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Version 2.0
Operator’s Manual
Glossary
COURSE
The horizontal direction in which a vessel is steered or intended to
be steered, expressed as angular distance from north clockwise
through 360°. (Strictly the term applies to direction through the
water, not the direction intended to be made good over the ground).
The course is often designated as
true
,
magnetic
, or
compass
as
the reference direction is true, magnetic, or compass, respectively.
COURSE LINE
A line, as drawn on a chart, extending in the direction of a course
(Rhumb Line).
COURSE OVER GROUND
Course made good relative to the sea bed.
CROSS TRACK ERROR (XTE)
The perpendicular distance from the vessel to the actual course
line (track) as defined in the active route.
CURSOR
A flashing rectangle superimposed on a character position in the
display window, indicating that a character may be entered in that
position, or that the existing character may be changed via the
keyboard.
DATUM
The framework on which the coordinates used to define position
on the Earth’s surface are based. In the navigator, a datum is de-
fined by the following parameters:
A and I/F. Size and shape of a reference ellipsoid.
DX, DY, DZ. Position of the reference ellipsoid origin in relation to
the satellite datum ellipsoid origin.
DEAD RECKONING
The process of determining changes of position based on mea-
sured speed and course over measured time periods.
DECCA LINES OF POSITION (LOPs)
The phantom Decca Lines of Position used in the navigator are
based on mathematical models. Local deviations in propagation
Summary of Contents for MX420
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