The Gaithersburg Latitude Observatory was constructed in 1899 as one of the original four stations selected by the International Geodetic Association to carry out systematic observations measuring variations in latitude caused by the Earth's wobble on its polar axis. This wobble causes small changes in latitude at every point on Earth, though not enough to affect navigation. The International Latitude Service was founded in 1899 to measure movement at the North Pole, and the U.S. Coast and Geodetic Survey, founded in 1807, appointed Edwin Smith to site and build the Gaithersburg observatory. The service built six observatories around the world near the parallel of 39 degrees 08 minutes north, with the first four established in 1899 at Gaithersburg, Maryland; Ukiah, California; Mizusawa, Japan; and Carloforte, Sardinia, Italy, later relocated to Cagliari in 1978. The same groups of stars were measured each night according to a predetermined schedule, although observations were interrupted at times by weather, military actions, funding, and earthquakes. These measurements confirmed the irregular daily motion of the Earth's axis, and the knowledge gained remains useful for precise navigational patterns of orbiting satellites and for space travel. The International Latitude Service was renamed the International Polar Motion Service in 1962. The Gaithersburg Observatory operated until 1982, when satellites replaced human observers, and the International Polar Motion Service ended in 1988 when the International Earth Rotation Service was organized. Data collected by the International Latitude Service and satellites continue to provide important scientific information about polar motion, tidal action and fluid movements within the Earth, and weather changes, and Gaithersburg remains an active site because Global Positioning Satellite systems use Coast and Geodetic Survey markers installed on the grounds for periodic course corrections.