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Geodesy in India: From Triangulation to GPS
Madhav N. Kulkarni
Department of Civil Engineering
Indian Institute of Technology, Bombay, India
Email: kulkarni@iitb.ac.in
HISTORY OF GEODESY IN INDIA
Over the centuries, along with the numerous political upheavals that the country witnessed, sciences and technology also developed significantly, often with the blessings of the royal armies, leading to several note-worthy discoveries and inventions. The Geodetic sciences formed an integral part of this progress, with spectacular achievements in the fields of astronomy, positioning, mathematics, cartography, and map-making. From the well-documented progress in Geodetic Astronomy, and the surveys for preparing the ancient maps of the country and of the regions over which the great kings ruled, to the precise positioning of points for the great monuments like Qutub Minar, Char Minar, Taj Mahal, and the several ancient cities, forts and magnificent royal palaces, the science of Geodesy progressed gradually through the centuries. Great Indian astronomers, geodesists and mathematicians like Aryabhatta, Bhaskaracharya, Brahmagupta, and others, contributed significantly to the surveying and mapping sciences, through their note-worthy discoveries.
BEGINNING OF MODERN INDIAN GEODESY
Over last two centuries, the ancient science of classical geodesy slowly gave rise to the modern geodesy. With the British Raj came the modern technologies, and the need for geodetic surveys spanning over the entire country. A significant step in this transformation was the establishment of Survey of India (SOI), India’s premier geodetic surveying and mapping agency, in 1767. Started as a modest part of the Royal Engineers, this first technical department of Government of India soon became one of the leading surveying and mapping organizations in the world. The challenging task of carrying out geodetic surveys for mapping one of the largest nations, with diverse terrains, from the snowy peaks of Himalayas to the Gangetic plains, and from the dense rainforests of North-East India to the vast deserts of Rajasthan, was completed by the dedicated geodesists and surveyors of SOI over the years.
The list of the great geodesists and surveyors of India, who contributed to the growth of modern geodesy, includes such legendary figures like Sir (Colonel) George Everest, Colonel Lambton, Brigadier Bomford, and numerous other unnamed Indian surveyors. The completion of the Great Trigonometrical (GT) Triangulation Survey of India, with over 3000 high precision geodetic stations spanning across the sub-continent, was made possible by the dedicated efforts of these surveyors. Precise determination of the height of the highest peak in the world: Mount Everest, based upon this network, is one of the most celebrated achievements of modern geodesy. It is a well-known fact that the peak was named in 1856 after Sir George Everest, a British military engineer who served as Surveyor General of India from 1829 to 1843, during which time the peak was surveyed: a be-fitting tribute to one of the greatest geodesists of all time. Colonel Everest, rightly called the “father of Indian Geodesy”, was the first person to record the location and height of the mountain, then known as Peak XV.
In the field of Geodetic Gravimetry also, India can proudly claim the contribution of many important developments, including the theory of isostacy. It is a tribute to the foresight of such great geodesists that at today the country has an extensive geodetic survey network built on scientific principles. The geodetic survey control net works of India, including the GT Triangulation, high precision leveling, Laplace stations, gravimetric stations, geomagnetic stations, tidal stations, and the more recent Doppler survey stations and Global Positioning System (GPS) stations, established over two centuries of dedicated work, form one of the most extensive and precise geodetic networks in the world. These networks also form the foundation of the precise mapping of the entire country.
CONVENTIONAL GEODESY IN INDIA
Traditionally, the geodetic surveying operations for precise positioning of points on the surface of the Earth for the purpose of mapping the region were very complex, laborious and time-consuming processes. The geodetic aspects of mapping: the determination of the precise positions of few prominent features or survey points in the area, called “control points”, for providing geometric properties- the scale of the map, involved detailed ground survey. The positioning, or provision of “control points”, which controlled the geometric properties and the scale of the map, was carried out using ground measurements of lengths and angles, using theodolites and chains/tapes, which were later replaced by Electronic Distance Measuring instruments (EDMs). Both these terrestrial methods demanded extensive field work, involving large manpower, expenditure, efforts and time; thus making the geodetic surveying and mapping process slow and tedious. In order to ensure inter-visibility between survey stations, often towers: either permanent brick towers (especially in the Gangetic plains) or assembled steel Bilby towers (last used by the author in West Bengal in early 1980s), were constructed. Most national surveying and mapping organizations in the world, including Survey of India, had to put in several decades of labour-extensive work, to complete the geodetic surveys and the topographical mapping of the country, using these classical techniques.
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