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Distance still to run when you hand over the watch

Why it matters The figure you hand over is what the next officer plans the watch and the pilot's arrival on; a wrong one is passed down the whole night.

The watch handover: speed × the full watch comes off the distance you were handed; an earlier stoppage does notA track to scale from the start of the watch to the pilot station, 263.6 nm. The watch runs 13.4 kn × 4 h = 53.6 nm, so 263.6 − 53.6 = 210.0 nm is handed over. The 0.5 h stoppage of the previous watch lies before the start and is already inside the 263.6 nm; taking it out again gives 216.7 nm, the wrong figure.DISTANCE TO RUN · ONE TRACK, TO SCALEstart of your watch263.6 nmto the pilot stationpilot stationprevious watchstopped 0.5 halready in the figure1234hyour watch13.4 kn × 4 h = 53.6 nmhand over210.0 nm to run216.7 nm: a 3.5 h watch,stoppage taken out again

Words on this page

Watch
the officer's turn of duty on the bridge, usually four hours.
Handover
the moment one officer passes the watch to the next, with the position and the distance to run.
Distance to run
the miles still to go to the next point, here the pilot station.
Pilot station
the place at sea where the pilot comes aboard to take the ship in.
Speed being made
the speed the ship is really covering ground at now.
Stoppage
a spell with the engines stopped, when no distance is run.
nm and kn
a nautical mile (nm) is 1852 metres; one knot (kn) is one nautical mile an hour.

An everyday picture

Three friends share a long drive. The first hands over with 300 km left on the sign. She had stopped for coffee for half an hour; the 300 km already allows for that.

You drive the next two hours at 90 km an hour. That is 180 km, so you hand over with 120 km left.

Her coffee stop is not your problem. Taking it off your two hours would say you drove less than you did.

The rule

  • Start from the distance you were handed at the start of the watch.
  • Your watch covers speed × the hours it runs. A four-hour watch at the speed being made runs four hours of miles.
  • Take that run off what you were handed. What is left is what you hand over.
  • A stoppage in the PREVIOUS watch is already inside the distance you were given. It is why that distance is what it is; do not take it off again.
  • A stoppage or a slow-down in YOUR watch is different. It comes off your own run, and you hand it over with the figure.

Formula

  • Run in the watch = speed being made × length of the watch
  • Distance to run at handover = distance at the start − run in the watch

Worked example

Distance to the pilot station at the start of the watch263.6 nm
Speed being made13.4 kn
Length of the watch4 h
Time the engines were stopped during the previous watch0.5 h
  1. Run in the watch = 13.4 × 4 = 53.6 nmSpeed times the whole watch gives the miles this watch covers; the earlier stoppage plays no part.
  2. Distance to run at handover = 263.6 − 53.6 = 210.0 nmTake those miles off the figure you were handed; this is the figure you hand on.

Answer210 nm

Common mistake

Running the watch for 4 − 0.5 = 3.5 h, the earlier stoppage taken out.

The engines stopped before the 263.6 nm was measured, so that half hour is already in it. Your watch still runs its full 4 h. The short watch gives 216.7 nm, 6.7 nm too many. The next officer then plans on a ship further out than she is.

Note for mariners If the clocks are altered in your watch, the watch runs longer or shorter; use the hours it really runs, and anything that happens in YOUR watch comes off your figure.