which organisation created the topographical maps of india
Survey of India 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.
Contour line Various geological data are rendered as contour maps in structural geology, sedimentology, stratigraphy and economic geology. Contour maps are used to show the below ground surface of geologic strata, fault surfaces (especially low angle thrust faults) and unconformities. Isopach maps use isopachs (lines of equal thickness) to illustrate variations in thickness of geologic units.