Today any adventure or holiday travel begins with collection of relevant maps. But that was not so 250 years ago. In 1757, after their victory in the Battle of Plassey, the English East India Company (EICO) was first granted a zamindari by Mir Jaffar and by 1765 the nominal Delhi emperor granted them the Dewani of the subah of Bengal.
Events were moving in a manner which ultimately transformed the EICO into a king. And they knew almost nothing about their new acquisition. This made it necessary for them to draw a map of their new possessions and to achieve that they created a survey department and appointed James Rennell as the first Surveyor-General of India in 1767.
The headquarters of the Survey of India (SoI) and surveyor-general were at Dacca, now in Bangla Desh. Rennel produced two major maps of India that established his, pre- eminence in the world of geographers. The first, “Bengal Atlas” was in 1781; it contained 21 maps and was considered a work of great importance from strategic and administrative point of view.
The second one, “Memoir of a Map of Hindustan”, a great work on Indian geography, was brought out in 178 3, and was the first approximately correct map of India. It was accompanied by a memoir containing a full account of the plan on which the map was executed and of his authorities. G V Joshi writes on science issues Since then surveyors from SoI have surveyed and mapped each and every part of the country and the maps drawn by them have played a very valuable role in the nation building and development activities of modern India.
SoI is celebrating the occasion. However, a common man in India cannot buy a map of his town or city in any book shop or a tourist office, as these are not made available by the authorities of SoI for security reasons. But now there is some hope for those with computers and access to Internet. According to Dr Harsh Vardhan, Union Minister of Science and Technology and Earth Sciences, Government of India, “There is an existing law which says that any information which is compiled with public money should be made available to the public.”
Dr Harsh Vardhan was surprised to learn how difficult it was to buy maps, and he requested the SOI to work out a programme to enable people to have free access to maps after proper identification. As a result SoI has recently declared the launch of the Nakshe Portal, a new web portal that will provide free download of Survey of India’s topographic maps. The website contains a set of 3,000 maps available to Indian citizens. The SOI will subsequently release another batch of around 700 maps shortly. The total country is covered by 5,700 maps, of which around 2,000 cannot be accessed by the public due to security issues.
The ones which have been made available are those which do not have boundary issues and do not have data on sensitive installations. Nevertheless anyone, anywhere in the world with an internet link can see any spot on Earth through Google Earth. He can even spot his house. A tourist visiting India needs a map more than others, but as of today, they are not available to him. There is also some confusion about who is a resident, a citizen or an Adhaar card holder. It is felt that maps not involving any security risk should be available to anyone who wants them easily, without any paper work and administrative procedure.
Along with Survey of India, Survey of Pakistan and Survey of Bangla Desh are also celebrating the event . As everyone knows, Survey of Pakistan was created after partition in 1947 and Survey of Bangladesh was created after break up of Pakistan in 1971. One of the greatest contributions of SoI is its role in the determination of the shape and dimensions of Earth. That the Earth is an oblate spheroid (like an orange) was well established by this time.
Newton, known for his theory of gravitational attraction, had proved it through a simple proof. In other words, Earth’s radius along the equator was slightly more than its radius along the poles. But the accurate value of the equatorial radius on of Earth and the question, ‘how much more than the polar radius’, remained unanswered. The determination of the distance between two points on earth separated by one-degree of latitude along the same line of longitude gives the surveyors some idea about the curvature of the earth in that region.
For a perfect sphere, it should be the same everywhere. But for an oblate spheroid, this would be less near the equatorial latitudes than at the poles. It is also possible to work out the radius of the earth from this in both directions from this data. Some work to determine the radius was carried out in France, but the results were ambiguous. Col Lambton followed by George Everest, two great surveyors from Great Trigonometrically Survey (GTS) under SoI determined the length an arc of meridian along 78* East longitude from Tirunalvelli in Tamil Nadu to Banog Hill near Mussoorie in Uttrakhand.
At that time, the work was justified as part of an attempt to provide an accurate base for systematic topographic and revenue surveys of India, but it was also part of an attempt to answer one of the thorniest scientific problems of the day, the determination of equatorial and polar radius of Earth. The result of Lambton/Everest work, also confirmed that Newton was right.
The radii determined by Everest and his followers were used in determining the shape of Earth and they are still being used by SoI. Many more measurements of 1 degree arc were carried out subsequently. Although Global Positioning System (GPS) is much quicker than the methods used for mapping then by Survey of India, the mathematics used by GPS is based on the knowedge of the dimensions of Earth and therefore the contribution of surveyors from SoI is very important and should be recognised as a major achievement.