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

adjacent to it, are the following: aircraft radio call sign,
aircraft assigned search altitude, assigned track spacing,
type of pattern, and times required to fly t1, t2, and t3.
G. Air Plot/Relative Plot
1. General
a. Although a true plot may be used to plot and vector
the search aircraft during coordinated search patterns, an
easier method is to employ a relative motion pattern. The
relative motion pattern is laid out on the vessel air plot or
relative plot board, and is the primary source of information
for the advisories furnished the aircraft by the vessel during
the search.
b. The true plot, or surface plot, is laid out on the
vessel DRT in the vessel Combat Information Center (CIC). The
vessel relative plot or air plot board is close to the DRT.
This board is usually edge-lighted or back-lighted, has
permanently inscribed bearing lines and range circles similar
to a maneuvering board, and is used to plot aircraft targets
relative to vessel position.
2. Relative plot and true plot comparison
a. The vessel air controllers should thoroughly
understand the difference between the true plot and the
relative plot, as well as their relationship. The air
controller may have to rapidly shift from using the relative
plot to using the true plot if ship radar fails or radar
contact with the aircraft is lost.
b. With known values for ship course and speed, existing
wind direction and speed, length of searchlegs, and track
spacing, the relative motion pattern may be computed and laid
out by the vessel before the search aircraft arrives. The
shape of the relative motion pattern, when executing any of
the creeping line coordinated patterns, is similar to a
bowtie.
c. Figure E-3 illustrates the common-time relative
bearings of vessel and aircraft, and Figure E-4 is a
simplified form of Figure E-3, showing the relationship
between the true plot and relative plot patterns. Only four
common time positions are shown for the vessel and aircraft,
and aircraft turning diameter is ignored.
(1) The comparison is started with the aircraft in
position ahead of the vessel, at position 1. The
relative bearing of the aircraft from the vessel
stays constant until the aircraft
E-4