Survey of India

Also called: SoI · Topic: Maps and Map Scale · NCERT: Class 6, Ch 1 "Locating Places on the Earth"; Class 11, Ch 1 "Introduction to Maps"; Class 11, Ch 5 "Topographical Maps"

Meaning

The Survey of India (SoI) is India's national mapping agency. It was set up in 1767 and makes topographical maps (detailed maps showing land height, rivers, roads and settlements) of the whole country at 1:250,000, 1:50,000 and 1:25,000. It works under the Department of Science and Technology (DST) [2].

It is the oldest scientific department of the Government of India [2][4]. Almost every official map in India is built on its survey points, boundary lines and toposheets.

Explanation

Origin: from Company surveyors to a national agency

• SoI grew out of colonial mapping.
• East India Company surveyors in the 18th century explored and mapped land that had never been mapped before [2].

• The Company needed maps to collect land revenue, move troops and fix borders.

• 1767 is the start date.

• That year Major James Rennell was made Surveyor General of Bengal, and SoI traces its origin to this post [3].
• Intensive topographical surveys (careful measurement of land height, rivers, roads and settlements on the ground) began that year.
• This work led to the map of Hindustan in 1785, which is linked with James Rennell.

Great Trigonometrical Survey (GTS) and the Pundits

• Triangulation (fixing exact positions with a chain of triangles):
• A baseline (a straight line on flat ground) is measured very carefully.
• Angles to distant hilltops are measured from each end of the baseline.
• Each new triangle uses one side of the triangle before it, so the chain spreads across the country.

• Result: exact positions and heights for thousands of points.

• GTS facts:

• Started in 1802 at Madras by William Lambton.
• Its main line was the Great Arc, a north–south chain of triangles along roughly the 78° E meridian, running from South India towards the Himalaya.
• It was carried on by George Everest, Surveyor General from 1830 to 1843.
• Around 1852, Radhanath Sikdar, an Indian mathematician and "computer" (a person who did survey calculations), worked out that Peak XV was the world's highest peak. It was named Mount Everest in 1865.

• SoI says its GTS series running north–south and east–west are "some of the best geodetic control series available in the world" [2][4].

• Pundits (Indian surveyors trained by the British in the 1860s to map Tibet in secret, because foreigners were not allowed in):

• They counted their steps on prayer beads. Each bead stood for a fixed number of paces.
• They hid their instruments, for example inside prayer wheels.
• Nain Singh Rawat fixed the position of Lhasa.

How SoI is organised today

Feature	Fact
Status	Oldest scientific department of the Government of India [2][4]
Role	Principal mapping agency of the nation [2][4]
Headquarters	Dehradun, Uttarakhand (Hathibarkala Estate), where the Surveyor General's Office works [2][4]
Parent body	DST, Ministry of Science and Technology [2]
Head	Surveyor General of India
Growth	5 Directorates in 1950 → 22 Directorates at present [2]. An older DST page gives 18 [4]
Digital work	3 Digital Centres, set up in the late 1980s, prepare Digital Topographical Databases for the whole country [2][4]
Training	National Institute for Geo-informatics Science & Technology (NIGST) [2]
Policy	Works under the National Geospatial Policy 2022 and the 2021 guidelines on geospatial data [2]

Main duties and products

• Map series (a set of maps made at the same scale, style and specifications, whose sheets fit together side by side):

• SoI toposheets at 1:250,000, 1:50,000 and 1:25,000 cover all of India as many small sheets that join without gaps.

• Other duties [4]:

• It maintains geodetic control, the network of exactly fixed points on which all other maps are built.
• It sets the standard spelling of geographical names.
• It shows India's external boundaries on maps.
• It certifies how the boundary is drawn on maps printed by other agencies.

• It gives tide predictions for 44 ports.

• Geodetic datum (the model of the earth's shape that a map uses to give latitude and longitude):

• Old SoI sheets use the Everest spheroid (1830), which fits the Indian region well. A spheroid is a slightly squashed sphere that stands in for the earth's shape.
• Open Series Maps use WGS-84 (World Geodetic System 1984), the same global datum that GPS uses.
• The same spot can have slightly different coordinates on the two, so a GPS reading must be converted before you plot it on an Everest-datum toposheet.

Where it occurs

• Headquarters: Dehradun, Uttarakhand (Hathibarkala Estate) [2][4].
• Coverage: the whole of India, mapped at 1:250,000, 1:50,000 and 1:25,000.
• Historic survey lines:
• The GTS began at Madras (1802).
• The Great Arc ran along about 78° E, from South India towards the Himalaya.
• Peak XV (Mount Everest) in the Himalaya was identified through GTS calculations.

• Lhasa in Tibet was located by the Pundit Nain Singh Rawat.

• Coasts: tide predictions for 44 ports [4].

• How it is used in India:
• Its digital topographical databases come from 3 Digital Centres [2][4].
• It trains staff at NIGST [2].
• Under the National Geospatial Policy 2022 [2], its data supports planning, disaster management and infrastructure.

Don't confuse with

• NATMO (National Atlas and Thematic Mapping Organisation): based in Kolkata. It began in 1956 as the National Atlas Organisation and was renamed in 1978. It makes national atlases and thematic maps (maps on a single subject such as rainfall or soils). SoI is in Dehradun and makes topographical maps. Both come under DST.
• Surveyor General of Bengal vs Surveyor General of India: Rennell's 1767 post was Surveyor General of Bengal [3]. Today the Surveyor General of India heads SoI.
• Great Trigonometrical Survey (1802) vs founding of SoI (1767): the GTS started 35 years after SoI's origin. It was begun by Lambton, not Rennell.
• Everest spheroid vs WGS-84: the Everest spheroid (1830) is a regional datum used on old SoI sheets. WGS-84 is a global datum used by GPS and Open Series Maps.

Prelims Hooks

• SoI was set up in 1767. It is the oldest scientific department of the Government of India [2][4]. HQ: Dehradun. Parent: DST [2].
• Map of Hindustan (1785) → James Rennell, who was made Surveyor General of Bengal in 1767 [3].
• GTS → 1802, Madras, William Lambton. Method: triangulation along the Great Arc (~78° E).
• Radhanath Sikdar identified Peak XV as the highest peak (~1852). It was named Mount Everest in 1865, after George Everest (Surveyor General 1830–1843).
• Match the HQ (trap): SoI → Dehradun. NATMO → Kolkata. Both are under DST.
• SoI toposheet scales: 1:250,000, 1:50,000, 1:25,000. Open Series Maps use WGS-84, not the Everest spheroid.

Mains Points

• Mapping served colonial power.
• The East India Company surveyed land to collect revenue, move troops and fix borders [2].
• The GTS and the secret Pundit missions into Tibet show science working for empire.

• The same work left India with world-class geodetic control [2][4]. (GS-I)

• Indian contribution was hidden by colonial naming.

• Radhanath Sikdar's calculation of Peak XV and Nain Singh Rawat's fix of Lhasa were key pieces of scientific work.

• Yet the peak was named after Everest, not Sikdar.

• Paper to digital mapping.

• SoI's Digital Centres (late 1980s) started building digital topographical databases [2][4].
• The National Geospatial Policy 2022 [2] made geospatial data easier to get for planning, disaster management and infrastructure.
• The move from the Everest spheroid to WGS-84 lines Indian maps up with GPS. Old and new sheets must be converted carefully, or land records and boundary work can go wrong. (GS-III)

Related concepts

• Map series
• Great Trigonometrical Survey
• Pundits
• Geodetic datum
• National Atlas and Thematic Mapping Organisation

Read more

• The Survey of India and modern mapping institutions