GPS signals. See also GPS LOG.
TRUE HEADING
Direction in relation to true north. True heading is com-
pass heading corrected for MAGNETIC DEVIATION and
VARIATION. The true heading used by the navigator for
navigation calculations is a composite of magnetic head-
ing input from the NMEA compass, magnetic variation as
calculated by the navigator, and the values entered into
the compass deviation table.
TRUE NORTH
Direction along the meridian of the observer to the north
pole.
TRUE WIND ANGLE (TWA)
Similar to APPARENT WIND ANGLE, but compensated for
the motion of the vessel. TWA and AWA are equal if the
vessel is not moving.
TRUE WIND DIRECTION (TWD)
The direction of the wind over ground, expressed as an
angular distance from north clockwise through 360°.
TRUE WIND SPEED (TWS)
The wind speed relative to either ground or water rather
than to the moving vessel.
UNCERTAINTY
In the navigator, an indication of the expected accuracy
expressed as the radius of a circle around the calculated
(displayed) position. The uncertainty is expressed in
meters or feet. The calculation of uncertainty is based on
the HDOP value.
UNIVERSAL TIME COORDINATED (UTC)
Greenwich mean time corrected for polar motion of the
Earth and seasonal variation in the Earth’s rotation.
UPDATE
See POSITION UPDATE.
UTC
See UNIVERSAL TIME COORDINATED.
To Next Page
Loading...
