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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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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
slide4

45 30’ N

46 00’ N

94 00’ W

93 30’ W

o

o

o

o

30’ x 30’

slide5

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

slide6

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

slide7

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

slide8

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

slide9

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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