The Union Creator Processor is used to produce a geometric union of an event record’s associated geometry with one or more geometries imported as geofences.
Examples
The following are example uses of the Union Creator Processor:
- The processor can be used to enhance the geometry of an event record with the geofences it intersects. The union of the geometries can be used in a post-processing workflow to indicate an overlay of geofences (or areas) where the event occurred.
- The processor can be used to create a multipoint feature from the real-time observations of a point event. Inbound point events can be sent to a feature service to be stored as geofences. Simultaneously, each new point event received can be used to union with the previous observations as geofences. The resulting geometry will be a multipoint feature combining the current point event observation with the near real-time collection of previous geofence event observations.
Usage notes
Keep the following in mind when working with the Union Creator Processor:
- The Union Creator Processor uses the event record's geometry and one or more geometries registered as geofences. For example, a regular expression can be used to specify several different geofences to determine the union.
- The processor requires the event record field containing the geometry be specified. A geometry field name can be specified or a GEOMETRY tag applied to a field within a GeoEvent Definition can be used to identify the geometry field.
- The processor can be configured to either replace the event record's geometry with the union of the specified geometries or place the union into a new geometry field using the Replace Geometry parameter. Adding a new field to a GeoEvent alters the event record's schema, which 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.
- Unlike other processors such as the Difference Creator Processor and the Symmetric Difference Creator Processor, which only operate with two discrete geometries, the Union Creator Processor accepts a regular expression, allowing several geofences to be specified. Consequently, the union of a received event record's geometry can be obtained with one or more geometries that have been imported as geofences.
Parameters
The following are the parameters for the Union Creator Processor:
| Parameter | Description |
|---|---|
|
Name |
A descriptive name for the processor used for reference in GeoEvent Manager. |
|
Processor |
Specifies the processor selected. |
| Geometry Field | The name of the geometry field or the GEOMETRY tagged field from the inbound event record the processor uses to calculate a union with geofences. |
| Replace Geometry | Specifies whether to replace the current event record geometry with the union of the event record’s geometry and the geofences. The default is Yes.
|
| New Geometry Field Name (Conditional) | The name of the new geometry field where the union of the event record and geofences geometry will be stored. The 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) | Specifies 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. The 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. The parameter is shown when Replace Geometry is set to No and is hidden when set to Yes. |
| Geofences | The category and name of the geofence registered with GeoEvent Server. The processor uses the geofence to calculate the geometric union with the event record’s geometry. The processor supports regular expressions, allowing multiple geofences in a category or multiple categories to be specified. The required format is category/name, specified as a pair of regular expression patterns, for example:
Note:Multiple geofence category/name expressions cannot be specified as a comma separated list. For example, specifying Countries/France, Countries/Germany cannot be used to specify the geofences France or Germany. Note:Regular expressions are used for both the category and the name. The expression .*/.* includes all geofences in all categories. Remember, regular expression pattern matches are case-sensitive. |
Considerations and limitations
There are several considerations to keep in mind when using the Union Creator Processor:
- Consider the geometry of the participating event record and geofences when configuring the Union Creator Processor. For example, the union of an event record’s point geometry with a geofence whose geometry is a polygon will result in the polygon geometry only. In contrast, the union of an event record’s polygon geometry with a geofence whose geometry is also a polygon will result in the polygon geometry of both.
- Consider replacing the existing event record geometry with the union geometry prior to sending the event data to a feature service. Feature services only support one geometry type field and therefore whichever field has not been tagged as GEOMETRY will be converted and kept as a string.