Inertial Navigation System (INS)
~ INS consists of accelerometers and rotational rate sensors
~ they provide frequent estimations of the helicopter’s position, velocity, orientation, and rate of rotation
~ although this estimate is provided at a high rate — roughly 100 Hz— the error in estimate could grow unbounded over time
~ this is due to sensor noise and limits in sensor accuracy

Global Positioning System (GPS)
~ GPS solves INS drift problem by providing a position measurement whose error is small —on the order of 1 cm— and bounded over time
~ however, this accurate measurement is also infrequent —roughly 5 Hz

Integrated INS-GPS solution
~ uses a Kalman filter to provide frequent updates of the estimated state of the helicopter
~ this Kalman filter is run by the flight computer, which also computes a control law and sends the result to the actuators