Earth radius

The Earth's radius (represented as R🜨 or ) is the distance from the center of Earth to a point on or near its surface.  

 Length 
Earth is shaped like a slightly flattened ball (an oblate spheroid). Because it is not perfectly round, Earth's radius varies.  
At the Equator, Earth's radius (called the equatorial radius) measures about 6,378 km (3,963 miles). At the North and South Poles, the planet's radius (called the polar radius) is slightly shorter: around 6,357 km (3,950 miles). The global average has been estimated at . 

 Definitions 
Earth's radius can also be defined and measured using the radius of curvature. This calculation considers land and sea topography. As a result, it can produce a different result than measurement of the equatorial or polar radiuses.

"Earth radius" is sometimes used as a unit of measurement in astronomy and geophysics.  The International Astronomical Union recommends that "Earth radius" should equal the planet's equatorial radius.

 References 

Category:Earth
Category:Geodesy
Category:Units of length