SaRvectorslgflnet Introduction from the Coastguard Watch this video SaR planning overview Alternatively you can use the links on the next slide to watch the three sections separately ID: 531793
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Slide1
Vectors lesson
SaRvectors.lgfl.netSlide2
Introduction from the Coastguard
Watch this video:
SaR
planning
– overview
Alternatively,
you can use the links
on the next slide to
watch the three sections separately.Slide3
Drifting from the start
There are different factors that will act to move a vessel from its drift start position
:
SaR
planning 1 - drift pattern
SaR
planning 2 - wind-driven current
SaR
planning 3 - leeway drift
Coastguards
combine these three vectors (direction and magnitude) to identify movement through the water, or ‘relative track
’.Slide4
Error factorsThere are a number of unpredictable factors that may affect a target's position after drifting.
Using the normal distribution curve, the
Coastguard
predict that 90% of targets will be within 0.3 x the distance travelled from the drift start position.
They use this to identify a search area around the datum
.Slide5
KeywordsDatum
– the
estimated location of a target after it has moved through the water.
IPE (Initial Position Error)
– the
possible error (radius) of the initial reported target position.
Relative track
– the
overall vector that the target drifts by taking into account the tidal drift, wind driven current and leeway drift
.Slide6
Scenario
A boat has run out of fuel, and has made a distress call with its estimated location 1 hour ago.
As a
Coastguard
, you will need to perform calculations to find a suitable search area.
Tidal drift: 4NM/hr
160°
Wind driven current: 6NM/hr
200°
IPE (Initial Position Error): 2NM Slide7
Scenario
First, we need to mark on the tidal drift.
Tidal drift: 4NM/hr
160°Slide8
Scenario
Then, we need to mark on the wind driven current.
Wind driven current: 6NM/hr
200°Slide9
Scenario
You need to then mark on the datum, and the resultant vector, or ‘relative track’.
This will tell you the distance from the initial drift position which is required to find the search area.Slide10
Scenario
You need to then mark on the search area.
You need to include the IPE radius of 2NM.
You need to add the error factor calculation which is 0.3 x the distance from the initial drift position = 0.3x9.5 = 2.85NM.
This means that the search radius = 2 + 2.85 = 4.85NMSlide11
Extension – divergence
The leeway drift can affect different vessels in different ways. The
Coastguard
can calculate this divergence and will create 3
datums
:
‘Downwind’ - the standard datum
D
min
- the datum found by identifying the leeway drift
30°
towards the drift start position
D
max
- the datum found by identifying the leeway drift
30°
away from the drift start
positionSlide12
Example scenarioWatch this video:
SaR
scenario
1