The history of land survey in Tamil Nadu: from chains to drones
Your land was likely first measured by a British colonel in the 1800s. A short history of surveying in Tamil Nadu — from the Great Trigonometrical Survey to modern DGPS resurvey.
The survey number on your patta is the end of a long story that started over two centuries ago.
The Great Trigonometrical Survey
Systematic surveying of South India began with the Great Trigonometrical Survey, started in 1802 by Colonel William Lambton with a baseline measured near St. Thomas Mount in Chennai. It went on to map the whole subcontinent.
From chains to total stations
Early surveys used measuring chains, then the theodolite for angles. Today the department uses DGPS (Differential GPS) and ETS (Electronic Total Station) for far higher accuracy.
The modern resurvey
Many districts are now going through a Modern Resurvey — re-measuring villages with current technology and producing fresh, digital maps. This is why old and new survey numbers sometimes need to be matched up.