A survey Chain from Edmund Gunter's system having 100 metal links and being 66 feet, or 4 rods, in length. Used in land surveying. One chain (Gunter's Surveyor's)is 4 rods, 22 yards, or 66 feet. 1 ch (Gunter's Surveyor's) = 20.1168 m (SI base unit).
1 Yard (International):
Imperial/US length of 3 feet or 36 inches. In 1959 defined in terms of metric units as exactly 0.9144 meters. 1 international yard is exactly 0.9144 meters (SI base unit of length). 1 yd = 0.9144 m.