B. Choosing Streets
Streets are chosen following the steps specified in Fig. 15.
First, the user’s location is mapped onto the information
layer to identify the streets linked to the user’s location.
Connectedness between forks in the street data is queried and
only the regional data elements directly linked to the user are
queried. To measure the direction of the streets linked to the
user, the coordinates of the edge immediately linked with the
user are used to find the direction of the street. Finally, the
azimuth value in the mobile device is obtained. A threshold
number, k, is selected to determine whether each street is
within the distance of k. Only the streets within the boundary
of k are chosen.