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A handful of simple nomographs for computing Probability of Detection using the Law of Random Search

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SAR_Nomographs

This is a collection of hacks I created using PyNomo. Pynomo is also now on github at its author's repository, https://github.com/lefakkomies/pynomo.

The purpose is to provide a simple, usable set of nomographs that search planners and debriefers can use to estimate Probability of Detection (POD) or the effort required to achieve a given POD, without having to pull out a computer and spreadsheet program to do so.

In order to generate the nomographs from the scripts (or hack on them), you must first install PyNomo and all of its dependencies according to the directions on its web site. Once PyNomo is installed properly, you can just run these scripts to produce the nomographs. The scripts produce PDFs of the nomographs for viewing in any PDF viewer or incorporation into other documents.

The repository contains PDF versions of the nomographs as generated by the python scripts, so you don't have to unless you want to hack on 'em.

The two nomographs that are intended to be used are POD_from_W_v_t_simplified.pdf and POD_from_W_L_N.pdf. The others are all just toys I created while learning PyNomo and building these two.

POD_from_W_v_t_simplified.pdf is intended for planning purposes, and instructions for using it are in "PlanningNomograph_Instructions.odt", a LibreOffice document. It can be used to estimate the searcher effort (in "searcher-hours") required to achieve a given POD, knowing either the effective sweep width or the measured average range of detection, the searcher speed and region area and desired POD. Alternatively, it can be used to determine the attainable POD using a given level of effort (in searcher-hours).

Conversion between range of detection and sweep width makes use of the approximate relations described in Use of the Visual Range of Detection to Estimate Effective Sweep Widths for Land Search and Rescue Based on 10 Detection Experiments in North America.

The second nomograph, POD_from_W_L_N.pdf, is for debriefing purposes. It allows the debriefer to compute the POD of a completed search using the measured average range of detection (or alternatively the tabulated effective sweep width), the total track length of one searcher in the team (as measured by GPS), the number of searchers on the team, and the area searched. Instructions for using it are in "DebriefNomograph_Instructions.odt" (also a LibreOffice document).

PDF versions of both instruction sheets are also present in the repository, for those who cannot read LibreOffice documents.

These nomographs were created first as a little joke I was going to present to a class on search theory at the 2015 New Mexico search and rescue conference, ESCAPE, showing how search planners of the 1940s might have computed the quantities in question. Then it occurred to me that the nomograph would actually be useful even to search planners in the 21st century. Effective use of these nomographs does require familiarity with search theory and its application. I drafted a tiny web page with some useful papers and books to read if you're interested in this subject. It's at http://pages.swcp.com/~russo/searchtheoryrefs.html.

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