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

1. Scale 1:24,000 is the best for land searches as it shows the
most detail. This chart reduces 2,000 feet of horizontal
topography to 1 inch. Each chart covers 7.5 minutes of
latitude and longitude.
2. Scale 1:62,500 reduces 1 mile of horizontal topography to 1
inch. Each chart covers 15 minutes of latitude and longitude.
3. Scale 1:125,000 reduces 2 miles of horizontal topography to 1
inch. Each chart covers 30 minutes of latitude and longitude.
4. Scale 1:250,000 reduces 4 miles of horizontal topography to 1
inch. Each chart covers 60 minutes of latitude and 120
minutes of longitude. This scale is useful when a large view
of the search area and surrounding terrain is desired.
Topographical charts may use any of four coordinate systems:
latitude and longitude, Universal Transverse Mercator (UTM) grid, state
plane, or rectangular surveys. When reporting the positions of finds,
the latitude and longitude should be used if known, supported by, if
possible, a bearing and distance from a prominent geographical feature.
C. Search Area Plot
1. The search area should be plotted on a topographical chart,
showing all search area and sweep boundaries. Two adjacent
sides are designated as baselines, each running from a common
corner point.
2. On a sheet of paper of suitable size, an area, sized in
proportion to the search area depicted on the topographical
chart, should be drawn. Each side of the expanded search area
should be marked with a scale, for every tenth of a mile,
creating a grid system.
3. The grid lines should be numbered in two directions, starting
from zero at a convenient corner. Each grid can be identified
by referring first to a vertical grid line number, then to a
horizontal grid line number. Furthermore, found objects can
be referred to by fractional estimates of the grid line number
at their locations. Grid lines are numbered only for
convenience of the team leader. Positions of found objects
are always converted to latitude and longitude for reporting
to the OSC, IC or SMC.
4. The gridded, large-scale plot of the search area is now ready
for depiction of each search sweep and any findings. To
determine search sweep boundaries, track spacing should be
estimated by the team leader. The track spacing is then
multiplied by the number of team searchers to obtain the full
width of the area searched on each search leg. This is then
measured on the search area plot, using double lines to
indicate boundaries and arrows for direction of each sweep.