Coast Guard Search

1
Coast Guard Search Rescue Metrics and
Definitions
Presented by Dave Larson
Slides 2-6 Courtesy of R.J. Koester, D.C.
Cooper, J.R. Frost, R.Q. Robe
2
Effective Sweep Width (Koopman)

• Cannot be measured directly
• Is an objective measure of detectability
• Large value gt detection is easy
• Small value gt detection is hard
• Depends on the characteristics of
• Searcher/Sensor (What we are searching with.)
• Search Object (What we are searching for.)
• Environment (What we are searching in.)
• Terrain, Vegetation, Weather, etc.
• Has units of length (feet, meters, miles, etc.)

3
A Uniform Random Distribution

4
Effective Sweep Width
(Unrealistic Perfect Detection Making a Clean
Sweep)

Number detected 40. Number missed within sweep
width 0. Number detected outside sweep width
0.
5
Effective Sweep Width
(More Typical Detection Pattern)

Number detected 40. Number missed within sweep
width 16. Number detected outside sweep width
16.
6
Effective Sweep Width Notes

• In both of the previous examples, there were
• The same object density ( of objects/unit of
  area),
• The same length of searcher track, and
• The same number of objects detected (40)
• Therefore,
• The effective sweep widths are also the same.
• Effective means has the same effect as
• Effective sweep width represents the expected
• amount of detection.

7

• Distance to right or left of sensor at the
  closest point of approach (CPA) is Lateral Range
• Lateral range curve (Koopman) Pd vs. Lateral
  Range

8
Effective Sweep Width

• Key to Improved Search Planning and Evaluation
• Improves POD Estimation
• Allows us to Objectively Relate POD to Effort
  Expenditure
• Has both Predictive and Retrospective Value
• More Accurate and Reliable than Subjective
  Estimates
• Based on Observable Factors
• Improves Effort Allocation
• Makes known, proven (mathematical) techniques
  available
• Improves conceptualization of the search problem

9
High-Altitude Visual Search LRC
10
Low-Altitude Visual Search LRC