Step into the boots of fearless surveyors as they trek across forests, mountains and monsoons?facing disease, wild animals and gruelling terrain?to chart the subcontinent with astonishing precision. This was the Great Trigonometrical Survey, an ambitious mission to map India using triangulation?a brilliant method that helped them measure every inch with accuracy. Along the way, they calculated the height of the world?s tallest mountain and revealed the true shape of the earth. Packed with adventure, ingenuity, mishaps and the unsung heroes of science, this is the epic true story of mathematics, grit and discovery.