The second part of this series on purposeful wandering concentrates on the aim of any search. 

You would think that this would be very straightforward - to find the missing person as quickly as possible. Yet this is often not the case.

Without meaning to pick on Cheshire Police, their spokesman on search stated that "I would expect with confidence that they have searched that area " and that the searchers should be "confident no individual was missed". These aims are actually very different from finding the misper as quickly as possible and the lack of understanding of this is one that is often associated with the tactic of straight line searching.

There are a couple of abbreviations that are often bandied around in search that I need to clarify. Probability of Detection (POD) is the likelihood of finding a search object in an area given a certain level of search resource. Probability of Success (POS) is the overall likelihood of finding the search object. 

Because of the way POD is calculated maximising it - that is the likelihood of finding a search object in one area - does not necessarily maximise the POS of the search.

What this means is that sometimes, if you are concentrating on ensuring the misper is not in an area being searched you are not maximising your chance of finding them overall. 

How do you make sure someone isn't in the search area? Pack your searchers close enough together that they can see each other and "don't need to wander".

Maximising the POS of the search, that is the chance of finding the misper quickly and alive, means spacing out searchers further and having to utilise the technique of purposeful wandering.