Attitude estimation is the process of determining the orientation of a rigid body, typically expressed as roll, pitch and yaw or as a quaternion, relative to a reference frame. It fuses measurements from an inertial measurement unit’s gyroscopes, accelerometers and magnetometers using sensor-fusion algorithms such as complementary or Kalman filters to counteract individual sensor drift and noise. Accurate attitude estimation is a prerequisite for stable flight control, robot balancing and any system that must reason about its own orientation in space.