PROBABILITY OF SEARCH AREA (POA)

 

(The probability that the subject is in a particular segment or location.)

 

·        Draw the search area on a map.

·        Segment the search area into workable sizes that can be searched in 4-6 hours (rule of thumb ≈ ¼ square mile).   Segments should have boundaries that are clearly identifiable in the field.

·        Prioritize each segment in the search area by assigning probabilities of area,.  (A proven method is to obtain a consensus from a group of planners.  Each person’s total must equal 100%.)  Always include the rest of the world (ROW) as a segment.

 

METHODS OF ESTABLISHING THE SEARCH AREA

 

  1. THEORETICAL:  Distance that the subject could have traveled in the time elapsed.  Theoretical Search Area = 3.14 X (travel distance)2

Refer to table for likely travel distances.

  1. STATISTICAL:  Data which reflects the distances other subjects have traveled given similar conditions.  Refer to actual cases.
  2. SUBJECTIVE:  Evaluation of the limiting factors that exist for the specific incident and geographical location.  Consider barriers to travel and travel aids in actual search area.
  3. REASONING:  Systematic analysis of circumstances surrounding the disappearance of the subject.  Put yourself into the missing subject’s place.  Where would you go?

 

 

SHIFTING POA:

 

After an area is searched, a new updated POA for the segment can be calculated:

 

POA¢ = ( 1 – PODcum ) x POAold

 

The sum of the calculated POA¢s will most likely not equal 100%.  However, since 100% is required, the values must be normalized.  This is done by dividing each segment POA¢ by the sum of the calculated POA¢s.

Segment    PODcum      POA’          POANEW

    1             60%           16%           32%

    2             85%             3%              6%

    3             90%             1%              2%

    4               0%            20%           40%

ROW                     0%            10%           20%

-------               -------

SUM =                           50%           100%

 

Search criteria can now be based on the new probabilities of area.