This is the first of a couple of articles outlining the search technique of purposeful wandering. 

I never really believed that I would have to write such an article but apparently there exists some misunderstandings and indeed distrust of the technique. Sometimes these exist within SAR teams themselves, and sometimes the SAR teams are dictated to be the local police or law enforcement.

In this first article I want to concentrate on a common misconception on how well we see during search.

The very common view is that when we search an area or strip we "see" everything up to a certain distance from us, then nothing outside this. If you believe this then statements like "if they "couldn't see the ground between them" it would not be appropriate and that areas might better be sectorised so that the searchers did not need to wander" as given by the Cheshire Police Spokesman in our article on searching in straight lines make sense.

However, the reality is totally different. We do not see like this, and certainly cannot search assuming like this.

A detailed discussion on vision and search, whilst worthwhile, is not warranted here but when we are out searching we do not see in a "block" of vision. When we look we "see" in chunks of vision, at a variety of "depths" - sometimes getting a brief overview glance, sometimes concentrating on a specific area to get greater detail. This means that we will sometimes "see" something quite far away, but miss a similar object quite close and vice versa a lot more often.

There is no way we, as individuals, can predict what and where we will see things ourselves. Training helps us do a better job, but ultimately we will always see some things and miss others.

A common way of describing this is to think of a broom sweeping up sand. It will push some of the sand, but some will get left behind - falling through the "holes" of the brush.

We can, in fact, map which bits we see and these "holes" in vision through the use of search theory mathematics and this is why the US Coastguard carried out sweep width experiments for land search. So we know that actually, going back to the broom example, we will sweep up more sand near the centre of the broom (we will see a lot more closer to the searcher) and we will leave more sand near the edges of the broom (we will miss a lot more at the edges of our vision!)

But what this does mean is that walking in straight lines, whilst it will still find search objects, is not necessarily the most effective search technique. 

More on purposeful wandering coming soon...