Monday, 4 June 2012

SAR Starting Point Two

When does Search and Rescue (SAR) start looking for for you? Where do they start looking? How long do they look for? These are three important questions and by understanding the answers, you can greatly increase your chances of survival. SAR Starting Point One answered the first of these, this article takes on the second.

Most people think that SAR teams start looking for you where you were last known to be (last know position), but although this is useful, it's not the case. Quite often, the last known position is vague at best and almost always, you're not still there. The truth of the matter is that SAR start looking where they think you are (estimated position) though this is generally an area and though calculated using a simple algorithm, can involve complex maths, psychology and analysis of the environment; all this is taken over time and re-evaluated in the context of any new evidence. By understanding this method in conjunction with good signalling, you can give yourself the best possible chance of being located, should you find yourself in a situation where you want someone to find you, which let's face it, is rather the goal in a survival situation.

First SAR starts with where you were, then where you were going. They consider route, speed, weather, motivation and "other" and now add time as a factor. A simple example might be a plane which checks in a 1200 with position, course and speed. Having not checked in at 1300, we have a rather good idea about the possible places that plane could be based on a maximum of an hour of travel from a known position at a known speed in a known direction. Of course there are some interesting weather consideration and a few unlikely affectors, but to give the greatest chance of rescue, resources are initially deployed into an area where the plane is almost certain to be, with a probability of about 80%. 

Let's next take this partial Mayday call:
"Mayday, mayday, mayday, this is fishing vessel Polly, Polly, Polly, mayday, BD123 Polly, two miles north of Hartland Point, engine and power fai..." and the radio goes dead.
You may have wondered why the mayday call is in that order; there is a very good reason. From a SAR perspective, the more we know, the better. It would be very nice to know that there were ten people on board, all wearing life jackets and that the there were no medical problems or fires, but if the radio had cut out whilst the casualty (remember, it's just a term) was relaying that, they would have missed the position, which is frankly far more important. That's why it's one of the first things in the call. With only the information above, the coastguard sets to work. An approximate starting position is given. Chances are someone would have mentioned if it was sinking, so it sounds like it's just drifting. The license number will give the coastguard an accurate size and aspect of vessel and with wind and tidal information, a trajectory. If it's going to take 30 minutes to get on scene, then they can have a good idea where Polly will have drifted to. By applying an error factor to all the input variables, a resultant search area can be determined.

Walkers and mountain bikers represent a much more interesting problem when determining a search area, but the same basic principal or position, direction and speed are applied. On Dartmoor, for instance, even the footpaths represent a maze of possibilities for changes in route, let alone areas where going "off piste" is considered the norm. The two principal reasons why recreational walkers don't come back on time is because they are lost, or because there is a medical problem, even if that's simply fatigue.  My plan from the first article gives route and approximate timings for the day, and so if I didn't make it back to the camp site, or more likely, if I didn't check in (which is something I do), then sufficient information would have been given to give a minimal search area over Snowdon. Conversely, someone with no route plan could be anywhere in North Wales (well, not really if their car is found), which is a much wider area to search. Let us suppose we check in at the top. That's a nice last known position and time and with a route set, so I've realistically got to be in the second half of the plan. A quick survey of a few walkers coming off the hill on intersecting routes may give extra info about where I'm not, which is arguably just as important in reducing the search are down.

I recently performed a safety check on a coast path route for a sponsored walk. This was not only to determine the quality of the track, but to gauge progress, chances of getting lost and dangers en route. With this, I gave recommendations for check in points, medical stations and watering areas. This was not only to reduce the chances of a situation occurring, but to give the ability for a swift response over a small search area, which is important when the poor chaps from St John's have to carry all the medical gear up and down the steep paths.

Whilst out with Exmoor Search and Rescue, I was enthralled by the level of detail to which they applied age, gender and history as well as the basics when setting up search areas for despondent and mentally ill "wanderers". With extensive training and statistical backup, they are able to make what appear to be staggering assumptions, greatly reducing the search area giving excellent results.

So what have we learnt here? Essentially, any SAR agency has limited resources and by application of basic principals, experience and some maths, they will determine a search area where they can apply those resources giving the best probability of detection possible. With position, direction and speed as the main contributing variables, the greater the accuracy of these, the less margin for error has to be applied and importantly. the smaller the time window over which the calculation has to be applied, the smaller search the area will be and the more likely you are to be found quickly.

Here are some thoughts on route plans. Have a good hard think about your route and how you imagine SAR teams might try to find you. That will give you some idea of how accurate your route plan should be in conjunction with how often you should be checking in. The more accurate and detailed your route plan, the more likely the SAR agency will assume that you are following it and so tighten the search area around it. The more you deviate from they think you are going, even if this is to try to take a short cut, the more likely it is that you will find yourself outside of the initial search area and so the more accurate your plan, the more important it is to log ad hoc changes. An alternative (or better, a combination) is to log short cuts and "bug out" routes as part of the original plan. If, however, your route plan is woolly or subject to change then state is as such, but then check in more often as this will mitigate the problems caused by an inaccurate estimated position.

Balance route planning with checking in. Always know even roughly where you are. Think hard about the effect of changing route. Know your capabilities and know the capabilities of the relevant SAR agencies and you'll greatly increase your chances of being located and hence increase your chances of survival.

Once again, if you think that all these routes and check ins lack spontaneity, then be aware that the spare paddle bearer will necessarily take longer to find you up the proverbial creak.

In the next article on this subject, I will discuss what happens if SAR don't find you in that initial search area, how long they keep looking, what happens if they find clues, how you can help them if you have no ability to check in, what to do if you do get lost and how best to manage route changes.

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