Charting the shape of India

In an age when vast swathes of the world remained unmapped and mysterious, maps were more than navigational tools—they were instruments of power, knowledge, and ambition. In the late 18th century, as European empires scrambled to define and dominate distant lands, accurate cartography became a prized asset. It was against this backdrop that James Rennel undertook the first large-scale survey of India in 1782, producing the Map of Hindoostan through rudimentary route surveys. Rennel’s efforts were merely the prologue to a far more audacious endeavour: the Great Trigonometrical Survey (GTS) of India, an epic scientific undertaking that spanned nearly a century. In their new book India in Triangles, authors Shruthi Rao and Meera Iyer chronicle this extraordinary project.

Commissioned by the East India Company in 1802, the GTS was born out of imperial necessity. As the Company extended its dominion, the need to measure, classify, and control the land became ever more urgent. The GTS sought to map the entirety of the subcontinent—including the vast and forbidding Himalayas—using cutting-edge trigonometric methods that, for their time, represented the pinnacle of surveying science. “We split the story into easily understandable chunks, provided a lot of context at every turn, so that it could be easily understood,” says Rao. “We tried to ensure the main narrative flows like a story and provided boxes or sidebars for those who would like to learn more.”