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 14-4 Network components Composed of edges and junctions edges junctions
Copyright © 2006 by Maribeth H. Price 14-5 Network structure Geometric network is composed of feature classes Logical network consists of tables describing network relationships
Copyright © 2006 by Maribeth H. Price 14-6 Types of networks Transportation Networks Material moves as it wills Utility Networks Material flow dictated by network geometry and sources/sinks
Copyright © 2006 by Maribeth H. Price 14-7 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 14-8 Network tracing Tracing solvers used to find solutions to network problems
Copyright © 2006 by Maribeth H. Price 14-9 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 Network Utility Analyst toolbar Establish flowSolve
Copyright © 2006 by Maribeth H. Price Finding paths Place flags and barriers Solve Path with fewest edgesPath with construction Default cost is number of edges traversed
Copyright © 2006 by Maribeth H. Price 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 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 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 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 Finding loops Used to find places with indeterminate flow Primarily used for utility networks Flag Flow Loop
Copyright © 2006 by Maribeth H. Price 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 Tracing with accumulation Uses default cost (edges) or set weights Returns total cost associated with found trace
Copyright © 2006 by Maribeth H. Price 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 Advanced analysis Avoid certain features when tracing Trace only on unselected features to avoid certain streets
Copyright © 2006 by Maribeth H. Price Advanced analysis Return selection Use statistics to find length of connected water lines
Copyright © 2006 by Maribeth H. Price 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 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 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 Building networks 1231 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 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 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