Trigonometry for a hill top

What does a mountain peak in Kodagu have to do with trigonometry? Thadiyandamol, the highest peak in Kodagu at 5,730 feet, has gone into the surveying history of the world as one of the main stations in the Great Trigonometrical Survey of India, conducted between 1802 and 1862.

During this survey, the subcontinent was meticulously surveyed and mapped, and the heights of Mount Everest, K2 and many lesser peaks were calculated. Having read about the Great Trigonometrical Survey, we wanted to trek up the historic Thadiyandamol peak. It was only when we were well into the trek, we realised how difficult it must have been for those surveyors 200 years ago.

When the surveyors came to Thadiyandamol in 1810, the place was an impenetrable jungle. The Nalknad Palace which is at the base of the hill must have been a haven for them and their numerous helpers. Built in 1794, this two-storey tiled palace in the dense rainforest was the refuge of the kings of Kodagu, who were constantly at war with Hyder Ali and Tipu Sultan, and later with the British. It was from this palace that they carried out their manoeuvres against the enemy.

After the decisive Fourth Anglo-Mysore War in 1799 when Tipu Sultan was killed, the vast territory of Mysore fell into the hands of the East India Company. The Company wanted it to be surveyed. Colonel Lambton, a trained surveyor, was appointed by Lord Wellesley for the purpose. Lambton, a stickler for precision and accuracy, had great respect for new scientific methods.

Lambton began a preliminary survey in 1800 with the base line near Bangalore, which measured 7.4321 miles. A chain made of blistered steel was specially brought from England for this purpose. The chain had 40 links and its total length was 100 feet.

Lambton also procured many quality surveying instruments and several theodolites — delicate surveying instruments with rotating telescope which could measure the horizontal and vertical angles, from England. The ship carrying these delicate instruments was captured by the French, who, after inspecting the instruments, repacked them and allowed the ship to carry them to India.

After the preliminary procedures and preparations, the Trigonometrical Survey began in 1802 from Madras. In 1804, another base was measured near Bangalore, from which a series of triangles were carried across the peninsula to Mangalore. One of the stations for the Great Trigonometric Survey was Thadiyandamol, whose height was determined to be 5,682 feet by trigonometrical calculations.

First of its kind
In 15 years, Lambton covered the whole of peninsular India from Goa in the West to Machilipatnam in the East; and from Kanyakumari in the South to Bihar in the North, in triangles, covering an area of 1,65,342 sq miles. After Lambton’s death in 1818, Colonel Everest and others continued the survey, until the whole of the Indian subcontinent was surveyed, by 1860. No other country in the world had been surveyed so thoroughly and meticulously.

As we neared the Thadiyandamol peak, the dense forest gave way to grasslands and the gradient of the trail increased drastically, making it harder to climb up. Wild flowers dotted the grasslands. We still had a long way to go. The last stretch of the trail was the hardest and gave a feeling of climbing a wall. We thought of all those intrepid surveyors and porters carrying the heavy chains and theodolites, and trudged on.