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Search Effort

Search Effort

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Search Effort

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  1. Search Effort

  2. The Balancing Act • Limited Resources • Planning Time in Search Area – how much time does it take to complete a search assignment?

  3. Time in Search Area • Sample air search problem: • Quarter Grid (in Central Minnesota) • 1 NM track spacing • 90 Knots Airspeed

  4. 45 30’ N 46 00’ N 94 00’ W 93 30’ W o o o o 30’ x 30’

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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)

  14. 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

  15. 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

  16. 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

  17. Search Time Equation: Track Spacing, S • The distance between searchers or legs of the search pattern

  18. 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)

  19. 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

  20. 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…