Difference Creator Processor

Summary

The Difference Creator Processor can be used to determine the intersection between an event record’s geometry and a single event record. The processor clips or removes the portion of the geofence that intersects the event record’s geometry.

Examples

• Calculating the geometric difference between a geofence and an intersecting event record can show areas snow has been cleared by snow plows and areas where snow remains.
• Calculating the geometric difference between a geofence and an intersecting event record can show areas that have been searched by a field crew and areas that still need to be searched.
• Calculating the geometric difference between a geofence and an intersecting event record can aid with monitoring whether assets have touched, entered, or intersected a fixed boundary.

Usage notes

• The Difference Creator Processor requires two discrete geometries be specified. You cannot, for example, use a regular expression to specify several different geofences and remove the intersecting portions of each geofence from the event record’s geometry.
• The processor also requires the dimensionality of the geofence be equal to or greater than that of the event record's geometry. You cannot, for example, clip or subtract a point from a polyline or a polyline from a polygon.
• The processor requires the field containing the event record’s geometry be specified. A geometry field name can be specified, or the GEOMETRY tag can be applied to a field in a GeoEvent Definition to identify the geometry field.
• The Geometry Field parameter will show the name of every field from every GeoEvent Definition containing a data type of geometry. When selecting the geometry field by name, choose the name of the correct geometry field that corresponds to the event record’s GeoEvent Definition.
• The processor can be configured to replace the event record's geometry with the computed difference of the two geometries or place the difference into a new geometry field using the Replace Geometry parameter. Altering an event record's schema by adding a new field requires GeoEvent Server to create a new GeoEvent Definition. The new GeoEvent Definition will be managed by GeoEvent Server and deleted if changes are made to the processor or the GeoEvent Service in which the processor is used.
• Choosing Yes for the Tag the New Geometry Field as Geometry parameter explicitly tellsGeoEvent Server which geometry field should be treated as the event record’s realized geometry for subsequent processing or output.

Parameters

Parameter	Description
Name	A descriptive name for the processor used for reference in GeoEvent Manager.
Processor	The name of the selected processor.
Geometry Field	The name of the geometry field or the GEOMETRY tagged field from the inbound event record that the processor uses to calculate the geometric difference with an intersecting geofence.
Replace Geometry	Specifies whether to replace the current event record geometry with the geometry of the clipped geofence. The default is Yes. Yes - The event record geometry will be replaced with the geometry of the clipped geofence. No - The event record geometry will remain the same. The geometry of the clipped geofence will be stored in a new geometry field as a part of the event record. Altering an event record’s schema by adding a new field name requires a new GeoEvent Definition.
New Geometry Field Name (Conditional)	The name of the new geometry field where the clipped geofence geometry will be stored. This parameter is shown when Replace Geometry is set to No and is hidden when set to Yes.
Tag the New Geometry Field as Geometry (Conditional)	Determines whether the new geometry field created by the processor will be tagged as GEOMETRY. The GEOMETRY tag is used by GeoEvent Server to identify the event record’s realized geometry when multiple geometry fields are present. The default is No. This parameter is shown when Replace Geometry is set to No and is hidden when set to Yes.
New GeoEvent Definition Name (Conditional)	The name assigned to the new GeoEvent Definition. The new GeoEvent Definition will combine the schema of the inbound event record with the additional new geometry field. This parameter is shown when Replace Geometry is set to No and is hidden when set to Yes.
Geofence	The category and name of the geofence. . The processor uses the geofence to calculate the geometric difference with an intersecting event record. The resulting geometry is the clipped portion of the geofence. The required format for specifying a geofence is category/name, for example: Hurricanes/Doe AVL/Vehicle1

Considerations and limitations

• Consider replacing the existing event record geometry with the geometry representing the calculated difference prior to sending the event data to a feature service. Feature services only support one geometry type field, so whichever field has not been tagged as GEOMETRY will be converted and kept as a string.