“Ana arrived home.” “Leo left school.” Alerts like these, which show up on your phone on their own, come from a technology called a geofence, or virtual fence. It’s used in family location apps, delivery apps, reminders and even fleet systems.
In this article you’ll learn what a geofence is, how your phone knows someone crossed it, which size to choose for each kind of place, what the real limitations are, and how to get the most out of it every day.
What a geofence is
A geofence is an area drawn on the map, usually a circle with a center and a radius. When a phone (or a tracker) enters that area, an entry event happens. When it leaves, an exit event. The app turns those events into alerts.
In practice, you only need to answer three questions:
- Where is the place? For example, home, school or work.
- How big is the area? The circle’s radius.
- Who do I want to hear about? Which people or devices trigger the alert.
On LeMoove, this is called place alerts: you mark the place, adjust the radius and choose whose arrivals and departures you want to be notified about.
How your phone knows someone entered or left
A phone estimates its position by combining several sources:
- GPS (and other satellite systems): the most precise source outdoors, usually accurate to a few meters under open sky.
- Nearby Wi-Fi networks: a big help in cities and inside buildings.
- Cell towers: less precise, but available almost everywhere.
Every position comes with a margin of error. Indoors, near tall buildings or in garages, that margin can exceed dozens of meters. That’s why a dot on the map sometimes appears slightly off, even when the person isn’t moving.
With those positions, the app compares: was the person outside the circle and now inside? Then there was an entry. To avoid false alerts when someone is right at the edge, good systems confirm the change before notifying instead of reacting to a single point. LeMoove does this confirmation so that GPS drift near the edge doesn’t turn into a string of “arrived, left, arrived”.
Which radius to choose for each kind of place
The radius is the most important decision. Too small causes false alarms, because GPS error “pushes” the person outside the circle. Too large makes the alert arrive too early or too late.
Some practical starting points you can fine-tune later:
| Kind of place | Suggested starting radius | Why |
|---|---|---|
| House or apartment | 200–300 m | Covers indoor GPS error without catching the whole neighborhood |
| School | 250–400 m | Schools take up blocks and have several entrances |
| Office building | 250–400 m | Tall buildings degrade GPS |
| Gated community or campus | 500 m–1 km | The area itself is large |
| Neighborhood or small town | 1–3 km | To know someone “got to the area” |
On LeMoove, the radius goes from 200 meters to 3 kilometers. The 200-meter minimum is deliberate: with smaller radiuses, normal GPS variation would trigger alerts for things that never happened.
Where virtual fences really help
- School arrivals and departures. One alert when your kid arrives in the morning and another when they leave.
- Older relatives. Knowing when someone leaves home at an unusual time.
- Coming home from work. Starting dinner when the “left work” alert comes in.
- Vehicles. With a GPS tracker, knowing when the car enters or leaves the garage.
- Pets. An alert if your pet goes past the gate, when they wear a collar tracker.
The limitations almost nobody mentions
Geofences are very useful, but they’re not magic. Knowing the limits helps you avoid frustration:
- Power saving delays alerts. Some phones, especially Android devices with aggressive battery optimization, suspend background apps. The alert can arrive a few minutes late.
- No internet, no alert (yet). The phone has to send its position to the server. Without mobile data or Wi-Fi, the alert only goes out when the connection comes back.
- “Always” permission matters. If location is only allowed “while using the app”, the phone won’t report its position with the app closed, and alerts fail.
- Passing by isn’t arriving. A simple fence alerts when someone crosses the area, even if they’re just passing through. In LeMoove’s next update, safe arrival fixes this: it only says someone arrived once they’ve stayed at the place for a few minutes.
How to create a virtual fence on LeMoove
- Open the app and go to your places.
- Tap to add a place, search the address or tap the map.
- Name it, like Home or School, and adjust the radius.
- Choose whose alerts you want at that place.
- Save. Arrival and departure alerts will start reaching your phone.
Arrival and departure alerts work on every plan, including Free, which allows 2 places. Basic allows 10, and Complete has no limit. See the details on the plans page.
Good practices
- Start with a few places. Home and school already cover most situations.
- Tune the radius after a few days. If false alerts show up, increase it a little.
- Choose carefully whose alerts you get. Alerts about everyone everywhere become tiring, and too many alerts make people ignore the important ones.
- Use quiet hours so you don’t get alerts in the middle of the night.
- Talk to the people you follow. They should know that the place alerts you when they arrive or leave.
Frequently asked questions
Does the person know a place alert exists?
They know they’re sharing their location, because they installed the app and allowed it. On LeMoove, places belong to whoever created them and aren’t shown to other group members. That’s why the places that exist should be part of the conversation.
Does it work without internet?
The position has to reach the server for the alert to go out. Without internet, the alert waits and is sent once the connection comes back.
Can I use geofences for vehicles and pets?
Yes, as long as they have a GPS tracker. The tracker sends its position by itself, and place entries and exits work the same way as for people.
How many places can I create?
On LeMoove, 2 on the Free plan, 10 on Basic and unlimited on Complete.
Why did I get a departure alert when the person didn’t leave?
The most common cause is a radius that’s too small in a place with poor signal, like a high-rise apartment or an office building. Increasing the radius a little usually fixes it.
In short
A geofence is a circle on the map that alerts you when someone enters or leaves. It depends on your phone’s accuracy, so the right radius and confirmed entries and exits make all the difference. With a few well-chosen places, a suitable radius and “Always” location permission, a virtual fence becomes one of the simplest ways to know everyone got there safely, without having to ask.
