International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004
(1) Sketch map
Figure 6 the disposal of dangle ed
oe
A/Ay, — (A90) A (A90) A (Avi)
2-Ay/Ax, (A>) A(A>0) A (A < Axi)
2—-Ay/Ax, (Ay X 0) A (A70) A(Aa» — Ay) The algorithm has been tested in our experiment environment.
4+Ax/Ayı, (Ay « 0) A (A70) ^ (^a E—Ay) The development environment is Delphi 6.0 and MapX. The
4+A0/Au, (An <0) A (Ax <0) A (A X Ax) experiment data is the road network data within the second ring of
6—Ay/Ax, (Ay <0) (Au «0) (A > Ax) Beijing. And the experiment is completed in the personal
6— AWA, (A >0) A(An <0) A(Ap €x) computer that has PII CPU, 256M memory and Win2000 OS.
8+Ax/An, (An >0)A(Au <0)A(Au >—An)
(2) Formula
5. EXPERIMENTS
Qx y)-
Table 7 is the result in comparison with the traditional methods.
In the table, Ty; is the node-edge topology and Tr is the special
à area topology. And TM represents the traditional Methods; PM
Fig. 5 Qi Operators ;
represents the present methods. From the experiment result, we
know that when building the node-edge topology the time
When searching for the next edge in the clockwise based on the
efficiency of the present algorithm is similar with that of the
current edge, we at first compute the value of Qi operator of every
traditional one. But when building the area topology, the present
edge that is related to the end node of the current edge. Then sort
algorithm saves us much more time. Moreover, the constructed
them ascending. If Gi; is in the front of Qi; the edge whose Qi
? area topology is more appropriate to the ITS application.
operator values Qi; is the next edge of the one whose Qi operator
values Qi;.
Time Twx (S) Tax (S)
: Data TM PM TM PM
The disposal of Dangle Edge: Generally speaking, the dangle
id Edge:!104 ]" 0.9" 3" j"
nodes should be removed before building the polygon topology.
; : E Node..68
But in the road network, the dangle edge is permitted, such as the
; ee : Edgel 11,128 3" 2" 13" 4"
dead road. Therefore, while building the special area topology,
: re ae Node! 1736
we should dispose the dangle edges distinguishingly to ensure
: T Edge 112,485 12" 8" 125" 18"
that the search process continues. In our methods, we at first
‘ : Node/18768
judge whether the number of the edge related to the current node
is only one. If it is, the current edge is dangle edge. Change the Table 7 The Experiment Results
current node to the other node of the current edge and search
unceasingly. Fig. 6 describes the disposal process of dangle edge.
on . DISCUSSION AND CONCLUSION
The arrows identify the search direction. 6
The experiment indicates that the algorithm presented in the paper
has the following advantages. Firstly, the proposed topological
relationships, which are composed of edge-node topology,
node-edge topology and “special” area topology, are more
appropriate to ITS application because they consider the
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