Event data frequently expresses coordinate values in geographic space using latitude and longitude. The Projector Processor can be used to project an event record’s geometry from its native coordinate system to another spatial reference. For example, you might want to explicitly project event data to review its coordinate values in the context of a specific coordinate system.
Examples
The following are example uses of the Projector Processor:
- The Projector Processor can be used to explicitly project event records to a different coordinate system before additional filtering or processing occurs in a GeoEvent Service.
- Use the processor when you want to use a specific geographic transformation method for moving your real-time data from one geographic coordinate system to another.
Usage notes
Keep the following in mind when working with the Projector Processor:
- It is recommended you understand the native coordinate system of your event data and how it relates to other spatial data you may have imported such as geofences. ArcGIS Server and GeoEvent Server typically project geometries as needed so spatial evaluations are conducted in a common spatial reference. ArcGIS Server will project data it receives to match a feature service's spatial reference, for example, before creating or updating features. GeoEvent Server will project spatial data on the fly before evaluating the data for intersection with a geofence.
- The processor requires a field containing the geometry be specified. You can specify either the event record field name or a tag applied to a field within a GeoEvent Definition that identifies the geometry field.
- The processor requires the well-known ID (WKID) of the coordinate system to which the inbound event data will be projected. The WKID for the WGS 1984 world geographic coordinate system, for example, is 4326. For more information on available coordinate systems, see Using spatial references.
- The processor can be configured to replace the event record's geometry with the projected geometry or place the projected geometry into a new field. 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.
- When using a user-defined transformation, at a minimum, it is necessary to specify a step one geographic transformation using an appropriate WKID (WKT). A geographic datum transformation WKID such as 108190 (for WGS_1984_(ITRF00)_To_NAD_1983) can be used with a forward directionality to transform an inbound event record’s datum from WGS 1984 to NAD 1983, for example. The event record geometry can then be projected to a spatial reference whose datum shares NAD 1983.
- When using a user-defined transformation, it is sometimes necessary to specify a step one and step two geographic transformation to obtain greater accuracy from the datum transformation. For more information, see Geographic transformation methods.
- An example of a step one and step two geographic transformation in ArcGIS Desktop would be WGS_1984_(ITRF00)_To_NAD_1983 + NAD_1927_To_NAD_1983_NADCON. This geographic transformation could be used to essentially transform a feature record’s datum from WGS 1984 to NAD 1927.
- The same geographic transformation in GeoEvent Server would need to be specified as WKID 108190 (WGS_1984_(ITRF00)_To_NAD_1983) for the step one geographic transformation. Its directionality is forward to first transform WGS 1984 to NAD 1983. The step two geographic transformation would then need to be defined as WKID 1241 (NAD_1927_To_NAD_1983_NADCON). Its directionality is reverse to transform the NAD 1983 to NAD 1927.
Parameters
The following are the parameters for the Projector 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 field tagged with the GEOMETRY tag from the inbound event data the processor uses to perform spatial projections. |
| Replace Geometry | Specifies whether to replace the current event record geometry with the projected geometry. The default is Yes.
|
| New Geometry Field Name (Conditional) | The name of the new geometry field where the projected 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 with the GEOMETRY tag. 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. |
| Output Spatial Reference | The outbound event record’s spatial reference. The spatial reference is defined by either a well-known ID (WKID) or well-known text (WKT). The WKID or WKT is used to perform the projection on the inbound event record’s geometry. Note:For more information on available coordinate systems, see Using spatial references. For more information on spatial references, see Spatial references. |
| User Defined Transformations | Specifies whether to use a geographic transformation defined manually or an automatic geographic transformation method. The default is No.
|
| Input Spatial Reference (Conditional) | The inbound event record’s spatial reference. The spatial reference is defined by either a well-known ID (WKID) or well-known text (WKT) and is used for the geographic transformation. There is no default for this parameter, for example:
Note:For more information on available coordinate systems, see Using spatial references. For more information on spatial references, see Spatial references. The parameter is shown when User Defined Transformations is set to Yes and is hidden when set to No. |
| Step One Geographic Transformation (Conditional) | The well-known ID (WKID) or well-known text (WKT) identifying the step one geographic transformation. The WKID or WKT refers to the geographic transformation and not the output spatial reference, for example:
Note:For more information on available geographic transformations and their WKIDs, see Using spatial references. For more information on geographic transformation methods, see Geographic transformation methods. The parameter is shown when User Defined Transformations is set to Yes and is hidden when set to No. |
| Step One Geographic Transformation Direction (Conditional) | The direction of the step one geographic transformation. While a geographic transformation is always defined in a specific direction (forward), the opposite can be used (reverse). Transformations are bidirectional. The default is Forward.
The parameter is shown when User Defined Transformations is set to Yes and is hidden when set to No. |
| Step Two Geographic Transformation (Conditional) | The well-known ID (WKID) or well-known text (WKT) identifying the step two geographic transformation. The WKID or WKT refers to the geographic transformation and not the output spatial reference, for example:
Note:For more information on available geographic transformations and their WKIDs, see Using spatial references. For more information on geographic transformation methods, see Geographic transformation methods. The parameter is shown when User Defined Transformations is set to Yes and is hidden when set to No. |
| Step Two Geographic Transformation Direction (Conditional) | The direction of the step two geographic transformation. While a geographic transformation is always defined in a specific direction (forward), the opposite can be used (reverse). Transformations are bidirectional. The default is Forward.
The parameter is shown when User Defined Transformations is set to Yes and is hidden when set to No. |
Considerations and limitations
There are several considerations to keep in mind when using the Projector Processor:
- Unless a specific geographic transformation is necessary, it is recommended you leave the User Defined Transformations parameter set to No. The processor will handle the geographic datum transformation automatically.
- It is recommended the Projector Processor be used at the start of a GeoEvent Service. This ensures inbound event records are in a common spatial reference with other geographic data used in other processing elements in a GeoEvent Service (for example, geofences or feature records from a Field Enricher (Feature Service) Processor).
- Consider replacing the existing event record geometry with the projected 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 with the GEOMETRY tag will be converted and kept as a string.