ArcGIS Velocity supports geofencing and dynamic geofencing in several of the real-time and big data analytic tools.
Geofencing is a form of real-time spatial analysis in which features (often track points) are assessed using areas of interest (often polygon areas). Most commonly, point-based observations are analyzed to determine if they have entered or exited a virtual perimeter.
In several real-time and big data analytic tools, geofencing can be performed to identify certain spatial relationships that may occur between features in a target feed or data source and a set of spatial join features, or geofences. The features used as geofences should be connected to the join port of the geofencing tool. Geofences can be points, lines, or polygons. The spatial relationships available depend on the geometry type of the input target and join data.
Example use cases for geofencing include the following:
- A logistics company wants to detect when a delivery vehicle is within 5 minutes of a delivery destination to send a message to the recipient.
- Target data—A feed of the delivery vehicle locations
- Join data (geofences)—A feature layer containing 5-minute drivetime polygons, pregenerated using ArcGIS network analysis tools
- An airport wants to turn on the automated landing lights when an aircraft is within its airspace.
- Target data—A feed of aircraft positions
- Join data (geofences)—A feature layer containing the authoritative airspace polygons
- A shipping company wants to track and detect when its vessels have deviated from their planned routes.
- Target data—A feed of AIS ship positions
- Join data (geofences)—A feature layer containing pregenerated expected routes for each ship or a buffer around these routes
The following real-time and big data analytic tools support geofencing:
If the join features (the geofences) do not change, use a static data source for the best performance. When a static data source is used, join features are collected once when the analytic starts and are not refreshed again until the analytic restarts.
In several real-time analytic tools, you can perform dynamic geofencing to identify spatial relationships between features in a target feed and a set of features in another join feed (the geofences), both of which are updating in real-time or near real-time. The tool performing the geofencing uses the most recent observation of any given track ID as geofences.
- If a feed is connected to the join port, the join features (the geofences) are continuously refreshed based on the incoming features in the join feed. In this case, geofencing is performed dynamically based on the changing features in both the target and join feeds.
- With dynamic geofencing, the Join Time Window parameter value is required.
- If the join feed does not have a field tagged END_TIME, and the last known observation for a join feature is older than the specified join time window, the observations are purged from the tool's memory and are not included in the analysis.
- If the join feed has a field tagged END_TIME, the feature age out of the geofence store according to the value in the field tagged as END_TIME or at the close of the join time window, whichever comes first.
Examples use cases for dynamic geofencing include the following:
- Analysts tracking vehicle activity want to define, modify, and delete areas of interest to detect entering and exiting vehicles. This includes updating areas of interest as they are created, updated, and deleted by the analysts and sending alerts to the appropriate analyst when a vehicle enters or exits any of the active watch zones. In this example, the dynamic geofencing tool uses continuously updated geofences, the active watch zones, as the analysts modify them.
- A logistics company wants to continuously track and monitor a data feed of severe weather polygons and alert their pilots in-flight who are within a certain proximity to a storm. In this case, the aircraft feed is the target data and the weather areas are the join data, or geofences. As weather information updates, the geofencing tool identifies the aircraft impacted.
- A city's transportation department tracks their maintenance vehicles in one feed and also receives a feed of events that may impact or endanger the vehicle or driver such as traffic jams, accidents, protests, or police activity. With each new vehicle observation, a dynamic geofencing tool identifies the nearest event (geofence) that has occurred within the last 15 minutes and the distance between the vehicle and that event.
The following real-time analytic tools support dynamic geofencing:
The maximum size of geofences supported in real-time analytics cannot exceed 768 MB.