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Network Analysis

Network Analysis. By Josh Bundick EVSC 468 – Advanced GIS March 27, 2003. 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. What is a network?.

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Network Analysis

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  1. Network Analysis By Josh Bundick EVSC 468 – Advanced GIS March 27, 2003

  2. 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

  3. What is a network? Any system of interconnected linear features

  4. What is network analysis? • Solving problems involving networks • Goal is efficiency – Saving time and money

  5. What tools are needed? • Network data (connectivity is needed) • Network analysis software – A GIS!

  6. 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

  7. What do the tools do? • Direct path analysis • Optimum routing • Closest facility analysis • Drive time analysis • Driving directions

  8. How can this help me? • Direct path: Finding the shortest path between your house and a friend’s • 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

  9. How can this help me? • Drive time analysis: Helping a store determine how many customers are within 5 driving miles • General driving directions: Don’t we all love Mapquest!

  10. How do they work? • Activate Network Analyst extension

  11. How do they work? 2. Add network data

  12. How do they work? 3. All network functions can then be accessed

  13. However………… • If street driving directions are desired, geocoding service must be activated

  14. 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

  15. Interactive selection

  16. Manually entering address

  17. Loading a “stops” layer

  18. 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

  19. 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

  20. 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)

  21. Now let’s really see what kind of damage we can do with this stuff!

  22. Demo – Direct paths

  23. Demo – Optimum routing

  24. Demo – Closest facility

  25. Demo – Service area

  26. Demo – “Mapquest” directions

  27. 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, it’s a very useful tool but it is not cheap!

  28. Any Questions?

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