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

Calculating an ETA

• Measure the distance along the course line to the destination in nautical miles

Calculating an ETA

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

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.

6 Minute Finger Method

6 Minute Finger Method

• Alternatively put two fingers over the 3 nautical miles on the latitude scale, and then run them down the course line counting off 6 minutes as you go.

• This will give you somewhere around 24 minutes plus for a time travelled.