Among the earliest length measures was the foot, which varied from place to place For example, three different Greek standards are known: the Doric foot, the Attic foot and the Samian foot. There were two common sizes for a "foot" - the foot of 246 to 252 mm based on a man's bare foot - the foot of 330 to 335 mm based on two hand measurements. The first calibrated foot ruler, a measurement tool, was invented in 1675 by an unknown inventor.
Measurement Tools - Specific Instruments
- Altimeter An instrument which measures vertical distance with respect to a reference level. Louis Paul Cailletet was the French physicist who invented the altimeter.
- Carpenter Square
- Clocks The invention of the quartz watch, mechanical clocks, timekeeping devices, and time measurement.
- Protractor An instrument used to construct and measure plane angles. The simple protractor looks like a semicircular disk marked with degrees, from 0º to 180º. The simple protractor is an ancient device. The first complex protractor was created for plotting the position of a boat on navigational charts. Called a three-arm protractor or station pointer, it was invented in 1801, by Joseph Huddart, a U.S. naval captain. The center arm is fixed, while the outer two are rotatable, capable of being set at any angle relative to the center one.
- Sextant In 1731, Thomas Godfrey and John Hadley independently invented the reflecting quadrant, a precursor to the sextant. John Campbell invented the sextant in 1757. The octant could only measure latitude, and not longitude. Royal Naval Captain John Campbell's sextant could measure both longitude and latitude.