The system accommodates aircraft positioning using the GPS sensors. When power is applied to the system, each sensor is enabled. Each sensor is continuously monitored and compared by the system, ensuring the most accurate source is in use. When a sensor is in use, ‘Used’ will be its displayed status. See the GPS Receiver Operation in the System Overview Section for details on SBAS, sensor receiver information, and RAIM prediction.

Information on sensor failure and FMS degradation is discussed later in this section. Approach downgrade information is discussed previously in the Procedures portion of this section.