Ring Definition

In a Ring Accumulation analysis, Ring Definition enables you to define the ring radius and damage ratio for each ring.

You can create a single ring on each location or a set of concentric rings. The concentric ring option is not available for Dynamic Ring Analysis because this type of ring analysis generates rings after the analysis. It is also not available for Grid Ring Analysis.

Users can choose not to generate multiple rings on the same latitude/longitude. Each ring around a location (single ring or multiple rings) acts as a single accumulator or as a single event. In the case of concentric rings, each band in the concentric ring acts as a sub accumulator and the damage ratio is applied based on that band. The latter option can be useful for modeling fire or terrorism events.

Procedure

To define a ring as an accumulator:

After selecting (Ring Accumulation) as the analysis type, select Step 2 - Configure.
On the Accumulate tab, in the Ring Definition area, click (Add new concentric ring).
In the Radius field, enter a decimal number.

If you are going to select kilometers and miles as the unit of measurement, enter a decimal number greater than "0".

In Geospatial Analysis, when you select Override Recommended Radius for a Dynamic Ring Analysis, the minimum ring size is one foot and the recommended maximum ring size is 1000 meters or 1 mile (1069 meters).
In the Unit field, select the unit of measurement (feet, kilometers, meters, or miles).
In the Damage Ratio field, leave the default (100.00%) or enter a percentage.

Results

The radius and damage ratio of each ring are defined and ready for the Ring Accumulation analysis.

Usage notes

The following table summarizes the defaults for the Radius field. The default radius is smaller for Dynamic Ring and Grid Ring analyses because larger rings, which may generate more potential ring points, increase the analysis time.

Table 1. Defaults for the Radius field
Exposure Type	Dynamic and Grid Ring Radius	Radius for Non-Dynamic Rings
Property Exposure	200.00 meters	500.00 meters
Workers' Compensation	200.00 meters	500.00 meters
Combined Exposure	200.00 meters	500.00 meters

For Dynamic Ring analyses, if you specify a radius greater than 1.0 kilometers or miles, you must also select the Override Recommended Radius option.
You can create multiple concentric rings for supported ring accumulation analyses. The concentric ring radiuses must be in ascending order, for example, 100, 200, 400, 500.
For Grid Ring analyses, there is a Grid Spacing field. The default grid spacing is "50". Touchstone defaults to a radius of 200.00 meters and grid spacing of 50.00 meters; you can change all the values. For best performance, AIR recommends that the grid spacing be ¼ of the radius size.