Unit Definition (chain [Gunter, survey])
The chain is a unit of distance formerly used by surveyors. The traditional British surveyor's chain, also called Gunter's chain because it was introduced by the English mathematician Edmund Gunter (1581-1626) in 1620, is 4 rods long: that's equal to exactly 1/80 mile, 1/10 furlong, 22 yards, or 66 feet (20.1168 meters). The traditional length of a cricket pitch is 1 chain. Gunter's chain has the useful property that an acre is exactly 10 square chains. The chain was divided into 100 links. American surveyors sometimes used a longer chain of 100 feet, known as the engineer's chain or Ramsden's chain. (However, Gunter's chain is also used in the U.S.; in fact, it is an important unit in the Public Lands Survey System.) In Texas, the vara chain of 2 varas (55.556 ft) was used in surveying Spanish land grants. In the metric world, surveyors often use a chain of 20 meters (65.617 ft).

Unit Definition (rood)
The rood is an old unit of distance, used in several ways. Rood (or roede) is an old Dutch word meaning a rod or pole. So the rood is in some cases another name for a rod. But in old England and Scotland the rood was often longer than a "modern" rod of 16.5 feet; sometimes it was 20 feet, 21 feet, or even 24 feet. In Afrikaans-speaking South Africa, the rood was a standardized measure equal to 12 Cape feet, which is 12.396 English feet or 3.7783 meters.