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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
If users estimate degree of transportation networks in a 
certain interested region, they need base data such as high- 
resolution geo-spatial imagery containing spatial features on it. 
In this case, although two types of layers are also necessary, 
application scheme is a quite different from the former case 
dealing with district areas. 
  
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Figure 3. User input interface for computation of 
connectivity indices. ‘User draw’ button in step 
2 processes user-defined arbitrary boundary (A). 
B shows an arbitrary region, which can be 
determined by users, where nodes are 
automatically extracted in it. 
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A 
Alpha index Gamma index Shimbel index 
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A B c D A B c D A B c D 
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Figure 4. Actual application case using connectivity 
measures following by figure 3. 
In figure 4, the four sites of A, B, C, and D are arbitrarily 
chosen as test sites in the map display window. As known from 
results of indices values, the degree of connectivity of networks, 
alpha and gamma indices, does not show consistent pattern. 
Moreover, the degree of transportation concentration, as 
shimbel index, is somewhat distinguished in the B site. 
In this case, different patterns in alpha and gamma indices 
give practical meaning that both indices can be considered for 
the network structure analysis. The reason on low value in 
shimbel index in B site is that this are considered actual 
distances between nodes in a block. 
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2.2 Circuity and Level of Accessibility in the Matrix Form 
Similar to previous road-specific measures, transportation 
domain-specific demands with respect to practical applications 
and analysis scheme using spatial thematic information are 
increasing. Accordingly, GIS-based application program is 
implemented to perform spatial analysis in transportation 
geography with base road layer data. Among several 
approaches, quantitative estimation of circuity and accessibility, 
which can be extracted from nodes composed of the graph- 
typed network structure, in a arbitrary analysis zone or 
administrative boundary zone is possible. 
Circuity is a concept to represent the difference extent 
between actual nodes and fully connected nodes in the analysis 
zone. 
   
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Figure 5. (A) Example of Road network with 
distance, (B) Fully connected road 
graph network. 
Dx nn uou (4) 
C, == (ai. j) - eG, 
det [4 (/, 7) — e(i, j)] 
i=l 
where C; = circuity value at the ith node in a geven graph 
n = number of nodes in the graph or zone 
d(i,j), e(i,j) = desired distance or weight value and 
actual one between ith and jth node 
While, accessibility matrix [A] in equation (5) can be used 
to find out extent of accessibility or connectivity between all 
nodes contained in the analysis zone, judging from inter- 
connecting status of the whole nodes. Input data of this program 
is not transportation database information based on 
transportation data model, but layer data, directly obtaining 
from digital map sets. It is thought that computation of circuity 
and accessibility can be used as kinds of spatial analysis 
functions for GIS applications in the transportation field. 
ds (5) 
FIGE 
[4]=[C']+[C*]+[C’] 
where C" can be obtained as below in case of figure 5,