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## Lesson 8: Dead Reckoning

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**Lesson 8: Dead Reckoning**4/2/2014**Lesson 7: Dead Reckoning**• AGENDA: • Definition of Dead Reckoning • Six Rules of Dead Reckoning • Define/Apply the 3 min & 6 min Rules • Applicable reading: Hobbs pg. 134-138.**Dead Reckoning**DR is the process of determining a ship’s approximateposition by applying, from a known position, a vector or a series of consecutive vectors representing the true courses steered and the distance run as determined by the ship’s speed and time,without considering the effects of wind and current.**Dead Reckoning**• DR is derived from DEDUCED, or DED, reckoning which was the process by which a vessel’s position was computed trigonometrically in relation to a known point of departure. • This is performed as often as required by the 6 rules of DR • Uses: • Determine present position • Project future positions relative to hazards • Measure the effects of current (winds, seas) • Alter course to account the effects of current**0846**Plot a new Course Line with Every Fix or Running Fix c-075 s-15 0937 R-Fix c-106 s-10**Plot a DR Position Every Hour on the Hour**0900 1000 1100**Plot a DR Position atEvery Course Change**29 20 c-090 C-080 C-125 24**Plot a DR Position atEvery Speed Change**21 27 15 S-10 S-15 S-5**Plot a DR Position for Every Line of Position**(LOP) c-195 s-10 Tank 0826 0826**0846**Plot a DR Position for Every Fix or Running Fix 46 37 0937 R-Fix**Speed-Time-Distance Calculations**• STD calculations can be made using a nautical slide rule, electronic calculator, set of pre-computed tables, or speed nomogram. D = S x T where: D = distance traveled S = speed in knots T = time in hours**Three Minute Rule**• In 3 minutes a vessel travels in yards a distance 100 times its speed in knots. D = S x 100 where: D = distance traveled (yds) S = speed in knots**Six Minute Rule**• In 6 minutes a vessel travels in miles a distance equal to its speed in knots divided by 10. D = S / 10 where: D = distance traveled (nm) S = speed in knots**REVIEW**• What is Dead Reckoning? • What are the 6 Rules of DR?