Appendix I, Continued
DEPTH-SOUNDING SONAR.A direct-
reading device for determining the depth of
water in fathoms or other units by
reflecting sonic or ultrasonic waves from
the ocean bottom.
DEVIATION.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.
DEW POINT.he temperature to which
air must be cooled at constant pressure and
constant water vapor content to reach
DIP.Lowering a flag part way in salute
or in answer and hoisting it again. A flag
is "at the dip" when it is flown at about
two-thirds the height of the halyards.
DIRECTION OF RELATIVE
MOVEMENT.The direction of motion
relative to a reference point, itself usually
DIURNAL.Having a period of, occurring
in, or related to a day.
DIVIDERS.An instrument consisting in
its simple form of two pointed legs joined
by a pivot and used principally for
measuring distances or coordinates.
DOPPLER.The observed change of
frequency of a wave caused by a time rate
of change of the effective distance traveled
by the wave between the source and the
point of observation.
DRESSING LINES.The lines used in
DRESSING SHIP.A display of national
colors at all mastheads and the flagstaff.
(Full dressing ship requires, in addition, a
rainbow of flags from bow to stem over
DRIFT.The leeway of a vessel or
amount of set of a tide or current; the
spare end of a rope.
EBB.Tidal current moving away from
land or down a tidal stream.
magnetic and electric properties.
NAVIGATION.Navigation by means of
EQUATOR.The primary great circle of
Earth, or a similar body, perpendicular to
the polar axis.
ESTIMATED POSITION.The most
probable position of a craft determined
from incomplete data or data of
upon a scale in which, under standard
atmospheric pressure, water freezes at 32°
and boils at 212°.
FATHOM.A unit of length equal to 6