: How India Calculated the Height of Mt Everest To Amazing Accuracy #IndiaNEWS #Science After years of disagreement, Nepal and China recently reached a consensus on the height of Mount Everest. Until

How India Calculated the Height of Mt Everest To Amazing Accuracy #IndiaNEWS #Science
After years of disagreement, Nepal and China recently reached a consensus on the height of Mount Everest. Until now, the globally accepted height, taken from the 1955 Survey of India, was 8,848 metres. The updated result declared last week was 8,848. 86 metres — a mere 86 cm more than the observation made 65 years ago.
For an order of 8,000 metres, this is a minuscule difference — about 0. 01%. To get an idea of the scale, this would be the equivalent of adding four minutes to a month of 31 days. At a time when advanced technologies like GPS and LiDAR were not around, how did the Indian surveyors of 1955 estimate the height so accurately? And where does the difference of 86 cm come from?
The basic principle: Triangulation
The basic idea involved in measuring a mountain is very simple and very old. It is the same geometric principle that was used even 100 years before the Survey of India, when Everest was first measured and discovered to be the highest mountain peak. As part of the Great Trigonometrical Survey, a 19-year-old Indian mathematician, Sikdar, calculated the height of the Everest (back then, known as Peak XV) in 1852 as 8,840. Just 8 metres short!
Firstly, let us look at how to calculate the height of a pole or a building, without scaling it with a ruler. In the image below, we want to measure the unknown height of the pole (H)To do so, we look at the top of the pole from a certain known distance, from the base of the pole (d). A telescope-like instrument known as a theodolite outputs the angle ? between the top of the pole and the horizontal ground. These are often used by land surveyors near construction sites.
As seen in the diagram, these three lines — (1) the distance between the eye and the pole, (2) the line joining the eye and the top of the pole, and (3) the unknown part of the height of the pole — form a right-angled triangle. Using the relationships between the angles and the sides of this triangle, we can now calculate the unknown segment h. Calculating distances using triangles is known as triangulation.
In a right-angled triangle, the tangent of an angle is the ratio between the length of the side opposite to it and the length of the side adjacent to it. In this case, tan? = h/d. From this, we can get h as d multiplied by tan?,
For example, if d = 100 metres and ? = 60°, then h = 100 X tan 60°. For those unfamiliar with trigonometry, the tangents of angles have fixed values. Tan 60° has a value of 1. 732. You can then calculate h as 173. 2 metres. Suppose the height of the eye-level, x, is 2 metres, then the total height of the pole is 175. 2 metres.
The height of a mountain
Applying the above geometric estimation directly to a mountain is not possible, as we do not know where exactly the base of the mountain lies.

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