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