Celestial navigation, also known as astronavigation, is the ancient and continuing modern practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space (or on the surface of the earth) without having to rely solely on estimated positional calculations, commonly known as "dead reckoning", made in the absence of GNSS (GPS, Glonass, Galileo, etc...) or other similar modern electronic or digital positioning means.