Fall 2006CS4455 Prototyping Maribeth Gandy [email protected] Jeff Wilson [email protected].
Copyright © 2006 by Maribeth H. Price 14-1 Chapter 14 Analyzing Networks.
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Transcript of Copyright © 2006 by Maribeth H. Price 14-1 Chapter 14 Analyzing Networks.
Copyright © 2006 by Maribeth H. Price
14-1
Chapter 14
Analyzing Networks
Copyright © 2006 by Maribeth H. Price
14-2
Outline
• Learning the function and terminology of simple networks
• Understanding different types of networks
• Performing tracing analysis on networks
• Understanding how networks are constructed
Copyright © 2006 by Maribeth H. Price
14-3
Geometric networks
• Built inside a feature dataset
• May have many participating feature classes
• Requires ArcEditor or ArcInfo to build
Copyright © 2006 by Maribeth H. Price
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Network components
• Composed of edges and junctions
edges
junctions
Copyright © 2006 by Maribeth H. Price
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Network structure
Geometric network is composed of feature classes
Logical network consists of tables describing network relationships
Copyright © 2006 by Maribeth H. Price
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Types of networks
Transportation NetworksMaterial moves as it wills
Utility NetworksMaterial flow dictated by network geometry and sources/sinks
Copyright © 2006 by Maribeth H. Price
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Network problems
• Transportation– What is the best path to
travel to sixteen delivery locations?
– What is the likely service area of a fire station based on travel time?
– What is the shortest path from point A to point B?
– What is the shortest path which avoids narrow streets?
• Utility networks– If a valve fails, which
customers will be affected?
– If I have to close this pipe for repairs, can I reroute water through another path to minimize service disruption?
– How will contamination at one location propagate through the network?
– Which sewer lines serve only residential customers?
Copyright © 2006 by Maribeth H. Price
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Network tracing
• Tracing solvers used to find solutions to network problems
Copyright © 2006 by Maribeth H. Price
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Flags and barriers
• Flags indicate points of interest (start, end, stops)
• Barriers stop flow through a feature
• Types should match when solving a problem
Junction flag
Junction barrier
Edge barrier
Edge flag
Copyright © 2006 by Maribeth H. Price
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Network Utility Analyst toolbar
Establish flow Solve
Copyright © 2006 by Maribeth H. Price
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Finding paths
• Place flags and barriers
• Solve
Path with fewest edges Path with construction
Default cost is number of edges traversed
Copyright © 2006 by Maribeth H. Price
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Finding shortest paths
• Use weights to override default cost
Find shortest path with distance weight
Shortest path with three stops Visited in order that
flags are placed
Copyright © 2006 by Maribeth H. Price
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Setting weights
• Analysis options
• Set for junctions or edges
• Edge weights have direction
• Usually need both directions
Possible weights: Distance, travel time, wait at stop lights, voltage or pressure drops, etc.
Copyright © 2006 by Maribeth H. Price
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Viewing flow directions
• Flow must be established for utility networks
• Flow direction symbols can be viewed and changed
• Set view scale to hide arrows at smaller scales
Copyright © 2006 by Maribeth H. Price
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Finding connected
• Find features connected to or disconnected from the flagged feature
Water lines supplied by an intake gallery
Copyright © 2006 by Maribeth H. Price
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Finding loops
• Used to find places with indeterminate flow
• Primarily used for utility networks
Flag
FlowLoop
Copyright © 2006 by Maribeth H. Price
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Directional tracing
• Find Upstream– Trace the flow from a
feature to its source
• Trace Downstream– Find the area
disrupted by a line break
Copyright © 2006 by Maribeth H. Price
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Tracing with accumulation
• Uses default cost (edges) or set weights
• Returns total cost associated with found trace
Copyright © 2006 by Maribeth H. Price
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Find Common Ancestors
• Finds common source for a set of flags
• Use to locate possible line break from a set of service calls
Probable break
Copyright © 2006 by Maribeth H. Price
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Advanced analysis
• Avoid certain features when tracing
• Trace only on unselected features to avoid certain streets
Copyright © 2006 by Maribeth H. Price
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Advanced analysis
• Return selection
• Use statistics to find length of connected water lines
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Network analysis options
• Tracing on selected or unselected features
• Inclusion of features with indeterminate flow
• Flag/barrier snapping
General options
Copyright © 2006 by Maribeth H. Price
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Results options
• Return result as drawing or as a selection
• All features or those stopping trace
• Return edges, junctions or both
Copyright © 2006 by Maribeth H. Price
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Weight filters
• Use to exclude certain weights from analysis– Screen out short
stop sign waits from longer traffice light waits
Copyright © 2006 by Maribeth H. Price
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Building networks
1 2 3 1
Simple edges—Edges may have junctions only on their endpoints
Complex edges—Edges may have junctions between their endpoints
Useful for query and management, such as a water main with many laterals
Copyright © 2006 by Maribeth H. Price
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How to build a network
• Ensure network features are topologically valid and inside a feature dataset
• Create new network for the feature dataset– Specify network layer– Simple or complex edges– Assign weights
Requires an ArcEditor or ArcInfo license.
To build a road network using your textbook data, see “Building a simple network” in the Skills Reference section.
Copyright © 2006 by Maribeth H. Price
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Tools for managing networks
• Domains and subtypes– Used to establish network attribute codes
• Pipes can only be 3-in, 6-in, or 12-in• Default sizes and flow rates for different types
• Connectivity rules– Define which features can connect to each
other and how• T-valve must connect to three pipes• 6-in line must connect to 3-in line through a
coupler