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Title
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Fig. 1 An example of path finding
In this process, two kinds of relationships between spatial objects
will be used. One is the adjacency between road segments and the
Zoo (M), which are used to find the road segments around the
Zoo. The other is the connectivity of road segments in the road
network, which is used to calculate the shortest route between A
and P. As we describe in section 3, these relationships can be
represented as 'special' area topology, arc-node topology, and
node-arc topology in ITS application. “Special” area topology in
this definition is different from the traditional TRs. It records the
TRs between some area features and the around road segments
rather than the TRs between area features and all their boundaries.
Moreover, topological relationships in ITS application need to be
constructed fast and automatically. The traditional methods,
which are time-consuming and inefficient, cannot satisfy these
requirements. In a word, the traditional TRs haven't considered
the characteristics of ITS application and they don't suit for ITS
applications very well. Therefore, we should study the specific
topological relationships in ITS application and find out efficient
algorithm to build topological relationships fast and
automatically.
The rest of the paper is structured as below. In section 2, the
traditional methods for building topological relationships and the
limitation of such methods are introduced. The third and forth
section expounds the topologically structured data model and the
algorithm for building full topology. The experiments and
corresponding results are given in section 5. The sixth section is
the summary.
d Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004
2. TRADITIONAL METHODS FOR BUILDING
TOPOLOGY
It's well known that TRs can facilitate spatial query, error
detection, and produce valuable derived statistics for revealing
graph or surface properties (Mark, Egenhofer, 1995; Kimfung Liu,
Wenzhong Shi, 2003). In the past years, two key issue related to
TRs, which are topological data model and algorithm for building
topology, have been discussed widely. On the one hand, many
topological data models have been developed and applied, such as
DIME model of the US Census Bureau for the 1970 census,
POLYVRT structure used by the ODYSSEY system of Harvard
University, and ARC/INFO topological data model (Laurini
Robert, Thompson Derek, 1992). In these models, topological
relations are generally recorded and stored in a tabular format.
For example, ARC/INFO defines different feature attribute tables,
such as PAT, AAT, NAT, TAT, to describe TRs of different
features, namely polygon, line, point, node and annotation.
Generally speaking, these models are related to certain
application fields (Ayse Can, 1996; Michael J. Mineter, 2003;
Serafino Cicerone, Eliseo Clementini, 2003; S. Dowers, B. M.
Gittings and M. J. Mineter, 2000), that is, different application
has different topological data models. On the other hand,
traditional algorithms for building topology can be divided into
three kinds. The earliest method for creating topology tables
depends on manual edits during the process of digitizing (LI LIN,
1987). It often appears excessively labor consuming and tedious.
With the development of computer technology, researchers begin
to make a study of a half-automatic method. They proposed to
figure out topological relations from line intersection
computation, which release people from the heavy and dull job.
However, such methods cannot, by themselves, handle islands or
self-intersecting arcs (Gold et al., 1994). Subsequently, Gold
proposed an approach based on voronoi diagram to generate the
adjacency relationships between each atomic element of the map.
Although it also has the ability to extract the traditional
polygon-arc-node topology, it contains an excess of information
and its storage requirements almost several times larger than for
the previous methods (Gold et al, 1991, 1994). Moreover,
whichever method described above consider the boundaries of the
area features when building the polygon topology. If we adopted
such methods in ITS application, we would need another table
besides the traditional polygon-arc-node topology to represent the
relationship between road and area features because the
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