Geography Reference
In-Depth Information
N1
Node
Vertex
From
node
To
node
Length
Arc
A1
1
1.358
1
3
N2
0.529
2
3
4
N3
A3
1.230
3
2
4
A2
4
5
7
0.665
N5
N4
5
4
7
2.335
N6
A5
6
4
8
0.991
A4
A7
A6
N7
7
6
8
1.204
N9
N8
8
7
9
0.674
A8
A9
A11
A10
9
7
10
0.797
N10
10
8
10
2.588
N12
11
8
11
0.728
A12
N11
A13
12
10
12
0.687
13
10
13
0.598
N13
Figure 2.3
Line topology representation. The prefi x 'N' refers to node and the prefi x 'A' to arc.
N1
A1
From
node
To
node
Left
polygon
Right
polygon
1
A4
Arc
2
A2
1
2
1
1
2
N2
2
3
1
2
3
A3
3
3
2
4
2
4
1
4
1
3
N3
3
5
5
3
4
3
6
4
5
5
3
7
6
5
4
5
8
6
2
1
4
9
4
6
1
5
A5
Record
Area
Perimeter
Polygon
A6
N4
1
4208522
8206.625
1
4
N5
2
391022.2
2931.427
2
3
1837280
5843.305
3
5
A7
A8
4
1552205
5846.086
4
A9
N6
5
428014.2
3045.462
5
Figure 2.4
Polygon topology representation. The polygon numbers are those without a prefi x.
The prefi x 'N' refers to node and the prefi x 'A' to arc.
start and end node (indicated with the prei x 'N' on the i gure) of each arc (given by
the prei x 'A' on the i gure) and the polygon that lies to the let and right of each arc
(given by numbers without a prei x). Note that the negative area for polygon 1 corre-
sponds to the area outside the edge of the region and it is the negative of the sum
of areas within the boundary (i.e. if you take the absolute value of this i rst area i gure,
this gives the total area within the outer edge). Additional tables with the same arc
identii ers can be added easily with a relational database structure. With a relational
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