Page 44 951/952 Operator’s Manual Rev. BChapter 4 - Using ChartsYou may be able to use the displayed boundary lines to pre-dict when this change in detail is about to happen.Occasionally, you may see an hourglass symbol displayedbriefly in the information window on the screen while thechart is changing or being redrawn.Understanding nav aidsThe nav aids found on the unit’s electronic charts are repre-sentations of a variety of common “aids to navigation” usedthroughout U.S. coastal and inland waterways. Most of theseaids to navigation consist of buoys, lights, lighthouses, anddaybeacons, and typically are maintained by the U.S. CoastGuard. The purpose of nav aids is to warn mariners of hiddendangers—such as underwater hazards—and to enable them tosafely navigate specific waterways and channels.Buoys In the 951, nav aids are typically illustrated on the CHARTscreen as black circles with white letters. The most commonnav aids depicted on the charts are buoys. Those illustrated bya letter “G” represent green channel-marker buoys; a letter “R”indicates a red channel-marker buoy, “W” indicates white; and“Y” is for yellow. Approach buoys are shown as circles withblack on the upper half and white on the lower half. In the952, green, red, white, and yellow buoys are represented bythose actual colors (except when the 952 display is set fornighttime viewing, which uses either black or magenta colors).CAUTION!The unit’s nav-aid data has been manually converted from offi-cial paper charts to the electronic format on your screen and is,therefore, not necessarily as accurate as the source charts. Anaverage of 95 percent accuracy should be expected in the tran-sition from paper to electronic format. In some areas, only themost important nav aids may be shown.
