Ordinary, geographic, or Laplace latitude, the angle between the Earth’s axis and a tangent to the ellipsoid that approximates the Earth's shape; see Figure G-1. Geodetic latitude differs from geocentric latitude ; because of the ellipticity of the Earth; (approximately) in minutes of arc. The maximum difference (at 45°) is about 21.5 km. Geodetic latitude also differs from astronomic latitude; where the mass distribution causes a vertical line not to be perpendicular to the ellipsoid. Sometimes a location is projected parallel to the Earth's axis onto a sphere whose radius is the ellipsoid’s major axis; then the angle between the axis and a radius to this point is the reduced latitude.