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Measurement of the Madras Baseline

Name: Measurement of the Madras Baseline
Start: 1802-04-10
End: 1802-05-22
Location: Near Madras

When: 10 April 1802 to 22 May 1802
Where: Near Madras
Part of: Great Trigonometrical Survey of India begins

A 7.5-mile baseline was measured near Madras from April to May 1802, establishing the foundation for the survey.

The measurement began on 10 April 1802 from St. Thomas Mount and was completed by 22 May 1802, covering 7.5 miles (12.1 km). This baseline was critical for the accuracy of the subsequent triangulation. The careful survey equipment needed for this work had arrived in 1801.

Sources

Great Trigonometrical Survey Wikipedia, revision of 2026-09-24
William Lambton Wikipedia, revision of 2026-08-21

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.