#great_circle__greatcircle  a circular line on the surface of a sphere formed by intersecting it with a plane passing through the center
  supertype:  #line.location  a spatial location defined by a real or imaginary unidimensional extent
  subtype:  #celestial_equator__celestialequator__equinoctial_circle__equinoctialcircle__equinoctial_line__equinoctialline__equinoctial  the great circle on the celestial sphere midway between the celestial poles
     subtype:  #right_ascension  an arc of the celestial equator eastward from the vernal equinox
  subtype:  #ecliptic  the great circle representing the apparent annual path of the sun; the plane of the Earth's orbit around the sun; makes an angle of about 23 degrees with the equator; "all of the planets rotate the sun in approximately the same ecliptic"
  subtype:  #equator  an imaginary line around the Earth forming the great circle that is equidistant from the north and south poles; "the equator is the boundary between the northern and southern hemispheres"
  subtype:  #celestial_horizon__celestialhorizon__horizon  the great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the Earth
  subtype:  #hour_circle  a great circle on the celestial sphere that passes through both celestial poles
  subtype:  #meridian__longitude__line_of_longitude  an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator; "all points on the same meridian have the same longitude"
     subtype:  #observer's_meridian  a meridian that passes through the observer's zenith
     subtype:  #prime_meridian__primemeridian  meridian at zero degree longitude from which east and west are reckoned (usually the Greenwich (England) longitude)
     subtype:  #magnetic_meridian  an imaginary line passing through both magnetic poles of the Earth
     subtype:  #date_line__dateline__International_Date_Line  an imaginary line on the surface of the earth following (approximately) the 180th meridian
  subtype:  #vertical_circle  a great circle on the celestial sphere passing through the zenith and perpendicular to the horizon

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