1. Daryl - October 3, 2009

   I have had a read of both the document and also the presentation, but obviously without seeing it “presented” am at a distinct disadvantage.

   What method are teams being taught to define Searcher Spacing?

   Is it still the ‘Rain dance’ and is it still calculated by visualising an object of a similar size and colour at the limit of your vision?

   If the searcher spacing is grater than this surely there will be ‘dead spots’ between each sweep that will not be searched.

   Route and Path Definition

   It seems that peoples definitions of R&P searches are different, for example I was taught (and am aware is still being taught) that a R&P is the the route, path or track plus 10m either side, not 5…

   Speed V Vegetation.

   Whilst I understand the need for speed (I’m sure there is a quote in there, possibly Top Gun….) I am a little confused how speed can be increased on a R&P search when vegetation on either side of the track is dense enough to cause the searcher to be aware of trip hazards etc unless they do not leave the path.

   Human Vs Canine

   Massive subject and I’m not going to get into it, not only that I can be easily baffled by maths….

   However in your examples a speed of 2km/h is used. Is this the ‘optimal’ suggested speed of a foot searcher? The LSDogs R&P assessment dictates that the minimum speed that should be around 4km/h, although we give a little extra allowance for navigation and decision making.

2. Robert Bradley - October 3, 2009

   “If the searcher spacing is greater than this surely there will be ‘dead spots’ between each sweep that will not be searched.”

   We now have a much better understanding in lowland search of how a person “sees” when searching. Traditional thinking, and the technique of critical seperation, seem to be based upon the premise that searchers see in a solid block out to a certain point, then nothing more outside this. In reality, searchers may miss an object quite close to them yet see an object further than the average maximum detection range (AMDR – a technical term describing a figure roughly equal to the figure found by Northumbrian Raindance.) These gaps in vision can be described mathematically using search theory, whereby we can arrive at approximate probabilities of detection and probabilities of success.

   I can only obviously speak of UKLSI and ALSAR Units taught by them, but the Northumbrian Raindance is still taught as a field technique for estimating how far away you can detect an object and for determining searching spacing but team leaders are given taught to spread out more when possible.

   “It seems that peoples definitions of R&P searches are different, for example I was taught (and am aware is still being taught) that a R&P is the the route, path or track plus 10m either side, not 5…”

   ALSAR has always taught R&Ps to be 5 metres – the 10 metre figure came about when LSDogs were devising their assessment criteria and despite it only being a test it seems to have been taken as the distance a R&P should be done to. Of course, once someone has been taught this figure – they teach it to others and so it perpetuates.

   “I am a little confused how speed can be increased on a R&P search when vegetation on either side of the track is dense enough to cause the searcher to be aware of trip hazards etc unless they do not leave the path.”

   Team Leaders are now being given a lot greater flexibility – if the undergrowth is dense then it is likely that searchers will not go in – unless there is sign of possible disturbance / entry. If there is a dense patch, with open ground to the outside, the Team Leader may choose to send a searcher to the other side – Team Leaders are now being taught to micromanage their team less (you really don’t have to actually be able to see your searchers ALL the time to safely manage them!) However if a R&P has open ground to both sides the searchers may be placed 50 metres or more out.

   “However in your examples a speed of 2km/h is used. Is this the ‘optimal’ suggested speed of a foot searcher? The LSDogs R&P assessment dictates that the minimum speed that should be around 4km/h…”

   The US Coastguard sweep width experiments results reported that the average speed of searchers was “remarkable consistent” at 1.75km/h. It goes on to state that “searcher speed when kept between 1 – 3km/h did not affect sweep width”. It goes on to state “it is assumed at much slower or faster speeds a difference would occur.”

   Obviously there is a difference between dog and foot search – the primary search sensor is the dog’s nose and so the speed of the handler will not affect it’s detection ability. It does, however, affect the detection ability of the handler themselves (although how much searching they can do whilst being aware of the dog is debateable – I believe most “misses” are generally attributed to handler error) and also the support.

   Of course, there is a lack of data in the area of lowland dog search for any definitive answer to be given as to whether they should be moving faster or slower.

3. Daryl - October 4, 2009

   Hmm, ok….

   I understand that peoples depth perception may vary depending on a number of variables, but surely if an item is in the gap that would be between the maximum (or average) distance that a searcher sees, the item will not be detected?

   So from using the Raindance, it is basically being taught that purposeful wandering should be the norm with a “Common Sense” method of searching – i.e. if you cant get in, neither can the MISPER?

   When LSDogs setup their assessment they used (or wanted to use) the same distance either side of a track as ALSAR so as to use “common” terminology. I know that the data was taken from an ALSAR units BST course (as it was known back then). Unfortunately now that that this terminology has been agreed in a joint national standard with NSARDA, I don’t think it is likely that LSDogs will be reducing it to 5 meters.

   To be honest Dog Handlers (well mine anyway) are taught clue conciousness, they are also taught all of the core syllabus determined by ALSAR (as this is an LSDogs requirement so that our handlers and support can take part in a foot search where appropriate) however when searching with a dog clues are not normally looked for unless they carry human scent (i.e. clothing etc.) as the priority is to save life, and therefore to move as quickly as possible to locate the MISPER.

   So the crux of the new training is, to use the methods always taught to determine spacing, but to promote a common sense method of searching where searchers do not need to search “everywhere” but to search where is most probable?

4. Robert Bradley - October 5, 2009

   “…but surely if an item is in the gap that would be between the maximum (or average) distance that a searcher sees, the item will not be detected?”

   It is here where the problem actually lies. The Raindance gives an average figure. Not only that but searchers will, if they do one at all (but that is another argument for another day), place the object not in the typical vegetation or envirnoment, but in the thickest bit of it.

   Searcher spacing is then calculated on the thickest bit, or at best an average figure. Searchers will almost always be able to see outside this area. They will not pick up everything outside the area – in fact they might only pick up 5% of objects out that far – but there will be some detection out there. Likewise they will miss 5% of objects within 5 metres.

   It is impossible then to think about filling in gaps in search coverage. You need to rely upon the fact that the maths can give the search management team a good idea of the integrity or effectiveness of the search.

   The point of the presentation is, though, that many ALSAR Units in a bid to fill in all those gaps, now search too close together, find every little clue, and therefore aren’t actually doing the best for the misper.

   If I was to say what the crux of the new training is, although I hadn’t actually thought about it much, is that searchers cannot subjectively predict their search effectiveness. So asking team leaders to do so is a waste of everyone’s time. Searcher spacing in the past has been a reflection of the team leader trying to impose some mythical “best” search effectiveness on his search. In reality s/he cannot tell and just needs to get out there and search. It is up to search managers to weigh up how effective s/he has been.

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