CALCULATING TIME, SPEED & DISTANCE 2011. Time / Distance / Speed Calculations.
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Transcript of CALCULATING TIME, SPEED & DISTANCE 2011. Time / Distance / Speed Calculations.
Time / Distance / Speed Calculations
• All these calculations revolve around the following formula
60D = TS
Time / Distance / Speed Calculations
• T = time in minutes• S = speed in knots• D = distance in nautical miles
60D = TS
Calculating an ETA
• Measure the distance along the course line to the destination in nautical miles
Calculating an ETA
• The distance from Ladysmith (top left hand corner) to off Norway Island is 12.9 nautical miles.
• Using 60D = T
S• 60 x 12.9 = T in minutes = 25.8 minutes
30
Calculating an ETA
• Add this time to the the departure time, e.g. 0800 LT, and your ETA off Norway Island will be around 0825 LT.
6 Minute Finger Method
• This method may be used with either dividers or fingers held a set distance apart for a rapid estimation of distance.
6 Minute Finger Method
• At 30 knots the vessel will travel 3 nautical miles every 6 minutes.
• Set dividers to 3 nautical miles on the latitude scale, and then run them down the course line counting off 6 minutes as you go.