2_networkdm

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Department of Geography and UrbanStudies, Temple University

GUS 0265/0465Applications in GIS/GeographicData Analysis

Lecture 3: Net or! Data "odels



#epresenting and $naly%ing Net or!s in G&S

Net or!: a system of linear featuresconnected at intersections and interchanges

$ net or! is composed of a set of nodes anda set of spanning directed lin!s'

(ach lin! is represented by an ordered pairof nodes (i,j).



$n ()ample Net or!



()amples ofNet or!s



Node*Node $d+acency "atri)

The ro s and columns in the matri)correspond to the nodes on the net or!'

$ non*%ero element in the i th ro and j thcolumn in the matri) represents the numericalvalue associated ith lin! (i, j)'

$ %ero element in the matri) in the ith ro and +th column in the matri) indicates that there e)istsno lin! going from node i to node j '



Node*Node $d+acency "atri)

- . / - - -- - - 0 3 -

1 - - 2 - 1

- - - 4 -

- / - - - -

- - 0 - - -



5or ard Star #epresentation

Lin!s are numbered in the follo ing order:

5irst lin!s emanating from node 6 are numbered,then those from node 4, and so forth'

Lin!s emanating from the same node are numberedin an arbitrary fashion'

7nce this list of ordered lin!s is obtained, dataassociated ith the lin!s are stored in single arraysse8uentially'



Lin!No'

Starting*node

(nding*node

lin!*length

6 6 4 .

4 6 3 /

3 4 . 0. 4 / 3

/ 3 6 1

1 3 . 2

2 3 1 10 . / 4

. 6

6- / 4 /

66 1 3 0





9orresponding node (lement value

6 6

4 33 /

. 0

/ 6-

1 66

lin!No'

Starting*node

(nding*node

lin!*length

6 6 4 .

4 6 3 /

3 4 . 0. 4 / 3

/ 3 6 1

1 3 . 2

2 3 1 1

0 . / 4

. 6

6- / 4 /

66 1 3 0

Node ointer Table



#everse Star #epresentation

5or ard star representation facilitatesaccessing lin!s by beginning nodes

#everse star representation facilitatesaccessing lin!s by ending nodes

&ncoming lin!s at each node arenumbered se8uentially




lin!No'

Starting*node

(nding*node

lin!*length

6 3 6 1

4 . 6

3 6 4 .. / 4 /

/ 6 3 /

1 1 3 0

2 4 . 0

0 3 . 2

. / 4

6- 4 / 3

66 3 1 1




Node ointer Tablelin!No'

Starting*node

(nding*node

lin!*length

6 3 6 1

4 . 6

3 6 4 .. / 4 /

/ 6 3 /

1 1 3 0

2 4 . 0

0 3 . 2

. / 4

6- 4 / 3

66 3 1 1

9orresponding node (lement value

6 6

4 3

3 /

. 2

/

1 66



5or ard and #everse Star #epresentation



Net or!#epresentation

in $rc&nfo

6' 9omposed of (dgesand ;unctions

4' Geometric Net or!stores coordinates

3' Logical Net or!stores connectivity



Net or! #epresentation in $rc&nfoSolver: a program to perform net or! analysis

Trace: a solver that traces along a net or!

Net5lag: a location on a net or!

<eights: eighting travel along an edge

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