The Trials and Errors of Colonial Geography: The Great Trigonometrical Survey and Experiments with Triangulation

When the British came to India, what they lacked was a map that tied together all the different kingdoms and empires. Each map that existed which was patronized by individual Kings, had extreme variances. The Enlightenment, the want for scientificity and mathematical precision had infiltrated the minds of most Englishmen. In 1802, the British sought to draw a map of the subcontinent, based on what they perceived constituted exactitude. Thus the project of the Great Trigonometrical Survey began in 1802 under the British infantry officer William Lambton.

Under the leadership of Lambdon’s successor, George Everest (after whom the mountain was named), the project was made the responsibility of a new body, the Survey of India.

This project was responsible for the measuring of the giant Himalayan mountains, Everest, K2, and Kanchenjunga. The Survey had great scientific impact; it was responsible for one of the first accurate measurements of a section of an arc of longitude, and for measurements of the geodesic anomaly. This inturn led to the development of the theories of isostasy.

Triangulation surveys were conducted on the basis of a few measured baselines and a series of angles. The first baseline to be measured was one near Madras. The survey used triangulation to map territory. Triangulation is the process of determining the location of a point by forming triangles to it from other known points.

The project was at a massive scale. Many new mathematical instruments were made in order to map the terrain. The early surveys used large theodolites and a Zenith sector. Afterwards surveys used more compact theodolites.Everest personally supervised the construction of many instruments due to the fact that it was difficult to get accurate instruments.

The project took over 70 years to complete, and still the government was unable to triangulate all of India. For such a large area, this method was bound to result in inaccurate calculations. Eventually the government gave up on the idea of triangulating all of India, instead they created what they called a “gridiron” of triangulation chains running from North to South and East to West.

Triangulation proved to be a difficult mathematical tool to map India, The colonial government eventually employed other methods as it continued to map the sub-continent.