GPS Based Navigation Accuracy Question

[Chart8R]

RAT 5 Questions

• The problems with GPS in Italy used to be interference from television signals. I thought that had been sorted out now but I will watch the Notams.

• The RNP value associated with a nav fit has an accuracy, integrity, continuity and availabilityrequirement. The GPS element of that nav fit has a receiver with additional channels which are used for monitoring the integrity of the signals. This is known as GPS Receiver Autonomous Integrity Monitoring (RAIM). Any jamming or selective availability imposed on the GPS would be detected as an increase in the dilution of precision (the cocked hat gets bigger) and a RAIM failure. ICAO specifications for RNP receivers require pilot alerting of inadequate navigation performance whenever actual performance is worse than RNP.

A good review of FMS integrated navigation can be found at http://adsb.tc.faa.gov/WG4_Meetings/ASAS10%202005-July/STP%20appendix%20B_08-05-2005%20AWW.pdf
Cheers Chart8R