A dual global positioning system (GPS) receiver navigation system. The system of the present invention includes a primary GPS receiver adapted to determine a first position. The primary GPS receiver is certified to a first integrity level and is further adapted to provide GPS navigation data to an external device. The system of the present invention also includes a secondary GPS receiver coupled to the primary GPS receiver. The secondary GPS receiver is certified to a second integrity level having less stringent requirements than the first integrity level. The secondary GPS receiver is adapted to determine a second position and monitor the primary GPS receiver to detect a fault condition by comparing the first position and the second position, such that the GPS navigation data is provided in accordance with the first certification level regardless of the second integrity level of the secondary GPS receiver.

A high integrity navigation system is created using a low integrity navigation computer monitored by a high integrity system. A navigation sensor (e.g. DGPS, GPS, ILS, MLS, and the like) is programmed with a desired trajectory. The navigation sensor calculates the vehicle position and generates a deviation signal indicative of the deviation of the vehicle from the desired trajectory. The navigation computer uses the deviation signal in the control law computations to generate steering commands for controlling the vehicle. The navigation sensor monitors the deviation of the vehicle from the desired trajectory. If the deviation exceeds a predetermined threshold, an integrity alarm signal is communicated to a display or other alarm to alert the operator.

A mobile device (MS) is disclosed comprising a GPS receiver (14) and an audible alarm (13, 15) configured to sound, during operation of the GPS receiver, in response to either adverse performance of the GPS receiver or to an event which is adverse or likely to be adverse to the performance of the GPS receiver. The alarm may sound in response to the inability of the GPS receiver to either acquire or track a GPS signal, or obtain or maintain a position fix. Also, the alarm may sound in response to movement of the GPS receiver, including acceleration and higher order movement of the GPS receiver, in so far as that movement is adverse to the performance of the GPS receiver.

A device for adjusting a parameter includes a selector that is actuated by an operator. A coder is driven in rotation by the actuation of the selector and emits a signal representative of the rotation. A first detector detects an actuation of the selector, and a second detector detects the emission of the signal indicating the change of the selected value. A comparitor, linked to the first and second detectors, determines a malfunction when only one of the first and second detectors makes a detection.

The present invention is a system for providing GPS users with a high level of confidence in the integrity and accuracy of received GPS signals. A waveform monitor allows the GPS satellite to verify the integrity of its transmitted signal by detecting its own transmitted waveform. The waveform monitor includes a receiver mounted in the GPS satellite. The receiver receives the GPS signal transmitted by the GPS satellite. The waveform monitor then compares the received GPS signal with a copy of what the GPS satellite intended to send which is stored in memory. The waveform monitor can compare the received digital navigation message with the copy stored in memory, and/or compare the received RF waveform with waveform data stored in memory. The waveform monitor thereby determines whether the transmitted signal has integrity. The GPS satellite then sends an integrity message to GPS users to inform the GPS users of the integrity of received GPS signals from that satellite.