Part 3: Building a routable network
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These pages provide a guide to building a routable network using what are four of the most popular routing software packages used across the public sector. However, they are not intended to be a comprehensive guide to creating a network, or an endorsement of the packages. Please refer to the documentation for the specific software to be used. Furthermore, a working knowledge of the software is required before starting this type of analysis.
To simplify this the methodology has been broken down into sections: Before Starting, Network Analyst (ESRI), Routefinder, Cadcorp SIS and pg Routing to make it easier to jump to the section you are interested in.
Before starting to build a routable network there are several options to consider that will determine which data is required and which option is most appropriate to build your network.
What level of analysis is required? This will determine the level of detail in your network. If a high-level strategic overview is needed, then consider using OS OpenRoads data as the basis. However, if more detailed analysis, looking at service location and journey times is needed, this will require either OS MasterMap Highways or OS NGD Transport Network data.
What extent of data is required? Consider whether a network for Great Britain or just your local area is required. The bigger the area the longer it will take to build the network and the slower the analysis may be.
What additional data needs to be added? – For example, road speeds, bus stops for public transport networks and so on.
Some networks will be built with speed attributes set to nominal values which you may need to review and amend.
What type of analysis is required? For example, drive time buffers, A to B routing and so on
How to run the analysis? Typically, network analysis is memory intensive, and it may be more efficient to analyse the data in smaller batches or by using a smaller network.
How will the results be presented? Are the results going to be presented graphically in a report or do you just require a spreadsheet of values.
What are the processing requirements for the intended software?
Examples
With ever tighter financial pressures on Public Services a few Local Authorities have looked to using network analytics to improve services and reduce costs. Ordnance Survey has collected several cases studies demonstrating the use of the network data in route optimisation for waste collection and school bus routing. Full details of all Ordnance Survey case studies can be found at - .
Please note: This is a methodology and not an OS product. The methodology can be taken and adapted, but OS will not be maintaining this methodology.
To convert the Highways GML into a TAB file for use with RouteFinder a translator is available that can be downloaded from - . There are separate TAB files for both roads and paths data so both can be loaded together or as separate networks. Click ‘Add Files’ and select the GML for translation. To include the restrictions which are part of Highways you will need to check ‘TOID base (turn.txt)’ and click ‘Go!’.
There are several resources for loading data into PostGreSQL and making available to pgRouting. The data can be loaded into the database using the Astun Loader made available on GitHub - .
Creating a network for use with pgRouting involves running SQL queries in a PostGreSQL database with the PostGIS extension. Several useful resources are available on GitHub. This include a guide written by Ross MacDonald for pgRouting which can be found here - . As well as that of Tim Manners - .
Further details on pgRouting - .