pgRouting presentation given at FOSS4G UK on 15 June 2016

1. Using Ordnance Survey
datasets with pgRouting
Ross McDonald
Angus Council
@mixedbredie

2. “The person
attempting to travel
two roads at once will
get nowhere.”
- Xun Zi
Contains OS Open Data Crown Copyright and Database Right 2016.

3. What is it?
An extension to the PostGIS enabled
PostgreSQL database to add geospatial
routing functionality.

4. Why use it?
• Free (as in freedom)
• Flexible (as in open source)
• Functional (as in fully featured)
• Fun (if you’re that way inclined)

5. http://www.cartographicperspectives.org/index.php/journal/rt/printerFriendly/c
What does it need?

6. CC-BY-NC-SAReproducedwiththepermissionoftheNationalLibraryofScotland
Where can one get such things?

7. Data, data everywhere
• OS Open Roads
• OS Meridian2
• OS Strategi
• OS ITN
• OS Highways
• OS Water Network

8. OpenStreetMap
Metro extracts by Mapzen

9. "name1" IN ('Watling
Street','Fosse Way',
'Ackling Dyke', 'Akeman
Street', 'Cade''s Road',
'Dere Street', 'Ermin
Way', 'Devil''s
Causeway', 'Devil''s
Highway', 'Ermine
Street', 'Fen Causeway',
'Icknield Street', 'King
Street', 'Maiden Way',
'Military Way', 'Peddars
Way‘, …)
https://dhs.stanford.edu
/spatial-
humanities/geographic-
networks-pgrouting/
/en.wikipedia.org/wiki/Roman_roads_in_Britain#/media/File:Roman_Roads_in_Britannia.svg

10. But first you gotta be loaded
• For OS data
– Astun Loader!
– Lutra’s OS Translator II
– Ogr2ogr
– Snowflake’s GoLoader*
– Safe’s FME*
• For OpenStreetMap
– osm2pgrouting

11. There’s a plugin for that
• How can I use it
without writing
SQL?
• pgRouting Layer by
Anita Graser and
others in the
pgRouting team

12. CC-BY-NC-SAReproducedwiththepermissionoftheNationalLibraryofScotland
“Most roads lead men
homewards, my road leads
forth.”
John Masefield

18. PostgreSQL function to loop through each input
point and calculate Djikstra shortest path to every
node on the network…
pgRouting 1.0.7-dev

19. pgRouting 2.2.3
• Using pgr_drivingdistance and
pgr_alphashape
• Using an all-in-one function to process
multiple input points
IMPROVED

26. Performance Enhancements
• Index your data
• Add a Bounding Box to
your query
• Make it easier for the
user

27. Vanilla Shortest Path
SELECT seq, id1 AS node, id2 AS
edge, cost FROM pgr_dijkstra('
SELECT gid AS id, source::integer,
target::integer, cost_time::double
precision AS cost,
rcost_time::double precision AS
reverse_cost FROM or_network',
100828, 1136587, false, true);

28. M&S Shortest Path
SELECT seq, id1 AS node, id2 AS edge,
cost FROM pgr_dijkstra(' SELECT gid AS
id, source::integer, target::integer,
cost_time::double precision AS cost,
rcost_time::double precision AS
reverse_cost FROM or_network
WHERE geometry && ST_Expand( (SELECT
ST_Collect(the_geom) FROM
or_network_vertices_pgr WHERE id IN
(100828, 1136587)),5000)', 100828,
1136587, false, true);

29. Making things even better!
• Update the QGIS plugin to use new PGR
functions
• Update the plugin to use a bounding box
• Add restrictions (e.g. closures, safe
routes)
• How does psycopg2 work? Is it a
bottleneck?

30. Not Mrs Beeton’s recipes
http://anitagraser.com
https://georepublic.info/en/blog
http://workshop.pgrouting.org/index.html
http://ghost.mixedbredie.net/tag/pgrouting

31. CC-BY-NC-SAReproducedwiththepermissionoftheNationalLibraryofScotland
Thank you
Ross McDonald
Angus Council
mcdonaldr@angus.gov.uk
@mixedbredie
01307476419