pgRouting is an extension of PostgreSQL that allows for shortest path searches in real road networks. It includes algorithms like Dijkstra, A*, and Shooting* for finding shortest paths as well as functions for traveling salesperson problems and driving distance polygons. pgRouting integrates its C++ core for routing algorithms as a library with PostgreSQL using C wrappers and PL/PgSQL functions. It can model real-world road networks that have attributes like turn restrictions, traffic lights, and parallel edges.

1. FOSS4G2007
Presentation
Shortest path search in real
road networks with
pgRouting
pgRouting Anton Patrushev (Orkney, Inc.)
Shortest path search in real road networks
with pgRouting 1

2. Introduction
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.
pgRouting includes:
* Shortest path search (Dijkstra, A*, Shooting*)
* Traveling Salesperson Problem (TSP) solution
* Driving distance polygon calculation
Shortest path search in real road networks
with pgRouting 2

3. How it works
Pl/PgSQL SQL query
C++ core C wrapper
function (data)
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4. Shortest path algorithms
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Dijkstra
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Well known and fair shortest path algorithm
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Always finds mathematically shortest path
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Good for sparse networks
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A*
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Well known heuristic shortest path algorithm
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Needs vertex geometry information
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Searches through less number of vertexes
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Good for dense networks
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Shooting*
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5. Shooting*
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Edge­based heuristic shortest path algorithm
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Supports maneuver restrictions and traffic lights
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Properly processes parallel edges
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Good for dense networks
Predecessors:
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Modified A* ­ Wolfgang Schmid, 2000, Stephan Winter, 2002
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C* ­ Ingrid Flinsenberg, 2004
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6. Comparison with other
algorithms
Dijkstra cost=cost(vertex1, vertex2)
Each vertex can be visited only once
A* cost=cost(vertex1, vertex2)+H(vertex1, vertex2)
Each vertex can be visited only once
Shooting* cost=cost(edge1)+cost(edge1, edge2)+H(edge1)
Each edge can be visited only once
Parallel edges handling
Dijkstra/A* Shooting*
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7. Real road networks
A B C
A)Signs (restrict maneuvers)
B)Traffic lights (delays)
C)Road marking (restrict maneuvers)
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8. Network representation
d d c
f
d
a b c a b c
cost(eb,ab)=1min a b
cost(eb,bd)=1min
cost(eb,bc)=∞ cost(eb,bc)=1min cost(ab,bd,df)=∞
e e ... e
B ...
A C
...
A)Right turn costs too much
B)Driving through vertex b passage costs extra
C)Driving from a to f costs too much
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9. Routing data structure
Dijkstra
A*
Shooting*
Edge Edge Edge
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id
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id ●
id
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cost
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cost ●
cost
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reverse_cost
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reverse_cost ●
reverse_cost
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Source vertex
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Source vertex ●
Adjacent edge
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id
●
id ●
rule
●
Target vertex
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x ●
to_cost
●
id
●
y ●
Source vertex
●
Target vertex ●
id
●
id ●
x
●
x ●
y
●
y ●
Target vertex
●
id
●
x
●
y
Shortest path search in real road networks
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10. Thank you!
pgrouting.postlbs.org
orkney.co.jp
pgRouting
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