Navigational Instruments Flashcards
What is dead reckoning?
A navigator measured the heading and speed of the ship, the speed of the currents and the downwind drift of the ship, and the time spent on each heading. The navigator would us e the information to compute and course the ship made. Good dead reckoning relies on good instruments.
What is an astrolabe?
A large brass ring fitted with a sighting rule. The user held the instrument by a loop on the top and turned the sighting rule to sight the star along its length, and read the scale engraved on the ring. The astrolabe was used to determine latitude by measuring the angle between the horizon and Polaris.
What is a Quadrant?
A navigational instrument shaped like a quarter-circle made of wood or brass. The user measured the altitude of the North Star by estimating through a peephole and measuring the angle of Polaris to the instrument. This matters because people needed to measure altitude.
What is a magnetic compass?
A navigational instrument that always points to somewhere around direct North no matter where you were. The compass was used mainly in the past to measure wind direction, but was then used to find headings, which helped with dead reckoning, which allowed the location and time of where the ship was.
What is a traverse board?
A traverse board is piece of circular wood on which a compass rose was painted on it. There were eight small holes spaced evenly along the edge of each point, and eight pegs that were attached with string to the center of the board. Evert half-hour one of the pegs would be stuck into the next hole, so the compass rose would point closest to the heading the ship had maintained for that half hour. A traverse board was used to help find measurement for dead reckoning.
