Scope and Buffer Regions

When selecting data by area, consider the scope of any Rules or Actions run in your session.

The scope of a Rule or Action is the minimum area required to check conformance.

For a Rule that checks every point is within 100 units of another point, the rule scope should be a circular area centred on the point of interest, with a radius of 100 units.

In some cases, the Rule scope is not completely known so a check may produce a false result.

Additional areas outside of the known region must be taken into consideration to obtain correct results.

For example, if the scope is outside the boundary of known data, a false negative is returned when checking for points within 100 units of the root point.

Example: scope falls outside the data boundary

To counteract this, you can set a Buffer.

The Buffer parameter can be used when data is selected using the following methods (see Opening and Selecting Data):

Single polygon
Multiple polygons
Bounding Box
WKT polygon

The Buffer is measured in dataset units (typically meters), and the default is 0. Decimal degrees for latitude and longitude can also be used.

In our example, a buffer of 101 could be set to ensure all conformance checks will be valid.

For a region that is defined by a rectangle, the initial rectangular area exists for the scope, while a larger rounded rectangle covers the buffer.

The coordinates in the example below show the initial rectangular and the larger rectangle (buffer region).