Leica MX400 Operating Instructions Manual page 225

Operator's Manual
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 ex-
pressed as the radius of a circle around the calculated (dis-
played) 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.
UTM
See UNIVERSAL TRANSVERSE MERCATOR
UNIVERSAL TRANSVERSE MERCATOR
Alternative grid system used in harbor areas and for land
applications instead of latitude and longitude.
VDOP
An indicator of the accuracy in altitude. See DILUTION OF
POSITION.
VELOCITY MADE GOOD (VMG)
The speed by which the vessel is moving in the upwind direc-
tion. When tacking, the optimization should be based on VMG
(assuming that TWD is expected to be fairly constant). See also
WAYPOINT CLOSURE VELOCITY.
VISIBLE SATELLITE
A satellite whose orbit has placed it above the earth's horizon
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Glossary
Version 3.3