The gravity model explicitly relates flows between zones to interzonal impedance to travel.
The gravity model explicitly relates flows between zones to interzonal impedance to travel.
如果不能得到小区之间的距离，出行时间或者运输成本，这种方法就有困难。
The gravity model explicitly relates flows between zones to interzonal impedance to travel.
如果不能得到小区之间的距离，出行时间或者运输成本，这种方法就有困难。