Geofences
A geofence is a boundary the app watches for you. Cross it and your phone says so, which helps if you need to stay inside a work area, keep clear of a hazard, or know the moment you reach a site.
Three shapes
| Type | Defined by | Typical use |
|---|---|---|
| Circle | A centre and a radius (10–1 000 m) | A site, a well, a base station |
| Polygon | Three or more corners | A plot, a concession, a no-go area |
| Corridor | A line and a buffer width (10–1 000 m) | A road, a pipeline, a transect |
Creating and editing
Library › Geofences › Add Geofence opens the editor, which is a map with a panel you can pull up over it. Pick the type on the map toolbar, then place the shape by tapping the map, from your GPS position, from a GPS average, from the crosshair, or by pasting coordinates. Polygon corners and corridor points can be dragged. The hollow handle between two points adds a new one, and double-tapping a handle removes it. Undo and Reset are in the panel.
Under the geometry, choose whether to be alerted on entering, on leaving, or on both, and write the message for each if you want one. Tapping a geofence card in the list opens its options: edit, activate or deactivate, and delete.
Monitoring
Turn on Background Monitoring at the top of the Geofences tab. Tavak then keeps an eye on your position with the app in the background or the screen off, and puts up a notification as you enter or leave an active geofence.
- Monitoring needs location permission, plus notification permission on Android 13 and later. The app asks for both when you turn it on.
- Poor fixes are ignored, and a boundary has to be crossed by a small margin before anything changes, so standing near an edge will not set off a stream of alerts.
- Turning monitoring on while you are already inside a geofence does not count as entering it.
- Monitoring starts itself again after the phone restarts, as long as the switch was left on.
- You can turn it off at any time, even once every geofence has been deactivated or deleted.
Import and export
Geofences can be downloaded or shared as GeoPackage, Shapefile (as a ZIP) or GeoJSON, and imported from the same formats, whether they came from Tavak or from QGIS. A circle is exported as a point with a radius attribute, a corridor as a line with a buffer, and a polygon as a polygon. The enter and leave settings and their messages travel with them. Import a file you exported earlier and it recognises the geofences already on the device and leaves them alone.
A projected shapefile is transformed using its .prj. A radius outside the allowed range is pulled back to 10–1 000 m. One file can bring in up to 1 000 geofences.
When it doesn’t work
- The switch will not turn on
- The message underneath tells you which permission is missing: location, or notifications on Android 13 and later. Grant it in system settings and try again.
- No alert arrived
- Check that the geofence is active and that the trigger you want, entering or leaving, is switched on. Some phones stop background services under battery optimisation, so exclude Tavak from it.
- Alerts fire repeatedly at the edge
- You are standing within GPS error of the boundary. Move a few metres inside it. The margin copes with ordinary jitter, but not with standing on the line.