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How are the catchment areas (drive and walking) generated and which datasets are used?

Active Places Power uses ESRI's ArcGIS Server Network Analyst 10 software to provide dynamic catchment area analysis.

For more information on ESRI's Network Analyst see:
http://www.esri.com/software/arcgis/extensions/networkanalyst/index.html

The two separate network datasets are used to compute the catchment areas within the Catchment Profile Report.  For the driving option Ordnance Survey's Integrated Transport Network (ITN) Layer is used whereas for the for the walking option,  ITN is combined with and Ordnance Survey's Urban Path data. In the walking option motorways are avoided and all traversable roads are assigned a speed of 3 MPH. 

It should be noted that Ordnance Survey ITN road speed limits have not been used. Instead the entire ITN dataset has been assigned articulated speed limits determined through Sport England's Facility Planning Model (FPM). This includes for example junction delay factor of 15% (of the total Drive Time) and an additional 160 Secs (2.667 Mins) to factor in parking delays at start and end of each journey. This ensures a consistent calculation of drive times used within both Active Places Power and the Facility Planning Model.

The ArcGIS Server Network Analyst extension computes catchment areas (isochrones) around any location on the network whether this be an existing facility or a new user defined location.  The service area will encompass all accessible streets that are within a specified impedance. For example, the 5-minute catchment area for a point on a network includes all the streets that can be reached within five minutes from that point.  A service are for a given point is simply the polygon areas defined by specific time limit breaks (i.e. 5, 10, 15, 20 , 25, 30, and 35 minutes).

The resulting isochrones are then intersected with profile data (point in polygon) to create the required report information. For example, population centroids within each catchment area are selected and aggregated to provide a total population count.

For more information on the Ordnance Survey data products see:
ITN - http://www.ordnancesurvey.co.uk/oswebsite/products/os-mastermap/itn-layer/index.html
Urban Path - http://www.ordnancesurvey.co.uk/oswebsite/products/os-mastermap/itn-layer/urban-paths.html

For more information on ESRI's Network Analyst see:
http://www.esri.com/software/arcgis/extensions/networkanalyst/index.html