The Analysis Region represents the geographical extents and granularity of the calculations performed by Overture. It also specifies the projection that should be used during calculation.

By default, the analysis boundary will be calculated automatically from the distribution of sites in the network.

Visualizing the Analysis Boundary

The Analysis Region map layer shows the current analysis boundary on the map as a dotted line as shown below.

Accessing the Analysis Region Component

You can also access the properties of the analysis region component from the Analysis > Region menu option:

This will display the properties of the Analysis Region in the Properties Window:

Properties

The analysis region component has the following settable properties:

• Analysis Projection. The projection that will be used in all calculations and analyses.
• Bin Size. The minimum bin size to use when running network analyses. For geocentric analysis projections (that use linear distance) the value will be used directly, for geodetic analysis projections (that use angular distance) the resolution will be calculated with reference to the middle of the analysis boundary.
• Border Size. The distance to extend the analysis boundary to ensure the edge of the network is correctly analyzed.
• Region Provider. An optional Region Provider to use for the analysis boundary. Note that the analysis boundary must always be rectangular, so a bounding box will be placed around the regions.

The settings of the above control the following derived properties:

• Analysis Boundary. This is the actual boundary that will be used for analysis. The boundary is aligned with the underlying projection and grid structure as specified by the resolution.
• Analysis Dimensions. The dimensions of the analysis region (the number of bins) as dictated by the boundary and resolution.
• Analysis Resolution. The resolution that will be used in all calculations and analyses in units appropriate to the selected projection.

Actions

The analysis region component has the following actions:

• Zoom To Analysis Boundary. Move the map viewport such that the whole of the analysis boundary is visible.

Remarks

The analysis boundary is calculated from a bounding rectangle around either the site locations or an optionally specified Region Provider. The Border Size is added to this bounding rectangle in all directions.

The Analysis Dimensions tells you the total number of bins that must be processed by Overture during a calculation. The performance of Overture is proportional to this number: more bins means that Overture must do more work to produce a result. In the early stages of a project, you may wish to increase the bin size to give a faster but coarser result; this can then be refined when final results are to be produced. You may also wish to use Overture's Express Point technology, which allows the size of the bins to vary in proportion to the underlying traffic distribution.

Analysis can be performed in any region-appropriate projection even if the input data to the analysis are in a mix of different projections. It is not recommended to change the projection from the default WGS84 unless required to for compatibility with other mapping tools.