A navigation method includes steps of: repeatedly emitting, by a wheel speed sensor, a pulse signal to a processor of a vehicle when the vehicle starts to travel from a start point of a route of a map; in response to receipt of a preset number of the pulse signals transmitting, by the processor, the preset number of the pulse signals to a portable device; calculating, by the portable device, a current position of the vehicle on the map based on a distance associated with the preset number of the pulse signals; and transmitting, by the portable device, data of the map having the current position to the processor so as to display the same.