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Glossary GPS & Navigation Terms
137
Speed Over Ground (SOG): Speed Over Ground is the measurement of the
boat’s progress across a given distance, and is 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): Time To Go is the estimated time required to reach 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 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.
Track Line (TRK): The Track Line is the desired line of travel between two
waypoints, and represents the most efficient path between the two points
because it is a straight line. The TRK is measured in degrees (i.e. 321°, where
000° is North, 090° East, 180° is South, 270° is West). See Cross Track Error
and Course Over Ground.
Trackplotter: Trackplotter describes a navigation device that shows Present
Position, along with Track, Waypoint, and Routes, but NO MAP in the
background. See Chartplotter.
Trolling Grid: Trolling Grid is a Humminbird® feature that displays a precise
reference grid around a waypoint. This grid is used as a guide pattern for trolling
around a specific area to assure a more efficient and complete coverage of that
area. Trolling Grid resolution be changed by zooming in or out on the chart. The
Trolling Grid can also be rotated on the display to orient it for optimal boat course
for wave and wind conditions.
UTC: UTC is an acronym for Universal Time Constant. UTC is the “standard time”
used in navigation, and is the local time in Greenwich England. (UTC is
equivalent to Greenwich Mean Time (GMT)). To display the correct Local Time in
a Humminbird® GPS unit, the user must use the Local Time Zone menu and
select the time zone (i.e. EST, CST).
WAAS: WAAS is an acronym for Wide Area Augmentation System. WAAS is
complementary technology to GPS that provides enhanced accuracy through
correction signals broadcast from Federal Aviation Administration WAAS
satellites stationed over the USA. These secondary signals are automatically
received by the standard Humminbird® GPS Receiver. With WAAS signal, GPS
accuracy is improved to within 3 meters 95% of the time. Outside the United
States, regional governmental coalitions have created similar systems such as
EGNOS (Europe) and MSAS (Japan).