The journey to the summit of Mount Qomolangma is dangerous, and the organizers invested huge manpower, material resources and financial resources into the effort.
Addressing why modern technologies such as satellite remote sensing images or GPS positioning systems that are widely available cannot be used to directly measure the height, Dang said that satellite remote sensing images are mainly used for surface detection. Heights can only be measured with a margin of error of two meters, and only from the top of the snowpack.
Other ways to measure the mountain have been discounted as being too dangerous or unfeasible, such as measuring by aircraft or drone, due to operating limitations and the harsh conditions above a peak over 8,000 meters. It is felt that the most accurate measurement can only result from sending a team to the peak.
There are two main methods of height measurement. The first is by using triangulation where correcting for gravity, atmosphere and other aspects allows a height to be obtained. The second method is through GPS satellite geodesy, initially used in 2005, but this requires someone to place a GPS receiver at the summit.
The 2020 expedition is using GNSS satellite survey, precision leveling, photoelectric ranging, snow-deep radar measurement, gravity measurement, astronomical measurement, satellite remote sensing, quasi-geoid refinement and other traditional and modern mapping technologies. Using China-made equipment has been a breakthrough this time. “In addition to aerial gravimetry, the rest is still based on technologies adopted in 2005, but this time we used a lot of domestic equipment,” Dang said.
GNSS satellite measurements consist of four systems: BeiDou (China), GPS (US), GLONASS (Russia), and Galileo (EU). “In 2005, GNSS satellite measurements relied mostly on GPS. This year, we will refer to the four global navigation satellite systems concurrently and mainly depend on data from the BeiDou Satellite Navigation System,” said Li Guopeng, head of the first Geodetic Surveying Brigade under the Ministry of Natural Resources, at a press briefing before the project launched.
Another innovation is the first use of aerial gravimetry for the measurement attempt. Dang said that the accuracy of the measurements could be about 30 to 40 percent higher.
“The height we see when we look at it is not its true height,” Zhang Yanping, leader of the 2005 survey team said during an earlier interview with the People’s Daily. “Because the earth is elliptical, and the starting point of your sight is the point at your feet, not the point at the foot of Mount Qomolangma, so you see the summit as lower than its true height.” Therefore, the prerequisite for precise measuring of the elevation of Qomolangma is to find the zero elevation point at the foot of the mountain.
China takes the average sea surface of the Yellow Sea at Qingdao tidal station in East China’s Shandong Province as the zero elevation point. “One can imagine a sea level, which is a curved surface, with all the gravity values equal on the surface. This is the zero elevation starting surface. There is a gravity value on the surface where the zero elevation point at Qingdao is located. The same gravity value below Mount Qomolangma, once found, could be taken as the starting surface then,” Dang said, adding that it would be more accurate.
Despite the significant advantages of aerial measurements, it is difficult for an aircraft which would take the measurements to operate safely that high. It is more suitable for low altitude areas.
“The peak is over 8,800 meters, and the aircraft is flying at an altitude of 200 meters above it, which is very dangerous. The north face of Mount Qomolangma is complex in terrain, with an unstable climate. Experienced pilots pointed out the dangers of attempting it, which might even cause the aircraft to crash,” Dang said.
After the proposal was rejected, Dang’s team did not give up. As they learned later that the China Center for Aerial Geophysical Prospecting and Remote Sensing of Natural Resources would be able to complete the task, they worked on a detailed technical plan for six months. After it was reviewed by experts, it was included in the overall project plan for the measurement.
There is only one month a year in which there is a weather window to climb Mount Qomolangma. As summiting the mountain becomes more popular, this is why we see pictures of people stuck in “traffic jams” as occurred last year on the Nepalese side. Eleven climbers died in 2019, with much of the blame pointed at inexperienced climbers and companies eager to make money.
The Chinese survey team did not want to take a chance on the weather for this attempt even though unexpectedly they found themselves alone on the mountain. The Meteorological Bureau of the Tibet Autonomous Region set up a 16-strong meteorological support team divided into two support service groups to provide meteorological detection and weather forecasts.
In order to ensure communication, the Tibet Autonomous Region Communications Administration organized China Mobile Tibet Branch to implement the “5G on Mount Qomolangma” plan. Netizens were able to watch real-time video transmissions from the base camp and the moment the surveyors reached the peak and started their measurements. Transporting eight tons of network construction equipment and life support materials by yak, five 5G base stations were built at the 5,300 meter base camp, the 5,800 meter transition camp and at the 6,500 meter advance camp, providing gigabit broadband and special line access. Furthermore, three 4G base stations were built along the route. Specialist staff was stationed at the high altitude camps to ensure the network operated smoothly with reliable data transmission. Data obtained would be sent back to the Geodetic Data Processing Center of the Ministry of Natural Resources in Xi’an in real time.
When the team of eight climbers finally reached the summit, they had to work quickly. They finished the positioning of the equipment and other observations within two hours. But the result will not come immediately. It is expected that the final height will be released in two or three months. “We still need to be patient and wait for the final result,” said Dang.
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