The linear unit commonly employed by surveyors is Gunter’s chain, which is 4 rods or 66 feet.
An engineers’ Chain, used by civil engineers, is 100 feet long, and consists of 100 links.
Measures of Length
The following measures of length are also used:
| 3 barleycorns | = | 1 inch. Used by shoemakers. | |||||
| 4 inches | = | 1 hand. Used to measure the height of horses. | |||||
| 6 feet | = | 1 fathom. Used to measure depths at sea. | |||||
| 3 feet | = | 1 pace. | - | Used in pacing distances. | |||
| 5 paces | = | 1 rod. | |||||
| 8 furlongs | = | 1 mile. | |||||
| 1.15 statute miles | = | 1 geographical, or nautical mile. | |||||
| 3 geographical miles | = | 1 league. | |||||
| 60 geographical miles | - | = | 1 degree | - | of Latitude on a Meridian, or of Longitude on the Equator. | ||
| 69.16 statute miles | |||||||
The length of a degree of latitude varies. 69.16 miles is the average length, and is that adopted by the United States Coast Survey.
The standard unit of length is identical with the imperial yard of Great Britain.
The standard yard, under William IV., was declared to be fixed by dividing a pendulum which vibrates seconds in a vacuum, at the level of the sea, at 62 degrees Fahrenheit, in the latitude of London, into 391,393 equal parts, and taking 360,000 of these parts for the yard.
The following denominations also occur: The span = 9 inches; 1 common cubit (the distance from the elbow to the end of the middle finger) = 18 inches; 1 sacred cubit = 21.888 inches.