HERE Tracking Developer's Guide

Transitions

A transition event is created every time a device enters or exits an associated geofence. These events are stored in the transition log.

This log also includes details of events where a device 'almost' crossed a geofence boundary. Device positions determined through GPS, WiFi or other methods have a range of uncertainty about them. This uncertainty is typically represented as a radius around the recorded point showing the accuracy of the position.

These are times when the accuracy radius reported around a device interesects with the geofence boundary but where it is not possible to confirm what side of the geofence boundary the device is on. This returns those events as well as total transitions.

There are three types of transition event:

  1. Transition to inside
    • The device and its accuracy radius are now completely enclosed in the geofence
  2. Transition to outside
    • The device and its accuracy radius are now completely outside in the geofence
  3. Boundary
    • The accuracy radius intersects with the geofence boundary.
The device is completely outside the geofence
Figure 1. The device is completely outside the geofence
The device position intersects the geofence
Figure 2. The device position intersects the geofence
Figure 3. The device position intersects the geofence
The device iscompletely inside the geofence