周长的圆形轨道和直道上进行了额外的实验。通过定制速度计和记录数据的头盔式GPS接收器同时测定瞬时速度。将GPS速度与速度计速度进行比较。评估了卫星数量、通过屏蔽GPS天线实现的卫星几何形状变化、速度、精度的水平稀释以及骑行者在直线或弯道上的位置对速度准确性的影响。通过方差分析确定每个变量对总体速度准确性的相对贡献。GPS接收器测定的速度在45%的值中与实测真实速度相差在0.2米/秒以内，另有19%的值相差在0.4米/秒以内（n = 5060）。即使由于卫星数量少或几何形状不佳导致位置数据质量下降，速度测定的准确性仍然得以保持。因此，在相对直的路线上进行的生物力学和能量学研究中，GPS数据记录器对于地面速度的测定是准确的。在圆形路径上，尤其是那些曲率半径小的路径上，由于存在低估速度的趋势，误差会增加。
