Great Trigonometric Survey
Encyclopedia
The Great Trigonometric Survey was a project of the Survey of India
Survey of India
The Survey of India is India's central engineering agency in charge of mapping and surveying. Set up in 1767 to help consolidate the territories of the British East India Company, it is one of the oldest Engineering Departments of the Government of India...

 throughout most of the 19th century. It was piloted in its initial stages by William Lambton
William Lambton
Lieutenant-Colonel William Lambton, FRS was a British soldier, surveyor, and geographer.Lambton was the Superintendent of the Trigonometrical Survey of India, which he began in 1802. He died and is buried at Hinganghat in Wardha district of Maharashtra...

, and later by George Everest
George Everest
Colonel Sir George Everest was a Welsh surveyor, geographer and Surveyor-General of India from 1830 to 1843.Sir George was largely responsible for completing the section of the Great Trigonometric Survey of India along the meridian arc from the south of India extending north to Nepal, a distance...

. Among the many accomplishments of the Survey were the demarcation of the British
United Kingdom of Great Britain and Ireland
The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom during the period when what is now the Republic of Ireland formed a part of it....

 territories in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 and the measurement of the height of the Himalayan giants: Everest
Mount Everest
Mount Everest is the world's highest mountain, with a peak at above sea level. It is located in the Mahalangur section of the Himalayas. The international boundary runs across the precise summit point...

, K2
K2
K2 is the second-highest mountain on Earth, after Mount Everest...

, and Kanchenjunga. The Survey had an enormous scientific impact as well, being responsible for one of the first accurate measurements of a section of an arc of longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

, and for measurements of the geodesic anomaly
Vertical deflection
The vertical deflection at a point on the earth is a measure of how far the direction of the local gravity field has been shifted by local anomalies such as nearby mountains....

.

History

The Great Trigonometrical Survey of India started on 10 April 1802 with the measurement of a baseline near Madras
Chennai
Chennai , formerly known as Madras or Madarasapatinam , is the capital city of the Indian state of Tamil Nadu, located on the Coromandel Coast off the Bay of Bengal. Chennai is the fourth most populous metropolitan area and the sixth most populous city in India...

. Major Lambton selected the flat plains with St. Thomas Mount
St. Thomas Mount
St. Thomas Mount, or Parangimalai is a small hillock located in Chennai, Tamil Nadu, India. Located near the neighbourhood of Guindy and very close to Chennai International Airport, St. Thomas Mount is associated with St. Thomas, the apostle of Christ, who is believed to have been martyred here...

 at the north end and Perumbauk hill at the southern end. The baseline was 7.5 miles (12.1 km) long. Lieutenant Kater was despatched to find high vantage points on the hills of the west so that the coastal points of Tellicherry and Cannanore
Kannur
Kannur , also known as Cannanore, is a city in Kannur district in the Indian state of Kerala. It is the administrative headquarters of the District of Kannur and 518km north of state capital Trivandrum. During British rule in India, Kannur was known by its old name Cannanore, which is still in...

 could be connected. The high hills chosen were Mount Delly
Ezhimala Hill
Ezhimala , a hill reaching a height of 286 metres, is located in Kannur District of Kerala, South India. As the former capital of the ancient Mushika Kingdom, it is considered to be an important historical site. It is a conspicuous, isolated cluster of hills, forming a promontory 38 km north...

 and Tadiandamol
Tadiandamol
Tadiandamol is the highest mountain of Kodagu district, Karnataka, India. It is located on the Western Ghats range, and reaches an elevation of 1,748 m. It is a place of interest for trekkers and naturalists. The mountain has patches of shola forests in the valleys.The Nalaknad palace at the...

. The distance from coast to coast was 360 miles (579.4 km) and this survey line was completed in 1806. The East India Company
East India Company
The East India Company was an early English joint-stock company that was formed initially for pursuing trade with the East Indies, but that ended up trading mainly with the Indian subcontinent and China...

 thought that this project would take about 5 years but eventually it took more than 60 years, draining the profits of the Company, so much so it was brought under the Crown after 1857.

Baseline measurement

The initial baseline was measured with great accuracy, since the accuracy of the subsequent survey was critically dependant on it. Various corrections were applied, principally temperature. An especially accurate folding chain was used, laid on horizontal tables, all shaded from the sun and with a constant tension.

Corrections

To achieve the highest accuracy a number of corrections were applied to all distances calculated from simple trigonometry:
  • Curvature of the earth
  • The non spherical nature of the curvature of the earth
  • Gravitational influence of mountains on pendulums
  • Refraction
  • Height above sea level

Surveyors became landowners

Many surveyors became very rich. Prominent among them was Andrew Chamrette, his son Peter Chamrette, and his grandson Charles Chamrette, who worked for the GTS of India from 1802 to 1876. This family acquired huge tracts of land in village Kapsi district Yavatmal
Yavatmal
Yavatmal is a city and municipal council of the Yavatmal district in the Indian state of Maharashtra. The name derives from the Marathi Yavat and mal .-Demographics:yavatmal ,district in Amravati administrative division....

, Maharashtra (formerly CP Berar) amounting to more than 1800 acres (7.3 km²) and George Everest
George Everest
Colonel Sir George Everest was a Welsh surveyor, geographer and Surveyor-General of India from 1830 to 1843.Sir George was largely responsible for completing the section of the Great Trigonometric Survey of India along the meridian arc from the south of India extending north to Nepal, a distance...

 bought 600 acres (2.4 km²) of land near Dehra Doon.

Further reading

  • Matthew Edney. 1997. Mapping an Empire. Chicago: University of Chicago Press. ISBN 0-22-618488-9.
  • John Keay. 2000. The Great Arc. London: Harper Collins. ISBN 0-00-257062-9.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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