The traverse board is a tool formerly used in

dead reckoning In navigation, dead reckoning is the process of calculating the current position of a moving object by using a previously determined position, or fix, and incorporating estimates of speed, heading (or direction or course), and elapsed time. T ...

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navig ...

to easily record the speeds and directions sailed during a

watch A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of ...

. Even crew members who could not read or write could use the traverse board. 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 A compass rose or compass star, sometimes called a wind rose or rose of the winds, is a polar coordinates, polar diagram displaying the orientation of the cardinal directions (north, east, south, and west) and their points of the compass, inter ...

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 Rhumb may refer to: * Rhumb line, a navigational path with a constant bearing * one of the 16 or 32 points of the compass (now rare) * a nautical unit of angular measure equal to of a circle or ° (now rare) See also

* Bearing (navigation) * ...

of the wind.

Description

The traverse board is a wooden board with peg-holes and attached pegs. It is divided into two parts, upper and lower. The top part is for recording direction

sail A sail is a tensile structure, which is made from fabric or other membrane materials, that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may b ...

ed. It has a representation of the

with its 32

compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with No ...

points, just as on the face of the

ship A ship is a large watercraft, vessel that travels the world's oceans and other Waterway, navigable waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research and fishing. Ships are generally disti ...

's compass. Eight concentric rings are inscribed on the compass rose. Each ring has one peg hole at each point of the compass. Eight pegs are attached to the centre of the compass rose with strings. The bottom part is for recording speed. It has four rows of holes. Each column represents a certain speed, measured in

knot A knot is an intentional complication in Rope, cordage which may be practical or decorative, or both. Practical knots are classified by function, including List of hitch knots, hitches, List of bend knots, bends, List of loop knots, loop knots, ...

s. Three more columns to the right give fractional knots: , , and . Eight pegs are attached to this part of the board. Each half-hour during the watch, a crew member inserted a peg in the top part of the board to represent the heading

ed during that half-hour, as shown on the

. The innermost ring of peg-holes is used for the first half-hour, and each succeeding measurement was made in the next ring out, until all eight rings were used. Each hour during the

, a crew member inserted a peg in the bottom portion of the board to represent the

speed In kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. Intro ...

sailed during the hour. The speed would have been measured using a knot log. If the speed for the first hour of the watch was knots, the crew member would count over 10 holes in the first row and place one peg, then place another peg in the column marked "". In the second hour of the watch, the crew member would use the second row of pegs, and so on until all 4 rows were used. 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

track. Meanwhile, the helm of the new watch would begin recording the new sailing headings and

s on the traverse board.

External links

The Pilgrims & Plymouth Colony:1620 -- Navigation: The Traverse Board
by Duane A. Cline—line drawing of traverse board

References

{{DEFAULTSORT:Traverse Board Navigational equipment