EKF FAILSAFES
Critical safety mechanisms. Understanding Extended Kalman Filter variance, lane switching, and emergency behaviors.
Safety Mechanisms
Compass Fusion & Magnetic Interference
Magnetometers (Compasses) are the most fragile sensors on a drone. They are easily corrupted by power lines, metal bridges, or even the drone's own...
EKF Lane Switching & Redundancy
Modern [flight controllers](/field-manual/build-guide/flight-controllers.html) (like the Cube Orange) have multiple redundant IMUs (Accelerometers/...
EKF Variance & Innovations
When the GCS screams **"EKF Variance"** or **"Velocity Variance"**, it means the autopilot is confused. Specifically, it means the sensor data (GPS...
GPS Glitch Protection
GPS is imperfect. Multipath errors (signals bouncing off buildings) can cause the GPS reported position to jump 10 meters instantly. If the [flight...
Optical Flow Fusion
Optical Flow is the primary method for non-GPS [navigation](/field-manual/navigation-mission/navigation-architecture.html) (FlowHold) and precision...
Terrain Estimation (EKF)
For precision landing and [optical flow](/field-manual/ekf-failsafes/optical-flow-fusion.html), the drone must know its height above the ground (AG...
The Crash Checker
The **Crash Check** is a software safety mechanism designed to detect if the vehicle is out of control and impacting the ground. If a crash is conf...
The EKF Core: Fusion Architecture
The **Extended Kalman [Filter](/field-manual/advanced-tuning/harmonic-notch-filtering.html) (EKF)** is the mathematical brain of the autopilot. Its...
Vibration Failsafe & Clipping
Vibration is the #1 enemy of the EKF. If the frame vibrates too much, the accelerometers produce "Aliased" data—high-frequency shaking that the E...
Wind Estimation & Drag Fusion
Knowing the wind speed is critical for accurate [navigation](/field-manual/navigation-mission/navigation-architecture.html), especially for Return-...