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Present Position The current location (latitude, longitude) determined by GPS. The
Present Position is indicated on-screen by a directional boat icon if the boat is moving or a
round symbol if the boat is stationary.
Route A series of waypoints linked together in a specific sequence to define a navigation
path between two points, and saved in the fishfinder’s memory. Routes are often used
when frequently traveling between two or more locations because it is a faster and more
accurate method than repeatedly selecting individual waypoints each 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 run the
route in reverse) or at any waypoint in between. See
Waypoint.
SD (Secure Digital) An SD card is virtually identical in function to an MMC; however,
the speed at which information 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 (SA) A GPS system “feature” that can be implemented by the U.S.
Department of Defense (DoD) to degrade the accuracy of GPS positioning information. With
SA active, the GPS is accurate to within 100 meters 95% of the time. With SA 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) The measurement of the boat’s progress across a given
distance and the speed 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 depending on current speed and direction. Speed Over Ground is optimal
for navigation because accurate destination times can be derived from this measurement.
Humminbird® products allow for input and display of both speed measurements.
Time To Go (TTG) The estimated time required to reach the destination waypoint. TTG is
calculated using the SOG and DTG. See
SOG and DTG.
Track A series of saved points that define the past path of the boat. These Track Points are
saved at regular time intervals. Tracks are a useful and quick method to see where you’ve
been, and an easy guide to follow 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 the first track points saved. Because of this, the user can adjust
the Track Point Interval menu to increase the amount of time between when points are
saved, and thus extend the distance covered by a track. Tracks can also be permanently
saved to memory and re-displayed at the user’s option.
Glossary - GPS & Navigation