Chain
A chain is a unit of length traditionally used in land surveying. The most common version is the Gunter’s chain, which equals 66 feet or 22 yards, approximately 20.1168 meters.
The chain was introduced by English clergyman Edmund Gunter in the 17th century to simplify land measurement. One chain consists of 100 links, each 0.66 feet long. It became a standard unit in British and American land surveying and was instrumental in defining land areas, especially in the U.S. Public Land Survey System.
Key Conversions:
1 chain = 66 feet
1 chain = 22 yards
1 chain ≈ 20.1168 meters
10 chains = 1 furlong
80 chains = 1 mile
Though now largely replaced by metric units and modern surveying tools, the chain still appears in older land deeds, maps, and rural property descriptions.
Gigameter
A gigameter (Gm) is a unit of length in the metric system, equal to 1 billion meters (1 Gm = 10⁹ meters). Gigameters are used to measure very large distances, often within the solar system. For example, the average distance from Earth to the Sun is about 150 gigameters, or 1 astronomical unit (AU). While not commonly used in everyday life, gigameters are helpful in astronomy and space science to describe distances between planets or other celestial bodies.