Titanic's Dead Reckoning Plot


Doug Criner

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American Practical Navigator, by Bowditch and Modern Seamanship, by Knight advise that a ship's dead reckoning plot should be updated every hour, on the hour. I wonder what White Star Line's rules specified? After the accident, both the Capt. and Mr. Boxhall endeavored to determine the ship's position, for an emergency message, by extending a DR plot from the last celestial fix. Both officers came up with mistaken positions. So, it seems that an updated DR plot was not being maintained. The mistaken position probably did not delay rescue efforts, but still.... The need for two officers to work on a DR position may have distracted them from attending to some other important activities. Was the failure to maintain a DR plot simply the customary practice at the time or does it possibly speak to some deviation from established practice?
 
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Mar 22, 2003
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I wonder what White Star Line's rules specified?
Doug,
The WSL rules that were in effect at the time required that the ship's position at noon was to be determined and posted ASAP after noon sights were taken of the sun, the ship's noontime position put on the chart, and a new course laid off at that time. Also upon sighting of land when possible. As far as DR positions, the ship's logbook had places for the ship's 8am DR, 8pm DR, and noontime DR to be entered (as well as the noontime fix). Other than that, I am not aware of any other "rule" that had to be followed. But there were other navigational practices that were followed like taking morning and evening star sights when possible (which used the ship's DR position at sight time to begin with) as well as morning and evening sights of the sun to determine longitude when the sun was well to the east or west, also using a DR to begin with. The morning sight would also be used to make any corrections to the ship's clocks for vessels carrying apparent time.
 

Doug Criner

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Dec 2, 2009
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As far as DR positions, the ship's logbook had places for the ship's 8am DR, 8pm DR, and noontime DR to be entered (as well as the noontime fix).
If there had been an 8pm DR, advancing it a few hours for the emergency messages should have been very simple.
 

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