NAVSTAR: The name given to GPS satellitesformed from the acronym for NAVigation Systemwith Time And Ranging.Non-Directional Beacon (NDB): A lowfrequency/medium frequency navigation aidsending non-directional signals that can be used fornavigation.O OBS: Omni-Bearing Selector.P Parallel Track Offset: A course that is parallel tothe designated course, but offset to the right or leftby a given distance.PDOP: Position Dilution of Precision. See Dilutionof Precision.R Radial: Any of the 360 magnetic courses from aVOR or similar navigational aid, beginning at thenavigational aid and proceeding outward in astraight line.RAIM: Receiver Autonomous IntegrityMonitoring. A method of predicting possiblesystem accuracy errors that may be caused by badsatellite data. The RAIM algorithm requires thatmore satellites are available and usable thanrequired for a normal GPS position fix.Range (RNG): The distance from the presentposition to a destination waypoint.S Second: 1/60th of a minute of a degree.Seed Position: A latitude and longitude position fixapproximately equal to the current position that theApollo SL50/60 uses to determine the location ofavailable satellites from which signals may bereceived.116Glossary of Navigation Terms
