Network Analysis

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Network Analysis

• By Josh Bundick
• EVSC 468 Advanced GIS
• March 27, 2003

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Agenda

• Network Analysis What is it?
• What are the tools needed?
• What do the tools do?
• How can they help me?
• How do they work?
• Demos
• Conclusions

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What is a network?
Any system of interconnected linear features
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What is network analysis?

• Solving problems involving networks
• Goal is efficiency Saving time and money

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What tools are needed?

• Network data (connectivity is needed)
• Network analysis software A GIS!

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What part of the GIS do I use?

• Workstation Arc/Info Old School, command line
  - driven
• ArcView 3.x Network Analyst Extension - Menu
  driven and much more user friendly
• Currently, ArcGIS 8.x Network Analyst is in
  developmental stages

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What do the tools do?

• Direct path analysis
• Optimum routing
• Closest facility analysis
• Drive time analysis
• Driving directions

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How can this help me?

• Direct path Finding the shortest path between
  your house and a friends
• Optimum routing Helping a pizza deliveryman
  visit numerous houses in the most time
  efficient manner
• Closest facility Finding the closest hospital to
  an automobile accident

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How can this help me?

• Drive time analysis Helping a store determine
  how many customers are within 5 driving miles
• General driving directions Dont we all love
  Mapquest!

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How do they work?

• Activate Network Analyst extension

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How do they work?

• 2. Add network data

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How do they work?

• 3. All network functions can then be accessed

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However

• If street driving directions are desired,
  geocoding service must be activated

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More how tos

• To perform analysis, stops must be located on
  or near the network data
• These stops can be selected interactively, by
  manually entering addresses, or by loading a
  stops layer

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Interactive selection
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Manually entering address
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Loading a stops layer
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How does it determine the best routes?

• Network Analyst relies on impedances
• Default impedance is line length
• Can also be others, such as estimated travel time
• Values must be in attribute table and specified
  before analysis

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Sample calculation

• If you know line length and speed limit, a travel
  time can be estimated

5 mile street/30 miles per hour speed limit 60
min/hr 10 minutes
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How does it determine the best routes?

• One way streets-can be specified in attribute
  table (must specify allowed travel direction)
• Prohibited turns-can be specified in turntable
  (very tedious procedure)
• Under/Overpasses-can be specified in attribute
  table (add elevation fields)

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Now lets really see what kind of damage we can
do with this stuff!
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Demo Direct paths
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Demo Optimum routing
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Demo Closest facility
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Demo Service area
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Demo Mapquest directions
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Conclusions

• Network analysis can be performed fairly easily
  with ArcView 3.x Network Analyst
• However, to be accurate, lots of time must be
  spent in data preparation
• Could become more powerful and user-friendly with
  customization via Avenue programming
• All in all, its a very useful tool but it is not
  cheap!

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Any Questions?