TECHNIQUES FOR VISUAL FIXING
RYA CHART 3 and TRAINING ALMANAC Use variation 6° W and the deviation table where required.
1.
At 0100, following a long open water passage an EP with a log reading of 100.5 is plotted at 45°37´.95N 006°21´.80W. You estimate the area of uncertainty around the EP has a radius of 5.0M.
a) List the factors that you should take into account when estimating a circle of uncertainty. b) Plot the EP and draw the circle of uncertainty. c) The echo sounder shows a depth reduced to soundings of 30m. How does this depth alter the area of uncertainty?
d) A bearing of 105°(M) is plotted to Saint Stephen’s Point light. Plot the bearing and update the EP. Comment on the reliability of the fix, suggest how it could be improved.
2.
A fix is plotted during the daytime for a vessel off Gordon’s Bay. The summit on Robens Island in transit with Outer Robens lighthouse. Bearing to Outer Stack lighthouse 152°(M).
a) Plot the fix b) Choose another charted object and plot a third position line to enhance the fix c) How did you decide what to use for the third position line?
3.
A vessel is approaching Sweetwater Bay at night. To visually monitor progress, bearings have been pre-plotted from Cape Saint Vincent lighthouse out to the 30m contour line off the coast.
a) Starting at 085° and increasing by 10° increments plot the bearings up to 145°. b) Choose another charted feature from which bearings can be drawn in order to create a visual web of bearings. Plot a series of bearings from your chosen charted feature to enable progress towards the destination to be monitored while underway.
c) Within the web there is an area where the bearings may become unreliable. Why is this? d) Rather than providing precision a pre-plotted web is more useful for providing a quick reference to a sector. For which of the following might a quick sector reference be useful? i) Navigating a fast powerboat ii) Navigating a yacht beating to windward iii) Navigating a displacement motor vessel iv) Navigating a yacht sailing with a free wind
4.
A running fix is plotted from a vessel off Dymond Reef, to Token Rocks lighthouse. 1st bearing 110°(M)
2nd bearing 050°(M)
Half hour run between bearings: 155°(C) 4.0M Tidal direction and rate 184°(T) 1.8kts
a) Plot the fix b) Is it necessary for the water track to be plotted from a specific point?
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