Polk John D, Psutka Sarah P, Demes Brigitte
Department of Anthropology, University of Illinois Urbana Champaign, 607 S. Mathews Ave., Urbana, IL 61801, USA.
J Hum Evol. 2005 Dec;49(6):665-79. doi: 10.1016/j.jhevol.2005.06.008. Epub 2005 Sep 15.
Quantitative analyses of animal motion are increasingly easy to conduct using simple video equipment and relatively inexpensive software packages. With careful use, such analytical tools have the potential to quantify differences in movement between individuals or species and to allow insights into the behavioral consequences of morphological differences between taxa. However, as with any other type of measurement, there are errors associated with kinematic measurements. Because normative kinematic data on human and nonhuman primate locomotion are used to model aspects of gait of fossil hominins, errors in the extant data influence the accuracy of fossil gait reconstructions. The principal goal of this paper is to illustrate the effect of camera speeds (frame rates) on kinematic measurement errors, and to demonstrate how these errors vary with subject size, movement velocity, and sample size. Kinematic data for human walking and running (240 Hz), as well as data for primate quadrupedal walking and running (180 Hz) were used as inputs for a simulation of the measurement errors associated with various linear and temporal kinematic variables. Measurement errors were shown to increase as camera speed, subject body size, and interval duration all decrease, and as movement velocity increases. These results have implications for the methods used to calculate subject velocity and suggest that using a moving marker to measure the linear displacements of the body is preferable to the use of a stationary marker. Finally, while slower camera speeds will always result in higher measurement errors than do faster camera speeds, this effect can be moderated to some extent by collecting sufficiently large samples of data.
利用简单的视频设备和相对便宜的软件包，对动物运动进行定量分析越来越容易。如果谨慎使用，这些分析工具有可能量化个体或物种之间运动的差异，并深入了解不同分类群之间形态差异的行为后果。然而，与任何其他类型的测量一样，运动学测量也存在误差。由于人类和非人类灵长类动物运动的标准运动学数据被用于模拟化石人类的步态特征，现存数据中的误差会影响化石步态重建的准确性。本文的主要目的是说明摄像机速度（帧率）对运动学测量误差的影响，并展示这些误差如何随研究对象的大小、运动速度和样本量而变化。人类行走和跑步的运动学数据（240赫兹），以及灵长类动物四足行走和跑步的数据（180赫兹）被用作输入，以模拟与各种线性和时间运动学变量相关的测量误差。结果表明，测量误差会随着摄像机速度、研究对象身体大小和时间间隔的减小以及运动速度的增加而增大。这些结果对计算研究对象速度的方法具有启示意义，并表明使用移动标记来测量身体的线性位移比使用固定标记更可取。最后，虽然较慢的摄像机速度总是会比较快的摄像机速度导致更高的测量误差，但通过收集足够大的数据样本，这种影响可以在一定程度上得到缓解。
