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1:1 ON YOUR DATE

See here for Estimated Position process: estimated_position_process.pdf

Estimated Position worked example  RYA CHART 2 Use variation 7°W.

All times are BST

At 0405 on Saturday 10th August you are in position 170°(T) 1 mile from Berry Head Light
steering a course of 200° (M). The log reads 10.5.   At 0505 the log reads 15.0.

a) Plot the EP at 0505. Use Diamond <D>.

b) What is the speed over the ground (SOG)?

c) How close to the red can buoy near The Bull will the boat pass?

Method:
  1. Plot the initial fix and check it.
  2. True course = 200° (M) – 7° (W) Variation 193° (T)
    (Note - you also need to apply Deviation and Leeway, if they apply, to find the True course from a Compass course) 
  3. Boat travels 15.0 – 10.5 = 4.5 Miles
  4. Plot the water track 193° T from the fix to the
    Dead Reckoning (DR) position (without tide)
  5. Find the tide Set and Rate (below)
  6. Plot the tide (036° T, 0.9 kn) from the DR to the EP
  7. Draw the Ground Track from the Fix to the EP

Tide
10th August HW Plymouth 0335 BST Range = 2.2m Neap.
Tide Diamond <D> 0405 - 0505
Tide ladder:
High Water 0305
0335
0405		  
HW + 1 0405
0505		 HW +1 hour Diamond <D>Tide Set = 036°(T), Neap rate = 0.9 knots.
(a) EP - 50° 19'.3N 04° 29'.4W

(b) SOG= distance from Fix to EP = 3.7 miles in 1 hour = 3.7 knots
= speed actually travelled by boat over the ground.

(c) The ground track is 1½ cables to the west of the buoy. (0.15 M)

Posted 25th May 2011