Chapter 3 - Using the ControlsPage 3-2 961 Operations and Reference Manual Rev. DMore navigation terminologySome users who are new to navigation may find unfamiliarterms in this chapter; these terms have a special meaningthroughout the manual. Highlight Two defines several naviga-tion expressions with which experienced navigators mayalready be familiar.Highlight Two: More navigation termsARCS: Admiralty Raster Chart Service. The elec-tronic chart service designed by the United King-dom Hydrographic Office (UKHO).Course line: A line of travel from your present posi-tion to your upcoming (active) waypoint.Differential GPS (DGPS): A U.S. Coast Guard(USCG)-developed system of GPS corrections thatfurther increases position accuracy (requires aDGPS receiver). For more information, see Section2, ”Introducing GPS and DGPS,” starting on page2-13.Hydrographic Chart Raster Format (HCRF): Achart format designed by the United KingdomHydrographic Office, and used by ARCS (seeARCS definition above).Leg: The line, or path, between two waypoints in aroute or a trip.Nav aid: Aids to navigation often used oncoastal and inland waters. Nav aids primarilycomprise buoys, lighthouses, and daymarkers,and their purpose is to warn you of such hiddendangers as underwater hazards, and to helpyou safely navigate through specific waterwaysand channels.Trip: A sequence of waypoints comprisingtoday’s journey—a record of waypoints (includ-ing past, active, and future ones), coordinates,and routes. The trip function provides a way tocheck your actual progress, as well as makechanges, while you travel. On the CHARTscreen, the 961 color-codes your trip accordingto its legs: the past leg of the trip is displayed inyellow; the course line to the active waypoint isdisplayed in green; and future trip legs are dis-played in light blue.
