The International Latitude Service[1] 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.

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International Latitude Observatory

International latitude observatory of Ukiah, California, 1909
Alternative names	International Polar Motion Service
Location	United States
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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[2]
• 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: 39°08′12.51″N 77°11′55.85″W
• Cincinnati, Ohio, USA: 39°08′20.45″N 84°25′24″W
• Ukiah, California, USA: 39°08′14.26″N 123°12′42.54″W
• Mizusawa, Japan, National Institutes of Natural Sciences National Astronomical Observatory of Japan, Mizusawa VERA Observatory: 39°08′6″N 141°07′54″E
• Kitab, in Uzbekistan: 39°08′0″N 66°52′54″E
• Carloforte, Italy: 39°08′13.76″N 8°18′41.90″E

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

• Proverbio, E. (2000). "The Period of Organization of the International Latitude Service: 1889–1899". International Astronomical Union Colloquium. Cambridge University Press (CUP). 178: 121–138. doi:10.1017/s0252921100061261. ISSN 0252-9211.

External links

• National Park Service - The history of the Gaithersburg Observatory in Maryland, and the overall project.