Databases Reference
In-Depth Information
Figure 18: Cost-first
method
Figure 20: Station and line names of circular and central
JR train lines
Figure 19: Intersection-first
method
passes the central part of Tokyo, the cost of candidate places are slightly modified
in such a way that one-third and two-third positions of a polygonal line has zero
cost. In this case, the intersection-first greedy algorithm performs better.
So far, we have dealt with the ELP problem for edge labels. In concluding this
subsection, we show a result for the GFLP problem for node and edge labels for
the train map with line names and station names. For point labels, four natural
candidate positions (NW, NE, SW, SE) of a point are considered. Since line names
have more freedom, the point labeling is put higher priority. Fig.20 is a result for
JR lines, circular line and central line, in Tokyo. For 47 out of 48 stations, together
with two line labels.
4
Finding Detours in ITS
For the car navigation system, the most typical query is a shortest-path query.
This query is very important in mobile computing environments based on GIS
5)
.
As dynamical traffic information newly becomes available such as ATIS and
VICS mentioned in the introduction, more sophisticated queries come to be
required. Also, the static geographical database of roads itself has grown up further,
and similarly in this respect advanced types of queries are necessary to realize a
