Use of the visual range of detection to estimate effective sweep width for land search and rescue based on 10 detection experiments in North America.
OBJECTIVE
Standard-of-practice search management requires that the probability of detection (POD) be determined for each search resource after a task. To calculate the POD, a detection index (W) is obtained by field experiments. Because of the complexities of the land environment, search planners need a way to estimate the value of W without conducting formal experiments. We demonstrate a robust empirical correlation between detection range (Rd) and W, and argue that Rd may reliably be used as a quick field estimate for W.


METHODS
We obtained the average maximum detection range (AMDR), Rd, and W values from 10 detection experiments conducted throughout North America. We measured the correlation between Rd and W, and tested whether the apparent relationship between W and Rd was statistically significant.


RESULTS
On average we found W ≈ 1.645 × Rd with a strong correlation (R(2) = .827). The high-visibility class had W ≈ 1.773 × Rd (also R(2) = .867), the medium-visibility class had W ≈ 1.556 × Rd (R(2) = .560), and the low-visibility had a correction factor of 1.135 (R(2) = .319) for Rd to W. Using analysis of variance and post hoc testing, only the high- and low-visibility classes were significantly different from each other (P < .01). We also found a high correlation between the AMDR and Rd (R(2) = .9974).


CONCLUSIONS
Although additional experiments are required for the medium- and low-visibility search objects and in the dry-domain ecoregion, we suggest search planners use the following correction factors to convert field-measured Rd to an estimate of the effective sweep width (W): high-visibility W = 1.8 × Rd; medium-visibility W = 1.6 × Rd; and low-visibility W = 1.1 × Rd.
Center for Earth and Environmental Science Research, Kingston University London, Kingston-upon-Thames, UK. Electronic address: r.koester@kingston.ac.uk.
Robert J
RJ
Koester
Allegheny Mountain Rescue Group, Pittsburgh, PA.
Kenneth B
KB
Chiacchia
C4I Center, George Mason University, Fairfax, VA.
Charles R
CR
Twardy
Akron General Health System, Medical Education Research, Akron, OH.
Donald C
DC
Cooper
Office of Search and Rescue, United States Coast Guard, Washington, DC.
John R
JR
Frost
Research and Development Center, United State Coast Guard, Groton, CT.
R Quincy
RQ
Robe
D006801:Humans; D008962:Models, Theoretical; D009656:North America; D018635:Rescue Work
SAR; effective sweep width; missing persons; probability of detection; range of detection; search and rescue; search theory