How does the access analysis report determine accessibility of sport facilities for a defined population?
Active Places Power uses one of Esri’s Network Analyst routing solvers to provide dynamic Origin to Destination (OD) routing analysis. This is achieved via the ArcGIS Server Network Analyst extension geo-processing web service. The solver type used in the Access Analysis is the OD Matrix Analysis. It performs the cost of travel in time or distance from multiple origins to multiple destinations.
Two separate network datasets (driving model or walkingmodel) are used to compute the routing from multiple Output Area Centroids to multiple Facilities given a set of conditions. For the Drive option Ordnance Survey's Integrated Transport Network (ITN) Layer is used whereas for the Walk option, ITN is combined with the Ordnance Survey's Urban Path data.
In the walking option motorways are avoided and all traversable roads are assigned a speed of 3 MPH. In the driving option the 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.
With the Network Analyst OD Matrix solver, you can create an origin-destination travel time/distance cost matrix from multiple origins to multiple destinations. An OD cost matrix result contains the network impedance from each origin to each destination in accordance to specified cut-off criteria.
The best network path is discovered for each origin-destination pair, and the cost (travel time or distance) is stored in the attribute table of the output lines. Even though the map shows straight lines from origins to destinations for performance reasons, the attributes of the lines store the actual traversed network route cost, not the straight-line cost.
The user journey involves selecting an Area of Interest from the available list. The user can then choose to show population data and subsequently set the travel parameters. Parameters include choice of driving or walking and whether time or distance it to be used as a cut-off parameter. The system then submits this information to the ArcGIS Server Network Analyst solver to compute. When the process is completed the user gets notification to view the result.
The resulting map shows the lines of connection between the origin Population centroids and the destination Facility that were reachable given the cut-off parameters. Population Centroids that were unable to reach a Facility due to the cut-off parameters are shown as red dots.
The OD Matric calculation is an intensive process and thus the larger the Area of Interest, the more time it takes to compute the results.