memory. Routes are often used when frequently traveling between two or more locations be cause it is a faster and more ac curate method th an repeatedly selecting individual waypoints e ach time one travels through the same area . Routes consist of a Start Waypoint,an End Waypoint, and a series of waypoints in between. Users can begin navigation at the beginning, the end (to runthe route in reverse) or at any waypoint in between. See Waypoint.

SD: SD is an a cronym for Se cure Digital. An SD ca rd is vi rtually identical in function to an MMC; however, the speed at whichinformation can be accessed is generally faster, the storage capacity is generally larger, and the card has security features which can be used to prevent extracting the data from the card. SD is the same format that many digital cameras use. See MMC.

Selective Availability: Selective Availability (SA) is a GPS system “feature” that can be i mplemented by the U.S. Department of Def ense (DoD) to degrade the accuracy of GPS positioning information. With SA active, the GPS is accurate to within 100 meters95% of the time. With AS inactive, the GPS is accurate to within 45 meters 95% of the time. Currently, SA is inactive and the consumer can enjoy the greater precision GPS provides; however, the DoD reserves the right to activate SA at any time.

Speed Over Ground (SOG): Speed Over Ground is the measurement of the boat’s progress across a given distance, and is thespeed measurement provided by GPS. An alternate, Speed Through Water, is provided by a speed paddlewheel, and is the measurement of the flow past the boat,which may vary dependingon current speed a nd direction. S peed Over G round is o ptimal f or navigation because accurate destination times can be derived from this measurement. Humminbird® products allow for input and display of bothspeed measurements.

Time ToGo (TTG):Time To Go is the estimated time required to eachr the destination waypoint. TTG is calculated using the SOG and DTG. See SOG and DTG.

Track: A Track is a series of saved points that define the past path of the boat. These TrackPointsare saved at regular timeintervals.Tracks are a useful and quick method to see where you’ve been, and an easy guide tofollow to get you back to the starting point. Generally, all GPS units have a limited number of Track Points that can be saved before the unit runs out of memory and begins erasing thefirst track points saved. Because of this, the user can adjust the Track Point Interval

Glossary

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