Polygons which model areas of interest – counties, national parks, or property boundaries for example – are generally static. A new area of interest might be established requiring a geofence to be added, or an existing area’s geographic extent might occasionally change requiring a geofence to be updated, but in general the geofences don't change very often. This scenario fits well with GeoEvent Server’s ability to synchronize its geofences with a feature record set maintained as part of a feature service. The areas of interest can be maintained as feature records and occasionally imported to establish or update the relatively static geofences. A synchronization rule can periodically poll the feature service to obtain updates.
This blog explores a different scenario. Suppose you need geofences to be created dynamically, managed for only a short period of time, and then frequently and automatically destroyed when no longer needed. Constantly polling a feature service to check and see if there have been any changes is impractical.
In a dynamic scenario, we need to push changes to GeoEvent Server immediately as the changes are received. A video attached to this blog will show how a GeoEvent Service can be used to receive attributes describing an area of interest, compute an effective date/time range during which the area of interest is considered relevant, and generate a polygon to model the area of interest. A stream service will be used to broadcast dynamically generated polygons and computed date/time values as a feature records allowing them to be registered with GeoEvent Server as new or updated geofences via a synchronization rule.
- Import and review a pair of GeoEvent Services configured to process a tracked asset's current location and dynamic geofences constructed for a given center point of geographic interest.
- Review how stream services are published and configured outbound connectors updated to use the published stream services to broadcast processed event records as feature records.
- Use the GeoEvent Simulator to send simulated vehicle location observations to GeoEvent Server and display those locations, live, on a web map.
- Configure a synchronization rule to subscribe to a stream service and receive polygon feature records as they are broadcast (rather than relying on a feature service which must be frequently polled for updates).
- Demonstrate how information can be sent to GeoEvent Server, on demand, via HTTP/POST to drive the generation of dynamic areas of interest (e.g. geofences).
- Demonstrate the display and update of dynamic geofences both on a web map and in GeoEvent Server.
- Extend a GeoEvent Service with an analytic which detects when a tracked asset's location intersects a dynamic geofence and produce an alert message which can be displayed using the GeoEvent Logger.
- Discuss the temporal relevance of geofences, how analytics you configure will ignore geofences which are not temporally relevant, and how the GeoEvent Server AOI Manager automatically purges geofences which are no longer being used to clean-up its registry.
I have included demonstration resources with this blog post so you can recreate this demonstration in your own environment. An attached ZIP archive includes an XML snapshot of a GeoEvent Server configuration which includes a couple of GeoEvent Services as well as inbound and outbound connectors. The configuration file was taken from a 10.7.1 deployment, but should work in the upcoming 10.8 and 10.8.1 releases.
- A pre-configured GeoEvent Service Trackpoints connects a TCP/TEXT input with a stream service output to broadcast point feature records and report the location of a simulated tracked asset.
- A second pre-configured GeoEvent Service, AOI_Centerpoint, connects an HTTP/JSON input with a stream service output to buffer received point locations and broadcast each buffer as a polygon feature record suitable for use as a geofence.
- A video will walk you through the import of the provided configuration, necessary stream service publication, and the configuration of a geofence synchronization rule to subscribe to receive feature records broadcast from the second stream service.
I hope you find the video tutorial and information useful –