自行车测速：主要是根据自行车行走时车轮转动的圈数，再与车轮周长相乘，得到行车路程，测出行车路程中所用的时间，即可得到车速。-bike speed：When walking was based largely on bicycle wheel rotation lap, again with wheel circumference multiplication, get the driving distance is measured in driving distance, of the amount of time, can get the speed limit.