Google has celebrated the achievements of the 19th century Indian explorer Nain Singh Rawat, the first man to survey Tibet, with a Doodle to mark what would have been his 187th birthday.

Disguised as a Tibetan monk, Rawat walked from his home region of Kumaon to places as far as Kathmandu, Lhasa, and Tawang. 

In the 19th century, the British were hungry for cartographic details of Tibet. But Europeans were not welcome everywhere at that time.

Rawat was prominent among a select group of highly educated and brave local men trained in geographical exploration.

He determined the exact location and altitude of Lhasa, mapped the Tsangpo, and described in mesmerising detail fabled sites such as the gold mines of Thok Jalung.

"He maintained a precisely measured pace, covering one mile in 2000 steps, and measured those steps using a rosary. He hid a compass in his prayer wheel and mercury in cowrie shells and even disguised travel records as prayers," Google said. 

Google's Doodle on Saturday portrays Rawat as he might have looked on his travels – solitary and courageous, looking back over the distances he had walked, rosary beads in hand, and staff by his side.