A galactic quadrant, or quadrant of the galaxy, refers to one of four circular sectors in the division of the Milky Way galaxy. In actual astronomical practice, the delineation of the galactic quadrants is based upon the galactic coordinate system, which places the Sun as the pole of the mapping system. The Sun is used instead of the galactic center for practical reasons since all astronomical observations (by humans) to date have been based on Earth or within the solar system. [wikipedia]