Shortest Path Search with pgRouting
Daniel Kastl
What is pgRouting ?
An Extension for
PostgreSQL / PostGIS, ...
An Open Source
project, ...
A Library providing, ...
Shortest Path
Driving Distance
Traveling Salesperson
v2.0
Feature Highlights
➔ Two new All Pairs Short Path algorithms
➔ Bi-directional Dijkstra and A-star algorithms
➔ One to many nodes shortest path search
➔ New TSP solver (with distance matrix)
➔ Turn Restricted shortest path (replaces Shooting
Star algorithm)
➔ A collection of useful utility and graph analytics
functions
More Highlights
➔ Modular library design
➔ Unit tests and automated tests with Travis
➔ Compatibility with PostgreSQL 9.1+ / PostGIS 2.0+
➔ Installs as PostgreSQL EXTENSION
➔ Added pgr_ prefix to functions and types
➔ Improved build process for Windows
➔ Better documentation in several languages
https://www.transifex.com/projects/p/pgrouting/
Most users need pgRouting for
Road Networks
How do they look like?
Like this ...
… or like this ...
… or sometimes like this.
What makes them real?
Traffic lights Signs Road marking
pgRouting extends
PostgreSQL/PostGIS
CREATE EXTENSION postgis;CREATE EXTENSION pgrouting;
SQL Function
SELECT * FROM pgr_dijkstra(' SELECT gid as id, source::integer, target::integer, length::float8 as cost FROM ways', 30, 60, false, false);
Query Result
seq | node | edge | cost -----+------+------+--------------------- 0 | 30 | 53 | 0.0591267653820616 1 | 44 | 52 | 0.0665408320949312 2 | 14 | 15 | 0.0809556879332114 3 | 13 | 14 | 0.072694271986776 4 | 12 | 13 | 0.081239348480584 5 | 11 | 12 | 0.00746935522787469 6 | 10 | 6869 | 0.0164274192597773 7 | 59 | 72 | 0.0109385169537801 8 | 60 | -1 | 0(9 rows)
gid,source,target,cost,reverse_cost,x1, y1,x2, y2,rule, to_cost
source
target
Traffic lights slow down
… so costs must increase.
1 min
cost(A) = cost(A) + 30seccost(B) = cost(B) + 30seccost(C) = cost(C) + 30seccost(D) = cost(D) + 30sec
B C
D
A
cost(A) = length(A)
reverse_cost(A) = ∞
A
Sometimes
the costs
have different
meaning.
A
B
cost(A) = length(A) / 2
reverse_cost(A) = length(A) * 4
Road type can be used
for cost calculation.
Not only road types
but also conditions
And you know
what is great about pgRouting?
All costs are dynamic!
… which is the opposite to pre-calculated
If the road is closed ...
… or there is an accident, ...
… there is a sign with restrictions limited to a certain time, ...
… bad weather conditions ...
You don't need to
rebuild and reload
your network
You only need to adjust the cost
for this particular road,
… and the next search will go another way.
Flexiblity vs. Speed
Cost can be virtually
anything
pgRouting can be used for
different kinds of networks
Canals and Rivers
Hiking trails
… or any other kind of networks
pgRouting can be enhanced
with custom functions
SELECT * FROM ctg_drivingdistance( ST_SetSRID( ST_MakePoint(-117.1078764,32.7111995),4326), 'ways', '2500,5000,7500', 'm');
Roadmap for Version 2.1
➔ Add “Multi-modal public transit routing”
(GSoC 2011)
➔ Add “Time dependent shortest path” algorithm
(GSoC 2011)
➔ Add “Two Queue” Algorithm (GSoC 2012)
➔ Add DARP and VRP (GSoC 2013 and 2014)
➔ Add Graph network partitioning (GSoC 2013)
➔ …. further improvements and bug fixes.
Tour Optimization & VRP
https://github.com/pgRouting
Website: pgrouting.org
Documentation: docs.pgrouting.org
Workshop: workshop.pgrouting.org
Support: pgrouting.org/support.html
More Information
… or talk contact us directly:
➔ Twitter: @dkastl
Photos from sxc.hu and
flickr under Creative Commons Licence.
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