How was the 8845.13 meters of Mount Everest measured?
8848.13 meters - the Everest elevation that has been used since the 1970s, is about to be refreshed, but how is this figure determined, and the technologies and methods used in China during the Mount Everest survey, There are not many people who must know.
World Everest Measurement Statistics from 1848 to 1968
The First Determination of Everest Heights in the 8840m History of India from 1848 to 1850
From 1880 to 1883, the result of 1902 published in India was 8882 meters. This data is also used by our country in the past.
From 1952 to 1954 in India (in Nepal) 8847.6 meters. This data is the snow surface elevation of Mount Qomolangma.
China's 8849.9 meters twice test from 1966 to 1968
As shown in the above table, although India has improved its measurement plan, techniques and methods used during the three measurements of Everest altitude, it is far from the Everest because of the lower elevation of the elevation control station. The measurement plan is poorly detailed, so the measured data is less accurate.
In the two trials of China in the 1960s, both the accuracy of observation data and the rigor of the theory were higher than those measured abroad. However, there are still some measurement conditions and factors that cannot be taken into consideration in these two test tests, and therefore the accuracy of the measurement results is affected.
Therefore, in July 1975, China’s surveying and mapping workers again measured the elevation of Mount Everest with the cooperation of the national mountaineering team. In the entire measurement, triangulation, wire measurement, leveling, trigonometric leveling, astronomical measurement, and gravity were comprehensively used. The results of measurement, astronomical leveling and vertical temperature gradient measurement have established a reliable measurement and control basis for the accurate determination of the height of Mount Everest. Based on the second-class triangular lock established during the test, it placed a triangular lock and a microwave distance measuring wire along the East Rongbuk Glacier and the West Rongbu Glacier, and increased some astronomical and gravitational points. A benchmarking point (represented below by the symbol A) is also set at 13.6 km from Everest and at an elevation of 5680 m, which is used as the starting point for determining the height of Mount Everest. Nine stations were selected near this standard. They were distributed in a fan-shaped area centered on Mount Everest. The distance to Mount Everest was 8.6-21.2 km and the elevation was 5600-6240 meters.
The trigonometric leveling method was used to transfer the elevation of point A to 9 stations. Then the 9 stations were used to measure the horizontal and vertical angles of the target at the same time using the method of trigonometric elevation. According to the horizontal angle, the horizontal position of Everest can be determined and the horizontal distance from each station to Everest. According to the principle of trigonometric level measurement, the height difference between each station and Mount Everest is determined from these elevation angles and horizontal distances, and finally the strict theory is established. Based on the above data, astronomical and gravimetric data were used to calculate the height of Everest, using the height of the earth and normal height as the transition.
Compared with the past several times at home and abroad in the history of Mount Everest, compared to the determination of Mount Everest in 1975, its observation techniques and methods were advanced at the time, and the types of measurement data used were also the most. The distance between the elevation and the Mount Everest is the best. The theory of the elevation calculation is the most rigorous, especially the 3.52 m red metal target erected at the top of the Mount Everest. The alignment error is small, and it is in the elevation measurement result. The snow cover thickness (0.92 meters) was deducted, which was actually measured by the mountaineers at the top of Mount Everest. Therefore, it can be said that before the release of the re-test results of Mount Qomolangma on May 22, 2005, the 8845.13 meters of Mount Everest measured in 1975 is still the most accurate.
(Source: China National Bureau of Surveying and Mapping, edited by Wikipedia Knowledge Magazine)
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