reference ellipsoid

representation of the Earth

• 
  In ellipsoid

  …ellipsoid of revolution (called the reference ellipsoid) is used to represent the Earth in geodetic calculations, because such calculations are simpler than those with more complicated mathematical models. For this ellipsoid, the difference between the equatorial radius and the polar radius (the semimajor and semiminor axes, respectively) is about 21…

  Read More
• 
  In geoid

  …represent Earth is called a reference ellipsoid. This ellipsoid of revolution is the shape most often used to represent a simple geometric reference surface.

  Read More