Restart Everest "height" measurement
China News Weekly reporter / Yang Zhijie
Issued in 2020.5.18 total issue 947 "China News Weekly"
On May 6, the Everest Base Camp at an altitude of 5,200 meters ushered in good weather. The weather was blue and the visibility was high. You can clearly see Everest covered by snow all the year round.
This is also a good time to climb Mount Everest. Yuan Fudong stuffed his sleeping bag into a mountaineering bag full of luggage. The remaining 30 companions also put on red mountaineering uniforms, wearing hats and sunglasses, and holding trekking poles. At 1:30 in the afternoon, everyone came to the open space to gather. After a brief ceremony, more than 30 people cheered each other, lined up with confidence, and headed towards Mount Everest.
They are not ordinary climbers, but the 2020 Everest Height Survey Mountaineering Team, which is composed of professional mountaineers and the surveyors of the No. 1 Geodetic Survey Team of the Ministry of Natural Resources (abbreviated as the National Surveying First Team). They will carry GNSS (Global Satellite Navigation System) receivers, gravimeters, snow depth radars, meteorological measuring instruments and target targets to the summit of Mount Everest to accurately determine the height of Mount Everest.
The weather window suitable for climbing Mount Everest is preferably free of strong winds and heavy snow. According to the local weather forecast, there are three window periods in May. The surveying mountaineering team set off on May 6 to catch up with the first window period on the 12th. According to the plan, they will reach the 5,800-meter camp on the 6th and the 6,500-meter the next day. After two days of rest, they will start to attack the summit.
But the plan is to be more thorough, to challenge the highest peak of the earth, and have to "eat by the sky." Just one day later, the situation changed suddenly. On May 8th, due to the weather, the climbing route snowed deeper, and there was a danger of snow drift. All mountaineering team members had to return to Everest Base Camp in batches to rest. This means that the time to climb the summit of Mount Everest has to be delayed.
All team members are currently waiting for the next window period. The world is also waiting for a new height of Mount Everest.
"Measuring height" for Everest
Mount Everest is located in the eastern part of the border between China and Nepal and is the highest mountain in the world. In the past few decades, the altitude of Mount Everest widely recognized by the world is 8848 meters. In 2005, the former National Surveying and Mapping Bureau measured the elevation of the rock face at the summit of Mount Everest at 8844.43 meters. This year's survey is the second time that China's surveying and mountaineering team started the survey of the height of Mount Everest after the height of Mount Everest was announced twice in 1975 and 2005.
"There are two main reasons for re-evaluating the height of Mount Everest. The first is that the height of Mount Everest must have changed. Second, the technology of Mount Everest has also made a big leap, and the new technology can significantly improve the accuracy of Mount Everest." 2020 Beads Dang Yamin, leader of the Coordinating Group for Peak Height Measurement Technology and a researcher at the Chinese Academy of Surveying and Mapping, told China News Weekly.
Dang Yamin explained that there are two types of changes in the height of Mount Everest. In the long run, this mountain range is still slowly rising at a rate of 4.4 mm per year, which means that it will rise by 4 cm in 10 years and more than 13 cm in 30 years. If the measurement accuracy of Mount Everest is about 10 cm, then the height of Mount Everest needs to be re-measured in 20 to 30 years. "
In the short term, an earthquake may also affect the height of Mount Everest. In 1934, an earthquake occurred in Nepal. The epicenter was only 9.5 kilometers away from Mount Everest, which had a significant impact. The first peak was "shortened" by about 63 centimeters. In April 2015, Nepal suffered another 8.1 magnitude earthquake that occurred 200 kilometers away. Some scholars used satellite remote sensing data to study the height of Mount Everest, and the results show that the height of Mount Everest has decreased to some extent. However, remote sensing means have low accuracy in monitoring the height of Mount Everest, and accurate determination of Mount Everest requires the use of high-precision geodetic observation methods.
"At present, the precise impact of the 2015 Nepal earthquake (on the height of Mount Everest) is still unknown. As one of the sovereign states of Mount Everest, we have the responsibility and obligation to measure the accurate data of Mount Everest's elevation and give the world an accurate answer." Dang Ya The people said.
Geodeticist Chen Junyong once quite vividly described the reason for measuring Mount Everest, "Parents should regularly measure the height of their growing children, it is reasonable. Humans must continue to understand nature in depth, and the Chinese must constantly Know your country deeply. "
Dang Yamin also pointed out that the height measurement of Mount Everest not only measured the latest height of Mount Everest, but also observed a large amount of measurement data for the "reference transfer" of altitude in the Mount Everest region. The results of these data can also be used in the field research of geodynamic plate motion in Qinghai-Tibet region and the impact of earthquake on Mount Everest. Accurate data such as peak snow depth, meteorology, wind speed and glacier monitoring will provide first-hand information for natural resources monitoring and ecological environmental protection of Mount Everest and its surrounding areas.
Climbing Mount Everest is not an easy task, and the journey is divided into 6 meeting points in detail. According to the original plan, on May 6, the survey team members set off from Mount Everest Base Camp, passed the Rongbu Glacier and the East Rongbu Glacier, and reached the middle camp at an altitude of 5800 meters. Climb another 700 meters to reach the forward camp at an altitude of 6,500 meters. The oxygen in the camp is very scarce, the altitude reaction is strong, and the players need to rest. Next, the survey team must reach Camp No. 1 at an altitude of 7028 meters, Camp No. 2 at an altitude of 7790 meters, Camp No. 3 at an altitude of 8300 meters, and finally sprint to the summit of Mount Everest depending on the weather.
At the peak, there is not enough time left to measure the mountaineering team. In 2005, Chen Bangzhu, then director of the State Bureau of Surveying and Mapping, once mentioned that because of the peak climate and harsh natural conditions, mountaineering team members should not stay longer than 2 hours. At that time, they completed the collection of measurement data at the peak, the erection of the target, and the scanning of the snow depth by the snow radar. They stayed for nearly 2 hours, and it took only 40 minutes to actually collect the measurement data.
Recently, due to the weather, the summit time will be delayed from the originally scheduled May 12-14. But preparations for mountaineering have not stopped. According to reports, according to the plan, on May 11, the road construction team will lay the rope to an altitude of about 8600 meters and return to the assault camp at an altitude of 8300 meters. On May 12, weather permitting, road construction team will repair the peak route. At the same time, the 12 guides will depart from the No. 1 camp at an altitude of 7028 meters, transport the materials to the assault camp, and do the work of the road repair team.
International competition
Prior to this, Chinese surveying and mapping workers have conducted 6 large-scale surveys and scientific investigations on Mount Everest. In addition to China, other countries have never stopped exploring the world ’s highest peak, and have repeatedly measured the height of Mount Everest.
In 1856, the British surveyor Sir George Everest led the team to break the mysterious veil of Mount Everest and announced the elevation of Mount Everest for 8840 meters for the first time.
Entering the 20th century, the elevation measurement of Mount Everest aroused the interest of more countries. In 1954, the Indians reached the summit and calculated a height of 8848 meters. In 1966 and 1968, China had twice teamed up to measure the height of Mount Everest, but neither announced the results. In 1975, during the third measurement of the height of Mount Everest, the national survey team calculated the elevation of the summit of Mount Everest to be 8,884.13 meters. This is almost the same as the data calculated by India, both of which measure the snow elevation of Mount Everest.
In 1992, Italian scientists and mountaineers came to China and measured the height of Mount Everest at 8846.50 meters. In 1999, with the support of the National Geographic Society, an American Everest expedition team fixed the GPS device on the highest bedrock and calculated that the height of Mount Everest was 8850 meters, and the highest peak in the world grew a few meters higher.
The most recent measurement was in 2005. China measured the height of the rock face of Mount Everest at 8844.43 meters, which was recognized by UNESCO.
But as of now, the height of Mount Everest is still internationally indifferent. Nepal, on the other side of Mount Everest, only agrees that the height of Mount Everest is 8848 meters. This data was measured by India in 1954.
The New York Times reported that geologists disagree on how to calculate the height of the mountain: should the snow on the top of the mountain be included? Or should the bedrock of the mountain be drilled during the measurement?
Nepal chose the former. As we all know, climbing Mount Everest can be climbed from the northern slope of China or the southern slope of Nepal. Climbing Mount Everest has already formed a complete industrial chain in Nepal. China News Weekly reported that in 2019, the Nepalese government issued 381 mountaineering permits for ordinary climbers. Each mountaineering permit can bring 11,000 to Nepal Dollar income. The New York Times pointed out that "the extra feet on the summit certificate are enough for some climbers to switch routes and choose to climb and spend money from Nepal."
Nepal is not without independent measurement of the height of Mount Everest. According to the Xinhua News Agency, in April 2019, a team of four Nepalese surveyors left Kathmandu to head to the southern slope of Everest Base Camp and began to independently measure the height of Mount Everest. To date, Nepal has not yet released new data.
Unlike Nepal, since 2005, China has chosen to use the rock face height as a measurement point. "The error in measuring the height of the snow surface is too large, and it changes too much throughout the year. As soon as the wind blows off the snow and the sun freezes, the height will decrease. The measurement time will be different, and the measurement results will definitely not be the same. And it is difficult to say who is right and who is wrong. The height of the rock surface only changes by 4 mm per year. If the interval between two measurements of elevation is 5 years, the difference in elevation is at most 2 cm. If the difference is too much, it means that there must be a wrong measurement. " Yamin explained to China News Weekly.
The height measurement of Mount Everest this time is also related to the Sino-Nigerian cooperation. During the state visit to Nepal from October 12th to 13th, 2019, the General Secretary of the CPC Central Committee and President Xi Jinping, the two countries issued a "Joint Statement", which stated that the two sides will jointly announce the elevation of Mount Everest and carry out scientific research cooperation. In order to implement the "Joint Statement", the Ministry of Natural Resources, together with the Ministry of Foreign Affairs, the State Sports General Administration and the Tibet Autonomous Region Government, organized the 2020 Mount Everest elevation survey.
Why must we climb to the top to measure?
The roads leading to the summit of Mount Everest are surrounded by dangers, and the organizers invested huge manpower, material and financial resources, and finally completed the measurement by measuring the climbers to the top. Why can't the well-known technologies such as satellite remote sensing images or GPS positioning systems directly measure Mount Everest?
Dang Yamin explained that satellite remote sensing images are mainly used for surface detection. At present, the accuracy in the elevation direction is about 2 meters, and the measurement accuracy is quite different from the centimeter level of geodetic technology. In addition, satellite remote sensing images can only measure the snow surface height. If no one reaches the peak to measure the snow depth, there will be no more accurate results.
Aircraft measurements are also not feasible. If you take the helicopter directly to the top, the operation of the Everest peak of more than 8,000 meters requires the aircraft to be extremely high. The peak is small, the helicopter cannot land, and the measurement personnel and equipment are put down in motion. The wind caused by the helicopter propeller may cause an avalanche. In addition, experts pointed out that the airflow at the summit of Mount Everest is unstable, how strong the wind, and the temperature is low, and the measuring drone cannot fly on the peak, nor has the experience of working on the peak of the robot.
China has twice announced the elevation of Mount Everest. At that time, there were two main methods of height measurement: the first is the traditional classic measurement method, based on the triangulation elevation method, combined with leveling, triangulation, wire measurement and other methods, the data obtained are corrected for gravity, atmosphere and other aspects. , And finally get the effective data of the height of Mount Everest. The second is the GPS satellite geodetic method used for the first time in 2005. First, a reference ellipsoid that best fits the shape of the earth must be established, and the accuracy of Mount Everest relative to this earth reference ellipsoid can be obtained by satellite GPS instrument Three-dimensional coordinates. As long as the elevation difference between the reference ellipsoid and the real earth at the highest point of Mount Everest is determined, the accurate elevation of Mount Everest can be obtained. The premise of GPS measurement is that someone puts the GPS receiver on the top of the peak.
The 2020 Mount Everest elevation survey, officially announced, will comprehensively use GNSS (Global Navigation Satellite System) satellite surveys, precision leveling, photoelectric ranging, snow depth radar surveys, gravity surveys, astronomical surveys, satellite remote sensing, and geoid precision A variety of traditional and modern surveying and mapping technologies.
The localization of the equipment is one of the highlights of the height measurement of Mount Everest in China. "Except for aviation gravity measurement, the rest is still using the 2005 technology, but this time a lot of domestic equipment was used." Dang Yamin told China News Weekly.
The global navigation satellite system satellite measurement is not a separate system, but consists of four systems: Beidou (China), GPS (United States), GLONASS (Russia), and Galileo (EU). "In 2005, GNSS satellite measurement mainly relied on GPS. This year, we will refer to the four global navigation satellite systems at the same time, and will mainly use the data of Beidou." Li Guopeng, the captain of the national test team, made the first news of the 2020 Everest elevation survey Introduction at the press conference. This is also the first application of Beidou system in the elevation measurement project of Mount Everest.
The first use of aviation gravity measurement technology is another new change. "This is a major advancement. Carrying out gravity measurement on Mount Everest, according to our previous calculations, the accuracy of the calculation can be improved by about 30% to 40%." Dang Yamin introduced.
"The height of Mount Everest that we see with our eyes is not its true height." Zhang Yanping, the commander of the Everest survey operation in 2005, mentioned in an interview at the time, "Because the earth is elliptical, the starting point of your sight is The point under your feet, not the point under Mount Everest, so you see Mount Everest lower than its true height. "Therefore, to accurately determine the height of Mount Everest, you must first find the altitude zero point at the foot of Mount Everest.
According to domestic regulations, the average sea surface of the Yellow Sea at Qingdao Tide Test Station in Shandong is used as the starting surface for calculating the altitude of the land. "Everyone can imagine a sea level, it is a curved surface, and all the gravity values on the surface are equal, this is the elevation surface. The surface where the Qingdao elevation zero point (level origin) is located has a gravity value, as long as the gravity is found under Mount Everest Value, you can find the starting surface. "Dang Yamin explained that aviation gravity measurement data can help us find out the starting surface of the elevation below the Mount Everest more accurately.
The advantages of aerial measurement are obvious, but the aircraft is too difficult to fly, and was rejected at first. Dang Yamin said that last year, when the Chinese Academy of Surveying and Mapping took the lead in formulating the Everest elevation measurement technology program, it consulted the flight companies and experts, and everyone gave a negative answer. Airborne gravity measurement is more suitable for measurement in low-altitude areas and plains. In the mountains, the normal flight height is below 9000 meters, and the highest flight can be up to 10,000 meters. However, it is very difficult and requires repeated technical demonstrations.
"The height of Mount Everest exceeds 8800 meters. It is very dangerous for the aircraft to fly at a height of 200 meters. The terrain on the north slope of Mount Everest in China is complex and the climate is unstable. Some people with flying experience judge that such a flight is very dangerous, even The plane will fall, this place cannot fly. "Dang Yamin introduced.
After the proposal was rejected, the Dang Yamin team was still not reconciled. By chance, they learned that the China Natural Resources Aviation Geophysical Prospecting and Remote Sensing Center could do it. It took half a year to collaborate to develop a detailed technical plan and invited two academicians to review it. Finally included in the plan for the height measurement of Mount Everest.
Unlike in the past, Li Guopeng mentioned in the mountaineering team's departure ceremony that a lot of preparatory work has ensured that the Everest elevation measurement task can be carried out as planned. This year, we will strive to achieve the first time that the mapping team and the mountaineering team will climb together.
If the mountaineering team is measured to reach the summit successfully, you still need to wait patiently if you want to know whether the height of Mount Everest has changed. According to Dang Yamin, after the data is measured, the final results can only be announced after 2 ~ 3 months.
"China News Weekly" No.17, 2020
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