Guides
What Is Geofencing? How Arrival and Leave Alerts Work
Geofencing draws an invisible circle around a place and alerts you when a phone enters or leaves it. How it works, how accurate it is, and how to set it up.
By NextLocator Team Updated 3 minute read
Quick answer
Geofencing is a virtual boundary, usually a circle drawn around a place like home or school. When a phone crosses that boundary, an app sends an alert, such as “Jim arrived at School”. It uses the same location data as a live map, so it needs location permission and an internet connection.
Key takeaways
- A geofence is a circle with a center point and a radius.
- Crossing into the circle triggers an arrival alert; crossing out triggers a leave alert.
- GPS drift near the edge can cause false alerts, so good apps add a small margin before counting a leave.
- In NextLocator, geofences are called places, and each circle can save several.
What is a geofence?
A geofence is an area on a map that an app watches. For family safety it is almost always a circle: a center point, like your front gate, and a radius, the distance from that point to the edge of the circle.
NextLocator calls these places. You choose the radius when you save one.
How are arrival and leave alerts triggered?
- You save a place with a name, an icon and a radius.
- A family member's phone sends its location as usual.
- NextLocator works out whether that location is inside or outside the place.
- If the member was outside and is now inside, that's an arrival. If they were inside and are now outside, that's a leave.
- NextLocator sends a notification to the circle's admins, and the event appears in the app for the circle.
Why can geofence alerts be late or wrong?
- GPS drift. A phone standing still can appear to wander by tens of meters, especially indoors. Near the edge of a small place, that can look like leaving and arriving again.
- Tall buildings and basements. Weaker signals make positions less accurate.
- Sleeping phones. If battery settings stop the app, no location arrives, so no alert can be sent.
- No internet. An alert can't reach your family until the phone reconnects.
To reduce false leave alerts, NextLocator waits until a member is a little beyond the edge before it counts them as having left.
How big should a place's radius be?
- Cover the whole building and its gate, not just the room your child is in.
- Use a larger radius for big campuses, hospitals and markets.
- Keep neighbouring places, like home and a relative's flat on the same street, from overlapping too much.
- If you get false leave alerts, make the radius larger.
Everyday uses for place alerts
- Knowing children reached school and coaching.
- Knowing a parent got home after a late shift at the office.
- Checking that grandparents arrived at the clinic or hospital for an appointment.
- Getting a heads-up that a family member left for home, so dinner is ready.
Read our guide to keeping kids safe on the way to school and coaching.
How to set up place alerts in NextLocator
- Open your circle and go to Places.
- Tap Add place.
- Move the map to the spot you want, such as the school gate.
- Give the place a name and choose an icon, such as Home, School, Office or Hospital.
- Set the radius and save the place.
How many places you can save depends on your plan. The setup guide walks through this with the rest of NextLocator.
Frequently asked questions
Is geofencing the same as location tracking?
Geofencing uses location tracking, but instead of showing where someone is all the time, it tells you when they cross the boundary of a place you care about.
Does geofencing work without internet?
Not reliably. Alerts need an internet connection to reach your family, so if the phone is offline when it arrives or leaves, the alert may be late or missed.
Why did I get a leave alert when nobody left?
GPS drift near the edge of a place can make a phone that is standing still look like it moved outside. Make the place's radius larger to stop it.
Who gets place alerts in NextLocator?
Arrival and leave notifications go to the circle's admins, and everyone in the circle can see the event in the app. The person who arrived or left doesn't get a notification about themselves.