The International Latitude Service was created by the International Geodetic Association in 1899 to study variations in latitude caused by polar motion, precession, or "wobble" of the Earth's axis. The original International Latitude Observatories were a system of six observatories located near the parallel of 39° 08' north latitude. The alignment of all six stations along the parallel helped the observatories to perform uniform data analysis. The original six observatories were located in: Gaithersburg, Maryland, United States Cincinnati, Ohio, United States Ukiah, California, United States Mizusawa, Iwate, Japan Charjui, Turkmenistan Carloforte, Italy Twelve groups of stars were studied in the program, each group containing six pairs of stars. Each night, each station observed two of the star groups along a preset schedule and later compared the data against the measurements taken by the sister stations. Economic difficulties and war caused the closings of some of the original stations, though a newer station was created in Uzbekistan after World War I. The data collected by the observatories over the years still has use to scientists, and has been applied to studies of polar motion, the physical properties of the Earth, climatology and satellite tracking and navigation. The final six observatories were located, in order of Longitude (E to W), in: Gaithersburg, Maryland, USA, Gaithersburg Latitude Observatory: Cincinnati, Ohio, USA: Ukiah, California, USA: Mizusawa, Japan, National Institutes of Natural Sciences National Astronomical Observatory of Japan, Mizusawa VERA Observatory: Kitab, in Uzbekistan: Carloforte, Italy: The ILS was renamed International Polar Motion Service (IPMS) in 1962. It was replaced when the International Earth Rotation Service (IERS) was established in 1987. See also List of astronomical observatories References Further reading External links National Park Service - The history of the Gaithersburg Observatory in Maryland, and the overall project. Astronomical observatories Astronomical observatories in Italy Astronomical observatories in Japan Astronomical observatories in California Astronomical observatories in Uzbekistan Buildings and structures in Cincinnati Buildings and structures in Mendocino County, California Astronomical observatories in Ohio Astronomical observatories in Maryland Buildings and structures in Gaithersburg, Maryland Geodesy organizations