Search Planning using SearchWell

SearchWell offers the following options to aid in effective search planning.

•Change the defaults – whilst default values are useful in many ways, there are times that it is advisable to change the default to adapt to specific situations:

⮚Start position of the search pattern

⮚Bearing along which the pattern will progress

•Multiple search patterns within a search box

•Splitting a search pattern between multiple rescue vessels

Terminology

•Search Box – this is the area that has been selected to be searched.  It is important to note that normally the centre of the search box is where we think it is most likely that we will find the casualty, and the outer lines and corners are where we are least likely to find the casualty.

The likelihood of finding the casualty in the search box depends upon which box was selected – 

⮚If a Probability Search Box was selected then we know the percentage chance of finding the casualty (related to the number of random particles that are found within the box)

•Search Time – for this discussion, this is the actual time available for searching – it excludes the time for the vessel to arrive in the area and the time it will take for them to return to their base.  

Factors to consider when doing search planning

What would I consider when formulating a plan to search for a casualty – 

1.The urgency -  this depends on 

a.what the casualty is  

b.the location in which they are missing …. a RIB drifting towards a known hazard would be searched for differently from a RIB that is drifting out in the open ocean

2.The rescue vessel(s) – size and number.  If we are fortunate enough to have more than one rescue vessel involved in the search, we can search the search box in much less time and, using SearchWell, in a planned and coordinated manner

3.The time available for the search – where there is a limited time to search we need to establish the area with the highest chance of finding the casualty and then prioritise this area for searching

4.The confidence level of the LKP – this would help in deciding what search pattern to initiate early in the search.  If, for instance, we are looking for a lost diver who was not seen surfacing, we don’t know the time or the position of the LKP with any degree of accuracy.  In this case, it would be better to use a search pattern that has a wider “reach” like a parallel line or zig-zag along the calculated drift path.  On the other hand, if we are looking for a bigger casualty and are relatively confident with the LKP information, it would be meaningful to search around the calculated Datum position first eg do a Sector search at the Datum point.

5.The size of the search area.  I would create more random points for the larger search areas (normally a longer drift time) and I would look at the random points in Google Earth Pro and see what the search box areas are.  This, with the other information of time left to search and available resources, would define part of the of the whole search box encompassing all the random points to concentrate the search in.

6.The casualty type we are looking for and any known details about the casualty

a.Competence of the casualty

b.Damage to the casualty

c.In some circumstances, what would the likely reaction of the casualty be – eg a lost diver …. Are they strong swimmers who know the sea and are likely to try and self-rescue – in this case, the search pattern should cater for the possibility that this might happen

7.Likely speed of drift – given that a fast-moving object is likely to diverge less than a slow-moving one, it would be good to consider the speed of drift when deciding which search pattern to use

8.Direction of the total drift path – if it is relatively straight or if conditions changed to make the drift path a curve 

A change in conditions that affect the drift direction and speed will always complicate the search planning

9.The conditions

a.Chop/swell – a person in the water is much harder to see in choppy conditions, and this will affect the speed the rescue vessel can maintain during the search, but it might also determine the best search pattern to be used

b.Visibility – if the visibility is poor eg. thick mist, the method of searching will be very different to searching on a clear day

c.Potential for areas of disturbance – which might influence the drift path more than the prevailing conditions, making “local area knowledge” important

i.River estuaries 

ii.Mountains

iii.Presence of sea-bed relief

iv.Permanent or semi-permanent rips

d.Local hazards eg foul ground, pinnacles

10.Availability of assistance from the air

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