As a matter of fact, there is a critical difference between a pedestrian navigation
and a car navigation.
Since the human walking speed is considerably slower than a car, GPS is unable to accurately estimate
the walking path and hence the moving direction.
Furthermore, the GPS signal often can not reach between large buldings making it diffuclt to accurately
estimate the direction.
Even if the GPS can determine the position of the user, the directon of the user can not be
estimated by that alone or if the user is stationary.
So in a case where a user wants to know which way to go at a subway exit, this can not be realized by using a GPS alone.