Cheung Allen, Zhang Shaowu, Stricker Christian, Srinivasan Mandyam V
Centre of Excellence in Vision Science, Research School of Biological Sciences, Australian National University, Canberra, ACT, 2601, Australia.
Biol Cybern. 2007 Jul;97(1):47-61. doi: 10.1007/s00422-007-0158-0. Epub 2007 May 23.
In principle, there are two strategies for navigating a straight course. One is to use an external directional reference and continually reorienting with reference to it, while the other is to infer body rotations from internal sensory information only. We show here that, while the first strategy will enable an animal or mobile agent to move arbitrarily far away from its starting point, the second strategy will not do so, even after an infinite number of steps. Thus, an external directional reference-some form of compass-is indispensable for ensuring progress away from home. This limitation must place significant constraints on the evolution of biological navigation systems. Some specific examples are discussed. An important corollary arising from the analysis of compassless navigation is that the maximum expected displacement represents a robust measure of the straightness of a path.
原则上，有两种沿直线行进的策略。一种是使用外部方向参考并不断参照它重新定向，而另一种则仅从内部感官信息推断身体旋转。我们在此表明，虽然第一种策略能使动物或移动体从其起点任意远地移动，但第二种策略即使经过无限多步也做不到。因此，外部方向参考——某种形式的指南针——对于确保远离起点的行进是必不可少的。这种限制必然会对生物导航系统的进化施加重大约束。文中讨论了一些具体例子。对无指南针导航分析得出的一个重要推论是，最大预期位移代表了路径直线度的一种稳健度量。
