International Ellipsoid of Reference

The International Ellipsoid of Reference is a mathematical model used in cartography to represent the Earth's size and shape. It's a type of ellipsoid, specifically an oblate spheroid, which is a flattened sphere. This shape approximates the geoid, a more complex surface that represents mean sea level. The ellipsoid is chosen for its mathematical simplicity, making calculations for maps and geodetic surveys more manageable. It is defined by its semimajor (equatorial) and semiminor (polar) axes, which differ by about 21 kilometers. This reference surface is crucial for creating accurate maps and understanding Earth's geometry.123