perche

CONT: En pratique, on compte 0,304 800 m pour le pied depuis le XIXe siècle [...] Cela donne un yard de trois pieds à 0,9144 m et une perche de 16 ½ pieds mesurant 5,0292 m. Une acre de 160 perches carrées couvre ainsi 4 046,8564 m [carrées].

CONT: The rod, perch, or pole ... is a ... and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16 1⁄2 feet, equal to exactly 1⁄320 of a mile, or 5 1⁄2 yards (a quarter of a surveyor's chain), and is exactly 5.0292 meters. The rod is useful as a unit of length because integer multiples of it can form one acre of square measure (area). The ""perfect acre"" is a rectangular area of 43,560 square feet, bounded by sides 660 feet (a furlong) long and 66 feet (a chain) wide (220 yards by 22 yards) or, equivalently, 40 rods by 4 rods. An acre is therefore 160 square rods or 10 square chains.