GPSMAP 496 Owner’s Manual 163Appendix > Learning about GPSLearning About GPSThe Global Positioning System (GPS) is a satellite-based navigationsystem made up of a network of 24 satellites placed into orbit by theUnited States Department of Defense.GPS was originally intended for military applications, but in the1980s, the government made the system available for civilian use.GPS works in any weather conditions, anywhere in the world, 24hours a day. There are no subscription fees or setup charges to useGPS. For more information refer to the Garmin Web site atwww.garmin.com and also read the GPS Guide for Beginners atwww.garmin.com/aboutGPS/manual.html.Common GPS Termsinitialize—the first time a GPS receiver orients itself to its currentlocation and collects data. After the receiver is initialized, itremembers its location and acquires a location more quickly.Location—an exact, unique location based on geographiccoordinates (Latitude and Longitude).route—A group of waypoints entered into the GPS receiver in thesequence you want to navigate them.Waypoint—a location you store in your GPS.What is Differential GPS (DGPS)?The United States and Canadian governments (among others) haveset up Differential GPS (DGPS) stations to transmit correctionsignals. They are operational in coastal areas and on many navigableriver systems.The DGPS system is available for use without a fee, but you do needadditional equipment to receive DGPS signals: A beacon receivercompatible with the RTCM format sentences supported by yourGarmin GPS is needed to use DGPS.Refer to the United States Coast Guard’s Web site (www.navcen.uscg.gov) for locations and status of the differential stations.Differential FieldDifferential receiver status is indicated in the bottom-left field of theGPS Page and shows one of the following conditions:none—no optional beacon receiver is attached or enabledon the Interface sub tab on the Main Menu or WAAS isturned off.Searching for WaaS—WAAS is enabled and the receiver issearching for WAAS signal.Using WaaS—WAAS capability is enabled and the unit isreceiving WAAS corrections.•••
