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Key Arc 8 additions to the network dialogue
• Review L&T Chapter 5 pages 175-183, 206-211• Zeiler Chapter 8• Aspects of ESRI network
– geometric network• the “actual” mapped thing consisting of features with
geographic aspects etc
– logical• network graph (L&T 176) showing relationships of
connectivity
– components
– edge and junction
Edges (basics)
• geometric manifestation– typically single geometric element
(polyline) connecting two nodes– members of feature class
• logical manifestation– pointers to geometric features
• possibly from many different feature classes
ID Geometry Attributes
Element ID Feature class ID Feature ID
ID Geometry Attributes
ID Geometry Attributes
Feature class 1
Feature class 2
Junctions (basics)
• geometric manifestation– point features
• same geographic locations as nodes that are ends of some (not all) linear features
• linear feature “end” nodes are NOT automatically junction features
• logical manifestation– intersections, ends of edges
– table of pointers to point features
ID Geometry Attributes
ID Geometry Attributes
ID Geometry Attributes
Point feature class 1
Point feature class 2
Element ID Feature class ID Feature ID
Features to logical elements
Water Main feature line class
Service Line feature line class
ID Geometry Attributes
ID Geometry Attributes
ID Geometry Attributes
ID Geometry Attributes
Service Tap (point) feature class
Meter feature (point) class
ID Fea class ID Fea ID
ID Fea class ID Fea ID
Junction Features
Edge Element
Junction Adj Jun Adj Edges
Connectivity
Junctions and edges
• There need not be any one-to-one relationship with a node in the geometric network and a junction in the logical one
• Appropriate nodes in a geometric network will need to be designated as junctions
Nodes
junctions
Simple vs complex edges
• A simple edge has a one to one correlation between the network feature and the logical network element Main 2
S 1
S2Me 1
Me 2
T 2T 1
Water Main feature line class
Service Line feature line class
ID Geometry Attributes
ID Geometry Attributes
ID Geometry Attributes
ID Geometry Attributes
Service Tap (point) feature class
Meter feature (point) class
Splitting simple edges• To manage as simple
features will need to break signal main into three features
Water Main feature line class
ID Geometry Attributes
ID Fea class ID Fea ID
Ma 1
Ma 2
Ma 3S 1
S2Me 1
Me 2
T 2T 1
Ma 1
Ma 2
Ma 3
ID Geometry AttributesS 1
S 2
Service Tap feature class
Edge elements
Splitting complex edges• To manage a complex edge the
single feature can have junctions placed along edge w/out actually breaking feature
Water Main feature line class
ID Geometry Attributes ID Fea class Fea Sub ID ID ID1 Main 1 12 Main 1 23 Main 1 34 Ser 1 15 Ser 2 1
Main 1
S 1
S2Me 1
Me 2
T 2T 1
Main 1
ID Geometry AttributesS 1
S 2
Service Tap feature class
Edge elements
Complex junctions
• Complex junctions reflect situations such as an electrical switch where the “inside” of the geometric feature actually has capabilities to “redirect” flows through network
• Geometry stays constant but network logical structure changes
• States of switch can be reflected in different logical network structures
Geometric
Network flows
• Flows are reflected in a flow column in the logical network
• Flows are defined as “with” or “against” the digitized direction of the element
ID Fea class Fea Sub Flow ID ID ID1 Main 1 1 Against2 Main 1 2 With3 Main 1 3 With4 Main 2 1 Against5 Main 2 2 With
Edge elements w/ flows
Overall direction of flow
Arrows reflect direction element was digitzedM1
M2M3
M4
M5
Source and sink• An individual node geometry may actually serve the role of a
source or a sink in the logical network– sources
• spring in river• water tank• water well• electrical generating station• house sewer outflow
– sinks• water meter on house• electrical meter • waste water treatment plant
• A column “Ancillary Role” is added to junction table in logical network– entries in column ‘source,” “sink” or blank
Weights
• In the current release of Arc 8 weights can be applied to both edge and junction features
• weights can be viewed as the cost (time etc.) to traverse an edge or junction.
• some limitations – apparently Arc 8 DOES NOT support turn tables
– nor does it support allocation applications
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