To find "the longitude of places" in order to perfect navigation
The 1675 warrant stated the task of "The King's Astronomical Observator" as "rectifieing the Tables of the motions of the Heavens, and the places of the fixed stars, so as to find out the so much desired Longitude of places for Perfecteing the Art of Navigation". The Royal Astronomy at Greenwich was built for the work. Later, in 1818, the Royal Observatory was given the task of maintaining the Royal Navy chronometers.