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(Economic Observation) How to get to the “new height” at the top of the earth, 88,886 meters?
China News Service, Beijing, December 8, title: How to get the “new height” of 88,886 meters on top of the earth?
Pang Wuji, reporter for the China News Agency
On December 8, China and Nepal jointly announced the most recent elevation of Mount Everest: 8,884.86 meters. This is the third time that China has published altitude data for the highest peak on earth after 1975 and 2005.
The data image shows hundreds of climbers lining up on the way to the top of Mount Everest.
Although 15 years have passed since the last measurement, various technologies are no longer the same, but if you want to get an accurate “height” of Mount Everest, someone still needs to climb Mount Everest. At 11 o’clock on May 27, after going through many difficulties, the Everest Elevation 2020 mountaineering team successfully climbed to the top of Mount Everest, and then 8 team members stayed on top for 150 minutes to complete the task of measuring the top.
Doing his best to climb Everest, measuring and collecting data, he only completed the field task of measuring the height of Mount Everest. Since then, 46 internal employees have been calculating and processing the data non-stop.
How to calculate the “height” of Mount Everest?
First, determine where the “head” and “feet” of Mount Everest are.
Guo Chunxi, director of the Geodetic Data Processing Center of the Ministry of Natural Resources and main responsible for calculating the elevation measurement data of Mount Everest, told the China News Agency reporter that to measure the height of the “great man “Mount Everest, we must first determine where the measurement begins. surface.
The so-called elevation of Mount Everest refers to the height of Mount Everest as a function of the average surface of the sea. Since the shape of the real earth is an irregular sphere, the topography is huge, which brings great inconvenience to represent the shape of the earth, so scientists have introduced the concepts of “geodesic”, “quasi-geoid” and “reference ellipsoid”. Convenient for calculating the measurement results.
The high altitude of the snowy surface of Mount Everest announced this time is a combination of global navigation satellite system (GNSS), traditional triangular elevation observation, regional gravity of Mount Everest, topography, leveling observation data and similar technology from geoid refinement. Media, after many conversions.
How is the height of Mount Everest announced this time different from the previous one?
In 1975, despite the harsh conditions, the final elevation of Mount Everest announced by China was 8848.13 meters, with an error of only ± 0.35 meters.
In 2005, China announced that the elevation of the rock face at the top of Mount Everest was 8844.43 meters, with a measurement precision of ± 0.21 meters, and the depth of ice and snow at the top was 3.50 meters.
The announced altitude of 88,886 meters is higher than the previous two times. The changes are not surprising.
The elevation data for Mount Everest published in 2005 is the height of the summit rock face, which is the “net height” after removing the thickness of the snow and ice cap at the top of Mount Everest. This year, as in 1975, the published data is the elevation of Mount Everest, which includes the height of the maximum snow surface. At the same time, the activity of the tectonic plates in the crust, earthquakes and climate change cause the “height” of Mount Everest to constantly change.
Experts said that in 2020, the scientificity, reliability and innovation of the elevation measurement of Mount Everest will improve significantly.
Guo Chunxi said that in this survey, the Beidou satellite navigation system developed independently by China and with completely independent intellectual property rights was used for the first time to calculate the height of the top of Mount Everest. The Beidou and GPS data were merged, and the precision of the snow surface at the top of the mountain was ± 0.9 cm. Accuracy was improved by 2.1 cm compared to the 2005 results.
Additionally, domestically produced instruments are responsible for the 2020 elevation measurement of Mount Everest. This time, domestic and imported GNSS receivers were used together at the peak to obtain the same accuracy. It is worth noting that this year, the domestic-made gravimeter reached the top for the first time to measure the gravity value of the peak, and at the same time integrated the domestic-made aerial gravimeter measurement data, greatly improved measured the accuracy of the gravity-like geoid model on Mount Everest.
The data processing work of the 2020 Mount Everest elevation survey has carried out a multi-level comparison of results to ensure the reliability of the final publication results, including: comparison of results from different survey software GNSS data processing at home and abroad; different observing technologies (GNSS upper peak, triangle Comparison of Rendezvous Survey results); the comparison of the calculation results in 2020 and the calculation results in 2005; the comparison between the calculation results of China and Nepal.
It is worth noting that this time China and Nepal jointly built a global elevation benchmark for the Mount Everest region for the first time, laying a solid foundation for the two countries to jointly publish the new height of Mount Everest based on the point of global elevation reference.
Guo Chunxi said that China’s national elevation datum is roughly based on the mean sea level of the Yellow Sea as a unified base, while Nepal uses the sea level of the Indian Ocean as its datum. There are differences between the two. Taking these differences into account, China and Nepal have jointly constructed a global elevation reference point for the Mount Everest region, which is equivalent to “using the same ruler to measure the height of Mount Everest.” (End up)
