Traverse board

The traverse board is a tool formerly used in dead reckoning navigation to easily record the speeds and directions sailed during a watch.

As the mathematician William Bourne remarked in 1571, “I have known within these 20 years that them that were ancient masters of shippes hathe derided and mocked them that have occupied their cards and plattes and also the observation of the Altitude of the Pole saying; that they care not for their sheepskinne for he could keepe a better account upon a board.” Bourne’s ‘old salt’ is talking about a traverse board, a wooden board with a compass rose drawn on it linked by pegs and cords to a series of peg holes beneath it.

It allowed a helmsman to keep a rough check of the time sailed on each rhumb[1] of the wind.

[3] At the end of the watch, the navigator collected the information about the speeds and directions sailed during the watch into the logbook, cleared the pegs from the board, and used the information to figure the vessel's dead reckoning track.

Meanwhile, the helm of the new watch would begin recording the new sailing headings and speeds on the traverse board.