Geofences
A geofence is a virtual boundary that the flight controller enforces. If the drone approaches or crosses the boundary, the FC takes a configured action (RTL, land, report only, or brake).Fence Types
| Type | Shape | Description |
|---|---|---|
| Inclusion polygon | Polygon | The drone must stay inside this area |
| Exclusion polygon | Polygon | The drone must stay outside this area |
| Inclusion circle | Circle | Circular inclusion boundary |
| Exclusion circle | Circle | Circular exclusion boundary |
| Altitude fence | (none) | Maximum altitude limit (configured in FC parameters) |
Creating a Geofence
Draw the boundary
Click on the map to place vertices of the polygon. Double-click to close the polygon. For a circle, click the center and drag to set the radius.
Set the type
Choose inclusion or exclusion. Inclusion fences define where the drone CAN fly. Exclusion fences define no-fly zones.
Configure the action
The breach action is configured in the FC’s failsafe parameters (see FC Configuration). Common actions:
- Report Only: Log the breach but take no action
- RTL: Return to launch
- Land: Land immediately
- Brake: Stop and hover (copter only)
Editing Fences
After creating a fence:- Drag vertices to reshape the polygon
- Add vertices by clicking on an edge
- Delete vertices by right-clicking a vertex
- Delete the entire fence from the fence list
Downloading Fences
Click “Download Fence” to read the currently stored fence from the flight controller. This is useful when a fence was uploaded from another GCS.Rally Points
Rally points are pre-defined landing positions for emergencies. When the drone triggers an RTL failsafe (low battery, lost link, geofence breach), the FC can fly to the nearest rally point instead of the home position.Why Use Rally Points?
- Home position might be obstructed (crowd, vehicle, obstacle)
- Closer landing options exist in different directions
- Wind direction makes certain landing spots safer
- Multiple takeoff/landing areas in a large field
Creating Rally Points
Click the map to place points
Each click adds a rally point at that location. Add as many as you need.
Set altitude
Each rally point has a loiter altitude. The drone will loiter at this altitude above the rally point before landing.
Editing Rally Points
- Drag a rally point marker to reposition it
- Click a rally point to edit its altitude
- Right-click to delete a rally point
- Download existing rally points from the FC
How the FC Uses Rally Points
When RTL is triggered:- The FC checks if any rally points are stored.
- If rally points exist, the drone flies to the nearest one (by straight-line distance).
- The drone loiters at the rally point’s configured altitude.
- Depending on FC settings, it either loiters indefinitely or lands automatically.
Rally point behavior depends on the ArduPilot
RALLY_LIMIT_KM parameter. Points beyond this distance from the home position are ignored. Set this parameter to cover your entire operating area.Fence + Rally Combined
A common setup:- One large inclusion polygon defining the entire safe flight area
- Exclusion polygons around buildings, roads, or people
- 3-4 rally points at safe, clear landing areas within the inclusion zone
- Altitude fence set in the FC parameters as a ceiling
Upload and Download
| Action | Protocol | Description |
|---|---|---|
| Upload Fence | MISSION_ITEM_INT (MAV_CMD_NAV_FENCE_*) | Send fence items to the FC |
| Download Fence | MISSION_REQUEST_INT | Read fence items from the FC |
| Upload Rally | MISSION_ITEM_INT (MAV_CMD_NAV_RALLY_POINT) | Send rally points to the FC |
| Download Rally | MISSION_REQUEST_INT | Read rally points from the FC |
| Clear Fence | MISSION_CLEAR_ALL (fence type) | Remove all fence items |
| Clear Rally | MISSION_CLEAR_ALL (rally type) | Remove all rally points |