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Search Effort. The Balancing Act. Limited Resources Planning Time in Search Area – how much time does it take to complete a search assignment?. Time in Search Area. Sample air search problem: Quarter Grid (in Central Minnesota) 1 NM track spacing 90 Knots Airspeed. 45 30’ N. 46 00’ N.

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Search Effort

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Search effort

Search Effort


The balancing act

The Balancing Act

  • Limited Resources

  • Planning Time in Search Area – how much time does it take to complete a search assignment?


Time in search area

Time in Search Area

  • Sample air search problem:

    • Quarter Grid (in Central Minnesota)

    • 1 NM track spacing

    • 90 Knots Airspeed


Search effort

45 30’ N

46 00’ N

94 00’ W

93 30’ W

o

o

o

o

30’ x 30’


Search effort

15’ x 15’

15’ x 15’

15’ x 15’

15’ x 15’

93 45’

45 30’ N

46 00’ N

45 45’

94 00’ W

93 30’ W

o

o

o

o

o

o


Search effort

93 45’

45 45’

45 30’ N

46 00’ N

93 30’ W

94 00’ W

o

o

o

o

o

o

413

414

Twin

Cities

445

446


Search effort

7.5’

7.5’

414

7.5’

7.5’

445

446

45 45’

93 45’

45 30’ N

46 00’ N

94 00’ W

93 30’ W

o

o

o

o

o

o

Twin

Cities


Search effort

414

445

446

45 30’ N

46 00’ N

93 45’

45 45’

94 00’ W

93 30’ W

o

o

o

o

o

o

B

A

D

C

MSP

413


Search effort

414

445

446

45 30’ N

46 00’ N

93 45’

45 45’

94 00’ W

93 30’ W

o

o

o

o

o

o

B

A

D

C

MSP

413 A


Computing time in search area

Computing Time in Search Area

5.25 NM

1 “square” degree in Central Minnesota is about 60x42 NM, so a quarter grid is about 7.5 x 5.25 NM.

Quarter Grid:

MSP 413A

7.5 NM


Computing time in search area1

Quarter Grid:

MSP 413A

4.25 NM

1/2 NM

7.0 NM

1 NM

1 NM

1 NM

1 NM

1 NM

1 NM

1 NM

Computing Time in Search Area

We have 8 sweeps 4.25 NM long each plus 7 NM distance covered moving between sweeps.

That’s 8*4.25+7, or about 41 NM.

At 90 Kts, that is about a half hour.


Time in search area1

Time in Search Area

  • Typical sortie assignment is a half grid (two quarter grids)

  • Additional time is needed to travel to and from the search area

  • For missions, we restrict our flight time in C-172s (with standard tanks) to three hours


Search time equation

Search Time Equation

  • A = V*S*T*N

    • A, Area

    • V, Velocity

    • S, Spacing

    • T, Time

    • N, Number of Resources

  • This equation works for ground search too(think search lines)


Search time equation velocity v

Search Time Equation: Velocity, V

  • Search Speed of SRU

    • Not cruise speed

  • For Aircraft, 60-90 Kts

  • For Ground Teams, 0.25-0.30 MPH

    • 0.29 MPH typical

      • Based on studies of trained searchers in moderately dense trees and underbrush in the Pacific Northwest

      • works out to about 3.5 hours per mile


Search time equation time t

Search Time Equation: Time, T

  • Time spent actively advancing the pattern

  • Time Enroute to and from search area not included

  • Must discount time spent maneuvering and investigating sightings

  • Rule of thumb for aircraft:

    • T is 85% of time in search area

    • Less if complicated by lots of junk that needs to be investigated

  • May be bound by available daylight hours


Search time equation number of resources n

Search Time Equation:Number of Resources, N

  • Number of identical resources used

  • Examples:

    • Number of searchers in a ground team

    • Number of aircraft searching at the same airspeed for the same length of time


Search time equation track spacing s

Search Time Equation: Track Spacing, S

  • The distance between searchers or legs of the search pattern


Search time equation solving for other variables

Search Time Equation:Solving for Other Variables

  • Spacing Required

    S=A/(V*T*N)

  • Resources Required

    N=A/(V*S*T)

  • Time Required

    T=A/(V*S*N)

    (We don’t generally try to solve for V)


Search time equation recap

Search Time Equation Recap

Our Example One Last Time: A Quarter Grid in Central MN is 7.5 x 5.25 NM or about 40 NM2

  • T = A / ( V * S * N ) [from previous slide]

  • T = 40 NM2 / ( 90 NM/hr * 1NM * 1)

  • T = 4/9 hr  0.44 hr

  • But this doesn’t account for maneuvering (turning onto new legs of search pattern)

    • So, divide by 0.85, the rule of thumb, and we get 0.52 hr

    • This estimate assumes little time spent investigating sightings


The balancing act revisited the poa pod trade off

The Balancing Act Revisited:The POA – POD Trade-Off

  • Requirements for Successful Search:

    • You must be searching where the person is

      • POA is the likelihood you are in the right place

    • You must be able to detect the person

      • POD is the likelihood you can detect the person

  • Your goal: search an area large enough to likely contain the person but small enough so that your searchers will be closely enough spaced to likely detect the person

  • An obvious conflict…


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