|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
Earth radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). This length is also used as a unit of distance, especially in astronomy and geology, where it is usually denoted by R⊕.
The rod or perch or pole is a surveyors tool and unit of length equal to 5 1⁄2 yards, 16 1⁄2 feet, 1⁄320 of a statute mile or one-fourth of a surveyor's chain and 5.0292 meters.