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…