Glossary
GPS & Navigation Terms
24
Acquisition Time:
The length of time that a GPS receiver typically takes to
determine a position from at least three satellites. Humminbird
®
GPS
receivers provide very fast acquisition times (under one minute), permitting
users to get out on the water faster.
Alarm, Arrival:
The audible alert that sounds when the boat is equal to or less
than the alarm setting (25 feet – 3000 feet) from the location of the destination
waypoint.
Alarm, Drift:
Drift Alarm is an audible alert that sounds when the boat is equal
to or over the alarm setting (25 feet – 3000 feet) from the location where the
alarm was turned on.
Alarm, Off-Course:
Off-Course Alarm is an audible alert that sounds when the
boat’s distance from the intended Track, (Cross Track Error), is equal to or over
the alarm setting (25 feet – 3000 feet). See
Track
and
Cross Track Error
.
Altitude:
Altitude measures height above sea level. Altitude is a measurement
that can be provided by GPS.
Bearing (BRG):
Bearing is the direction to a destination waypoint measured in
degrees from North (i.e. 321°, where 000° is North, 090° East, 180° is South,
270° is West).
Chartplotter:
Chartplotter describes a navigation device that shows Present
Position on a Map, along with Tracks, Waypoints, and Routes. All Chartplotters
are also considered Trackplotters. All Humminbird
®
GPS Combo units are
Chartplotters. See
Trackplotter
.
Cold Start:
Cold Start refers to the procedure that a GPS receiver must perform
when it does not have historical information regarding its current location. This
procedure typically lasts for several minutes, and may be experienced upon first
power up of the receiver, or if the receiver has been moved a great distance.
Course Over Ground (COG):
Course Over Ground is the current direction the
boat is traveling measured in degrees from North (i.e. 321°, where 000° is North,
090° East, 180° is South, 270° is West). When the Course Over Ground is equal
to Bearing, the boat is said to be “On Course” and will arrive at the destination
in the most efficient manner. COG is often confused with Heading. See
Heading
.
Cross Track Error (XTE):
Cross Track Error is the straight-line distance of the boat
from the intended Track. XTE measures how far the boat is off course, and also
triggers the Off Course Alarm. See
Track
.
Differential GPS (DGPS):
Differential GPS is a system to improve the position
accuracy of the Department of Defense GPS through the use of secondary
“correction signals” broadcast from ground stations around the coastal United
States and on some inland waterways. These correction signals are provided by
the USCG and received by an auxiliary Differential Beacon Receiver (DBR) that
connects to the GPS receiver. The advent of WAAS has largely negated the need
for the added expense of a DBR in the United States.
Distance To Go:
Distance To Go is the straight-line distance between Present
Position and the Destination Waypoint. DTG and SOG (Speed Over Ground) are
used to calculate Time To Go. See
Time to Go
and
Speed Over Ground
.
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