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

Search radius is defined as R1 for the first search, R2 for the second,
etc. R is computed by multiplying E by the appropriate fs, i.e., R = E
x fs.
523 Search Area Development
A. Theoretically, the best search area is a circle centered on
datum. However, few search patterns are adaptable to circular search
areas. For most patterns, a square or rectangular search area is more
The ends of the area are squared off with tangent lines as illustrated
in Figure 5-12. Figure 5-13, a datum line search expansion, shows
development of the next search area enlargement, assuming the datum line
is not stationary.practical. Circular areas are simply boxed in as
shown by Figure 5-10.
B. For a search with little or no drift, search area is
constructed around a stationary datum. If the target is not found, the
area may be expanded for subsequent searches. Therefore, the area
around datum, which continues to be the most probable location, is
searched repeatedly.
C. For maritime incidents, datum will normally move during the
search, as Figure 5-11 illustrates. The enlargement of the search area
for a moving datum is the same as for a stationary datum, but the area
is centered on a new datum so that the water surface is re-searched
where survivors are most likely to be.
D. A search area along a datum line is set up by first developing
a search radius for each datum along the trackline. Each datum is
circled, using its search radius. Tangent lines are then drawn from
circle to circle to establish search area boundaries.
Figure 5-10. Search Areas - Stationary Datum Point