D. Data Search for information Layer
To provide regional data elements that are readily
accessible on the user’s path, the user’s location and
regional data elements are mapped onto the streets in the
information layer. Only the data pertaining to the user’s path
is queried. Data search for the information layer goes
through three stages of user location mapping, regional data
element mapping, and querying only the relevant data to the
user’s path.
1) User Location Mapping
To check how the streets in the user’s vicinity are
connected, the location of the user is first mapped onto the
information layer. For mapping, a distance, called , is
determined so that at least one fork is included in the map.
The forks are then put in a list. The distances between the
user and the forks are calculated and the closest fork is
identified. Fig. 11 shows an example in which the user’s
location (real_u) is mapped onto the closest fork (v4).