JP 3-50 National Search and Rescue Manual Vol I - US Navy

3. Ratio of sweep width to track spacing (C = W/S).
Coverage Factor, Mean (Cm): The average of all coverage factors. Used
to obtain Cumulative Probability of Detection.
Craft: Any vessel, submersible, or aircraft of any kind and size.
Cumulative Probability of Detection: The likelihood of finding a target
as determined from the mean coverage factor together with the
appropriate curve for the number of searches.
Datum: The most probable location of the search object, corrected for
movement over time.
Datum Area: Area in which the search object is initially assumed to be
located with equal likelihood throughout the area.
Datum Line: Line connecting two or more datum points computed for the
same specified time, along which the search object is assumed to be
located with equal likelihood.
Datum Marker Buoy (DMB): Droppable floating beacon used to determine
actual sea current, or to serve as a location reference.
Datum Minimax: Datum point established midway between the resultant
minimum drift position (dmin) and the resultant maximum drift position
(dmax).
Dead Reckoning (DR): Determination of position by advancing a previous
position for courses and distances.
DETRESFA: ICAO equivalent to Distress phase.
Digital Selective Calling (DSC): System primarily used in GMDSS for
transmitting distress alerts from ships and associated acknowledgements
from coast stations, and for relaying alerts from ships or coast
stations.
Direction of Current: Direction toward which a current is flowing. Also
see set.
Direction of Waves, Swells, or Seas: Direction from which the waves,
swells, or seas are moving.
Direction of Wind: Direction from which the wind is blowing.
Disabled: Term describing a surface craft that has lost propulsion or
steering and needs assistance.
Distress Alarm: Alarm confirmed to be for an actual distress situation.
Distress Alarm Rate: Ratio of distress alarms to beacon alarms.