India in Triangles

by Shruthi Rao, Meera Iyer

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.

Genres: Nonfiction, India

135 pages, Paperback

Published January 1, 2025

Reviews

[Prachipallavi · Rating 5 out of 5]

A great introduction to the Great Trigonometric Survey and the principles used in it. It's definitely intended for a preteen to teenager audience, but I thoroughly enjoyed it as an adult and breezed through it. Worth having on your shelf if you're a parent or just grow interested in this!

[Vinay Kumar · Rating 5 out of 5]

I picked up this book, thanks to an article in the Deccan Herald. The book traces the Great Trigonometric Survey of the 1800s, a scientific marriage of mathematics and civil engineering that mapped the Indian subcontinent. The book is engaging, with hands-on activities, and is particularly targetted towards adolescents. The historical snippets weaved into the technical elements makes the book a good read.

[Deepti · Rating 5 out of 5]

i didn't know about The Grand Survey, the massive exercise by which India was mapped with cm accuracy starting 1800. This was a fun read. I like how the writers also explain how you measure sides with angles and a side of a triangle. The adventures that occurred while doing the survey are also lightly written.

[Deotima Sarkar · Rating 4 out of 5]

There is a GTS tower within 3 kms of where I stay and I always wondered at it being a jut out long thing beside the main road!
Then I got - India in Triangles by Shruthi Rao & Meera Iyer
We all grow up assuming maps to be the taken-for-granted pieces of paper that appear to define a country's shape once and for all. India in Triangles asks readers to peer beyond that outline and see the sheer temerity involved in measuring the land itself. Described to younger readers but never patronizing them, this book recreates the Great Trigonometrical Survey in prose that is brisk, clear, and surprisingly adventurous.
The authors vividly the authors describe the texture of the work: the clank of instruments dragged across rough terrain, the delay of a surveyor waiting for clouds to clear before a sighting, the sheer drudgery of trudging mile after mile with chains to establish a baseline. These details bring a heartbeat to the story, reminding us science is not merely equations but perspiration, mistakes, and tenacity. By situating the math in such human endeavor, the book makes the reader care about what might otherwise have been an intimidating subject.
There is a mix of seriousness and levity in the book beautifully balanced. Diagrams and little exercises buried within the chapters invite the reader to attempt the measurement himself, making theoretical ideas concrete. But the writers never forget the bigger picture: how the enormous survey complemented colonial interests, recast geography, and put India on the world's scientific map.
At 144 pages, it is brief, but it is able to bear the weight of history with stunning clarity. It is not a thick history book or a light adventure novel it straddles the two, keeping advanced science understandable while maintaining the gravitas of the lives entwined in it.
For anyone interested in learning how numbers, angles, and sheer grit sketched out the very shape of India, India in Triangles is an enriching and enlightening read.

[Enakshi J. · Rating 5 out of 5]

India in Triangles is one of those rare non-fiction books that reads like an adventure novel. I found myself completely engrossed in the story of how India was mapped—not just through numbers and coordinates, but through sheer human grit. The idea that a group of surveyors, armed with rudimentary tools and an astonishing method of triangulation, set out to chart an entire subcontinent is mind-blowing. What struck me most was how these men walked thousands of kilometers, often barefoot, braving swamps, mountains, malaria, and even political tensions, all for the sake of precision.
The book balances the technical and the personal really well. It doesn’t overload the reader with jargon but explains the science behind triangulation in a way that feels accessible and even thrilling. There’s something incredibly humbling about reading how the height of Mount Everest was calculated decades before anyone ever climbed it. It made me look at maps and measurements—things I usually take for granted—with a whole new respect.
Overall, India in Triangles is both informative and inspiring. It celebrates unsung heroes of science who didn’t crave fame, but whose contributions changed how we see the world. For readers who love history, geography, or just a well-told tale of determination, this book is an absolute gem.

[Shruti k · Rating 5 out of 5]

What a book! I honestly didn’t expect to enjoy it this much. I picked it up thinking it would be all maps and math—but it’s so much more than that.

This is the real story of the people who literally walked across forests, mountains, and rivers to measure and map India. Imagine trekking through thick jungles, facing wild animals, falling sick in the middle of nowhere, all while carrying heavy equipment… and doing it for years. That’s what these surveyors did. I was amazed at their dedication and how much they achieved without modern technology.

The book talks about something called the Great Trigonometrical Survey—sounds technical, but the authors explain it so well, even a non-math person like me enjoyed it. I didn’t feel lost at all. In fact, I felt like I was *there* with them—setting up instruments, making calculations, and discovering secrets of the land.

There are moments in the book that gave me chills—like when they figured out the height of Everest before anyone else, or when they faced storms and tigers in the wild. It’s not just about geography; it’s about human spirit, science, and adventure.

I also loved how the book doesn't just focus on famous names—we also get to read about the lesser-known heroes who did so much of the hard work. These are the stories we don’t learn in school but I think we must.

The writing is clear, simple, and full of curiosity. It felt like someone was telling me a really good story, not lecturing me with facts.

So if you’re looking for something different—something that’s real, exciting, and makes you see India with new eyes—please pick this up. It’s inspiring, it’s clever, and honestly, it made me proud.

[KAMAL GUPTA · Rating 4 out of 5]

This is a nice little book about a subject I didn’t know and may have never got to know if this book didn’t pop up somewhere and I decided to give it a go.

It gives brief history of Great Trigonometrical Survey done by British during 19th century. It also serves as a little educational book providing the basics of survey mapping using triangulation method.

Should be fun to read specially for kids.

[A K Mishra · Rating 4 out of 5]

Pretty simplistic easy to read version of The Great Arc (John Keay) with some trivias and interesting titbits that tells about the The Great Trigonometric Survey (GTS)...felt more like a magazine long article on it. Could have added more pics of the GTS benchmarks, etc that are still present . Overall a good intro for anyone wanting to know the feat that was GTS.

[Punit Singh · Rating 3 out of 5]

The book presents a very brief history of the Great Trigonometrical Survey of India which was undertaken by the British in the 1800s to map the Indian subcontinent. The book outlines the most basic details of the project and is interspersed with facts in between the main paragraphs.
The book is more of a kids book about the GTS. It will not take more than 2 hours to finish it.

[Deepak Varadaraj · Rating 4 out of 5]

A gentle introduction to the Great Trigonometric Survey and the enterprising men who made it possible.

[Aruna Kumar Gadepalli · Rating 4 out of 5]

The book is about various people who did amazing work of mapping, and survey in India. With examples and illustrations.

[V.Shanmugam · Rating 4 out of 5]

I enjoyed the book. Well written, I have already read about survey. Explained in a simple language.