Humminbird 757c - Manual (Page 163)

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.
Estimated Position Error (EPE): Estimated Position Error is a calculation that
indicates the potential position inaccuracy the user may experience due to a
variety of GPS factors which include satellite position in the sky, signal strength
and others factors.
Fix Type: Fix Type indicates whether the GPS receiver is providing 2D fix or 3D fix. A
2D fix requires only three satellites and provides only latitude and longitude. A 3D fix
requires four or more satellites, and provides latitude, longitude and altitude.
GPS: GPS is an acronym for Global Positioning System. GPS provides accurate
position (latitude, longitude, altitude) information virtually anywhere on the earth
through satellite technology and personal receivers on the ground. A series of
geosynchronous satellites broadcast a unique signal toward the earth once per
second. A GPS receiver, such as that included with many Humminbird® products,
receives the signals from these satellites and is able to determine position based
on very slight differences in the time each signal is received and the receiver’s
knowledge of the location of each of the satellites.
Heading: Heading describes the direction the boat is pointing and is measured in
degrees (i.e. 321°, where 000° is North, 090° East, 180° is South, 270° is West).
Due to wind and waves, the boat is often traveling in a slightly different direction
than it is heading, and therefore Heading is often confused with Course Over
Ground. See Course Over Ground.
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