When creating a geofence, it should be noted that the GRETA does not always have an optimal view of the existing GPS satellites, e.g. inside a building.
In this case, the position is estimated as best as possible, taking into account the existing data. Since it may well happen that the displayed position deviates by several meters.
To avoid false alarms being triggered later, the area covered by the geofence should be large enough.
If a tracker has a small interval, the system waits up to three confirmation positions to make sure that the tracker is really out of geo-fence.
Further information can also be found in the section Positioning.