What is a lever arm in an integrated navigation system and how is it accounted for?

• A. The physical offset between the GNSS antenna and the INS reference point; accounted for in the measurement model and state.
• B. The manual lever used to stabilize hardware.
• C. The lever arm refers to a torque parameter in motor control.
• D. The lever arm is the distance from the GPS receiver to the satellite.

Answer: (A)

In an integrated navigation system, the lever arm is the fixed physical offset between where the GNSS antenna measures position and the INS reference point (often the IMU’s origin) on the vehicle. Since GNSS gives the position of the antenna and the INS tracks the body-frame origin, you must compensate for this offset to fuse the measurements correctly.

This compensation is done in the measurement model by incorporating the lever-arm vector, rotated into the navigation frame using the current attitude. Practically, the predicted GNSS measurement is the INS position plus the rotated lever-arm (and, for velocity, the additional term from the cross product of angular rate with the lever-arm if rotation effects are included). The lever arm can be treated as a known constant or estimated as part of the state and updated over time.

The other options aren’t describing this fixed, spatial offset between sensor locations, nor the way it’s used to align measurements from different sensors.