Survey Instruments in India
Astronomical observations performed several key functions within colonial survey sciences. Portable instruments could be used to find local time, orient field stations to true north, and fix longitude and latitude by tracking celestial motions.
In India in particular, this highly accurate mapping work then anchored local revenue surveys that formed the basis for colonial tax regimes.
Astronomy on the move
Image 1 shows a ‘Russian’-style transit instrument that has been carefully packed into two large boxes for transportation into the field.
This instrument was one of a pair ordered in 1869 for use in the Great Trigonometrical Survey.
In 1862 the Surveyor General of India, Andrew Scott Waugh, had declared the results from the entire eastern section of the survey to be sub-standard “on account of the defective state of instrumental equipments”, and ordered it re-done “with appropriate apparatus.”
This instrument was used to determine local time from the motion of the stars. This could then be compared with Greenwich time transmitted via telegraph, the time difference giving the site’s longitude.
This instrument therefore worked within a complex imperial network of telegraph lines and survey outposts.
Its size and weight also reminds us that these networks could not function without the labour that made such tools “portable.”
Image 1: ‘Russian’-style portable transit instrument, by Thomas Cooke & Sons, York, 1869 (Wh.6641)
Revenue surveying
At a local level, British tax collectors in India conducted surveys to settle land rights and assess revenues.
This called for simple survey instruments like the 66-ft chain shown in Image 2, used to measure boundary lengths; and the plane table shown in Image 3, used for basic sketching of field sites.
Much of the labour for these surveys was conducted by trained youths of mixed European-Indian parentage recruited from orphanages and paid one-sixth of a military surveyor’s allowance.
Image 2: 66-ft steel chain, by Chesterman, Sheffield, c. 1850 (Wh.2722)
Image 3: Plane table and alidade, by Cary, London, c. 1900 (Wh.2528)
Joshua Nall, ‘Survey Instruments in India’, Explore Whipple Collections, Whipple Museum of the History of Science, University of Cambridge, 2020.