__NOTOC__ The International Latitude Service was created by the

International Geodetic Association ) , merged = , successor = , formation = , founder = , founding_location = , extinction = , merger = , type = scholarly society , tax_id ...

in 1899 to study variations in

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...

caused by

polar motion Polar motion of the Earth is the motion of the Earth's rotational axis relative to its crust. This is measured with respect to a reference frame in which the solid Earth is fixed (a so-called ''Earth-centered, Earth-fixed'' or ECEF reference ...

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In oth ...

, or "wobble" of the Earth's axis. The original ''International Latitude Observatories'' were a system of six

observatories An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. His ...

located near the

parallel Parallel is a geometric term of location which may refer to: Computing * Parallel algorithm * Parallel computing * Parallel metaheuristic * Parallel (software), a UNIX utility for running programs in parallel * Parallel Sysplex, a cluster of ...

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 Gaithersburg ( ), officially the City of Gaithersburg, is a city in Montgomery County, Maryland, United States. At the time of the 2020 U.S. Census, Gaithersburg had a population of 69,657, making it the ninth-largest location in the state. Gai ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

Cincinnati, Ohio Cincinnati ( ) is a city in the U.S. state of Ohio and the county seat of Hamilton County. Settled in 1788, the city is located at the northern side of the confluence of the Licking and Ohio rivers, the latter of which marks the state line wi ...

, United States *

Ukiah, California Ukiah ( ; Pomo: ''Yokaya'', meaning "deep valley") is the county seat and largest city of Mendocino County, California, with a population of 16,607 at the 2020 census. With its accessible location along the U.S. Route 101 corridor, Ukiah serves ...

, United StatesHogle, Gene ''NAC Green Book of Pacific Coast Touring'' (1931) National Automobile Club p.43 *

Mizusawa, Iwate was a city located in Iwate Prefecture, Japan. It is currently part of the city of Ōshū. Mizusawa is home to one of the six International Latitude Observatories. The observatories were close to the parallel of 39 degrees 8 minutes north lati ...

, Japan * Charjui, Turkmenistan *

Carloforte Carloforte (''U Pàize'' in Ligurian, literally: ''the village, the town'') is a fishing and resort town located on Isola di San Pietro (Saint Peter's Island), approximately off the southwestern coast of Sardinia, in the Province of South Sar ...

, 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 World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. 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 Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...

. The final six observatories were located, in order of Longitude (E to W), in: *Gaithersburg, Maryland, USA,

Gaithersburg Latitude Observatory The Gaithersburg Latitude Observatory is a historic astronomical observatory on DeSellum Avenue in Gaithersburg, Maryland. It was established in 1899 as part of a system of six International Latitude Observatories to precisely measure the wo ...

: *Cincinnati, Ohio, USA: *Ukiah, California, USA: *Mizusawa, Japan, National Institutes of Natural Sciences National Astronomical Observatory of Japan, Mizusawa VERA Observatory: *Kitab, in

Uzbekistan Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked co ...

: *Carloforte, Italy: The ILS was renamed International Polar Motion Service (IPMS) in 1962. It was replaced when the

International Earth Rotation Service The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Pa ...

(IERS) was established in 1987.

References

External links

National Park Service
- ''The history of the Gaithersburg Observatory in Maryland, and the overall project''. {{Authority control 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

See also

References

Further reading

External links