<P> SI (cartography) as well as ASI (archaeology), BSI (botany), FSI (forests), FiSI (fisheries), GSI (geology), IIEE (ecology), NIO (oceanography), RGCCI (Census of India) and ZSI (zoology) are key national survey organisations of India . </P> <P> The history of the Survey of India dates back to the 18th Century . "First modern scientific survey of India" was undertaken by W. Mather in 1793--96 on instructions of Superintendent of Salem and Baramahal, Col. Alexander Read . The present Dharmapuri district, Krishnagiri district and North Arcot in western Tamil Nadu were then called Baramahal . </P> <P> Great Trigonometrical Survey (1802--1852) was started by British surveyor Col. William Lambton on 10 April 1802 from St. Thomas Mount in Chennai to foothills of Himalayas. 36 inch huge half ton weight Theodolite was used, which took 57 days to measure the 12 - km base line . This 5 - decade project was completed under Survey General Lt. George Everest in the year 1852 . Surveyor Radhanath Sikdar measured Mount Everest in 1852, with a height of 29,002 feet . Modern measurements indicate the height is 29,037 feet . This is regarded as the beginning of systematic topographical mapping in India and the founding of one of the oldest survey and mapping agencies in the world . </P> <P> The Survey of India, headquartered at Dehra Dun, has 18 Geo Spatial divisions ranging from the prediction of tides to aerial survey . It has 23 Geo - spatial Data Centers spread across India, each catering to the respective administrative area. Surveyors are the back bone of Survey of India . Appointments to Group' A' Civil Stream posts in the Junior Time Scale (Dy Supdtg Surveyor) in Survey of India are made on the basis of competitive Indian Engineering Services examination conducted by the Union Public Service Commission and also through permanent secondment of Army Officers Defence Stream by the Union Public Service Commission . The important posts / grades in Survey of India are in the following order of seniority: Draftsman, Plane Tabler, Survey Assistant, Surveyor, Officer Surveyor, Deputy Superintending Surveyor, Superintending Surveyor, Superintending Surveyor (Non-Functional Second Grade) / Deputy Director, Director / Deputy Surveyor General, Additional Surveyor General, Surveyor General . </P>

Which organisation created the topographical maps of india