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Shortest path search for real road networks and dynamic costs with pgRouting



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This presentation will show the inside and current state of pgRouting
development. It will explain the shortest path search in real road
networks and how the data structure is important for getting better
routing results. We will show how you can improve the quality of the search with dynamic costs and make the result look closer to the reality. We will demonstrate the way of using pgRouting together with other Open Source tools. Also you will learn about difficulties and limitations of implementing routing functionality in GIS applications, the difference between algorithms and their performance.

pgRouting is an extension of PostgreSQL and PostGIS. A predecessor of
pgRouting - pgDijkstra, written by Sylvain Pasche from Camptocamp, was
extended by Orkney (Japan) and renamed to pgRouting, which now is a part of the PostLBS project.

pgRouting can perform:
* shortest path search (with 3 different algorithms)
* Traveling Salesperson Problem solution (TSP)
* driving distance geometry calculation

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Shortest path search for real road networks and dynamic costs with pgRouting

  1. 1. Shortest path search for real road networks     Anton Patrushev
  2. 2. What is pgRouting?    
  3. 3.     Shortest path
  4. 4.     TSP and DD
  5. 5.     VRP (DARP)
  6. 6. Real road networks How do they look like?    
  7. 7. Like this...    
  8. 8. ...or like this...    
  9. 9. ...or sometimes like this.    
  10. 10. What makes them real? traffic lights signs road marking    
  11. 11. How pgRouting can help here?    
  12. 12. gid, source, source target, cost, reverse_cost, x1, y1, x2, y2, rule, to_cost target    
  13. 13. Traffic lights make you slower. It means we should increase costs.    
  14. 14. B C 1min A D cost(A)=cost(A)+30sec cost(B)=cost(B)+30sec cost(C)=cost(C)+30sec     cost(D)=cost(D)+30sec
  15. 15. Signs tell you about   restrictions and road types.  
  16. 16.    
  17. 17. cost(A)=length(A) reverse_cost(A)=∞ A    
  18. 18. Sometimes the costs have different meaning.    
  19. 19. cost(A)=length(A)/2 reverse_cost(A)=length(A)*2 cost(B)=length(B)*3 reverse_cost(B)=length(B)/3 B   A  
  20. 20. Turn restrictions obviously restrict turns.    
  21. 21. B C 1min A D cost(A)=cost(A)+1min cost(B)=cost(B)+1min rule(A)="D" cost(C)=cost(C)+1min to_cost(A, D)=∞     cost(D)=cost(D)+1min
  22. 22. Road type signs can be used for cost calculation.    
  23. 23. Not only types, but also conditions.    
  24. 24. What about road marking?    
  25. 25. It separates lanes, ...    
  26. 26. ...specifies road types, ...    
  27. 27. ... and restrictions. C A D B E rule(D)="A, B"   to_cost(D)=∞  
  28. 28. And you know what's cool about pgRouting?    
  29. 29. All costs are dynamic. Which is opposite to pre-calculated.    
  30. 30. If the road is closed, ...    
  31. 31. ... there is an accident, ...    
  32. 32. ... a sign with restrictions limited in time, ...    
  33. 33.   ... bad weather conditions, ...  
  34. 34. ... or an obstacle, ...    
  35. 35. You don't need to rebuild and reload     your network...
  36. 36.   ... and wait forever.  
  37. 37. You only need to adjust the cost for this particular road. And next search will go another way.    
  38. 38. Cost can be virtually     anything.
  39. 39. It is possible to use pgRouting with OSM data.    
  40. 40. pgRouting can be used for different kinds of networks.    
  41. 41. Canals and rivers, ...    
  42. 42. ... hiking trails, ...    
  43. 43. ... or any other kind of network.    
  44. 44. Now it's showtime!    
  45. 45. Thanks to for being the best free photo stock. Thanks to people who put their photos to  flickr under Creative Commons license.    
  46. 46. Just want you to remember    
  47. 47.    
  48. 48.