Prime Meridian - Correct Answer The 0 degree meridian of longitude, used as the
origin for measurement of longitude. The meridian of Greenwich, England, is almost
universally used for this purpose.
Charts - Correct Answer a map intended primarily for navigational use by aircraft or
vessels.
Sailing directions or pilots - Correct Answer A descriptive book for the use of mariners
containing detailed information of coastal waters, harbor facilities, etc. of an area. For
waters of the US and its possessions, they are published by the National Ocean Survey
and are called UNITED STATES COAST PILOTS. Sailing directions, as well as light
lists, provide the information that cannot be shown graphically on the nautical chart and
that is not readily available elsewhere. see also UNITED STATES COAST PILOT.
compass - Correct Answer An instrumental for indicating a horizontal reference
direction relative to the earth.
variation - Correct Answer The angle between the magnetic and geographic meridians
at any place, expressed in degrees and minutes east or west to indicate the direction of
magnetic north from true north. The angle between magnetic and grid meridians is
called GRID MAGNETIC ANGLE, GRID VARIATION, or GRIVATION. Called possible
ambiguity. Also called MAGNETIC DECLINATION. Change or difference from a given
value.
Deviation - Correct Answer The angle between the magnetic meridian and the axis of
a compass card, expressed in degrees east or west to indicate the direction in which the
northern end of the compass card is offset from magnetic north.
gyrocompass - Correct Answer A compass having one or more gyroscopes as the
directive element, and which is north-seeking. Its operation depends upon four natural
phenomena, namely gyroscopic inertia, gyroscopic precession, the earth's rotation, and
gravity. When such a compass controls remote gyrocompass.
log - Correct Answer An instrument for measuring the speed or distance or both
traveled by a vessel.
knot - Correct Answer A unit of speed equal to 1 nautical mile per hour
metric system - Correct Answer A decimal system of weights and measures based on
the meter as the unit of length and the kilogram as a unit mass.
nautical mile - Correct Answer A unit of distance used principally in navigation. the
length of 1 minute of any great circle of the earth.