Who Measures the Height of Mount Everest and How?

Nepal has spent US $1.3 million on the project, working with six global firms since 2017.
October 19, 2020, 2:00pm
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Nepal was supposed to announce the new height of Everest on May 29, 2020, but the announcement has been pushed back amid the COVID-19 pandemic. Photo courtesy of Jewel Samad/AFP. 

Khim Lal Gautam and Rabin Karki from the Survey Department of Nepal, and Tshiring Jangbu Sherpa, their guide, reached the top of Mt. Everest on 22 May, 2019. The three person team was carrying over 40 kilograms of equipment, including a GNSS receiver and a snow depth ground penetrating radar. They had left Kathmandu on 11 April, and over a month into the trek, in the bitter cold, Gautam, the lead surveyor, had lost a toe to frostbite. The surveyors made it to 8000 meters on the mountain when, on 21 May, they were stuck in a “traffic jam” of climbers trying to make it to the summit. When they reached the top a day later, data from the GNSS receiver was collected for an hour and 16 minutes in minus 109 Fahrenheit, after which the surveyors began their descent, concluding the most difficult phase of Nepal’s first official mission to measure the height of the tallest mountain in the world.

Mount Everest’s current accepted height, 8848 meters, is a figure that was obtained by the Survey of India in 1955. Since then, other Indian, American, European, and Chinese surveyors have remeasured the mountain, and produced figures ranging between 8844 meters and 8850 meters. Due to the cost and technical expertise required for the project, Nepal government had not launched its own measurement effort till 2017.

“The earthquake in 2015 caused changes in the positions of the mountains,” former deputy director general of the Survey Department, Niraj Manandhar told VICE News. “Remeasuring was extremely difficult, but had to be done in the aftermath of the earthquake.”

India Nepal Everest Survey

The team of surveyors from Nepal's Department of Survey on their way to the summit. Photo courtesy of Nepal Department of Survey.

Dr. Christopher Pearson from the School of Surveying at the University of Otago, New Zealand, an advisor to Nepal’s Survey Department, told VICE News that there are three reasons why the remeasurement of the mountain was necessary. One, tectonic activities are such that the height of Mt. Everest is expected to increase between earthquakes and decrease in the aftermath of an earthquake, which means that there may have been a notable change after the shocks of 2015. Two, with improvements in satellite technology, the precision of measurements has gotten markedly better, meaning that new figures on the height of the mountain are likely to be extremely accurate. Three, the top of Everest is covered in ice, and the melting of ice also means that the height may have fluctuated.

In addition to the project’s scientific relevance, measuring Mount Everest has also been a matter of national pride for the Nepal government. The Survey Department has spent US $ 1.3 million on the endeavour, working alongside six international firms since 2017.

“We are using traditional methods as well as cutting edge modern techniques for the first time, it is a very important project for Nepal,” the current Deputy Director General of the Survey Department, Susheel Dongol, told VICE News.

The traditional and modern methods for measuring Mount Everest are the trigonometric method and the satellite method respectively. The trigonometric method, through which the height of the mountain was first determined in 1955, measures the angle from horizontal points away from the mountain in order to make calculations on the height. The satellite method requires surveyors to place a satellite device on top of a mountain, which determines the peak’s exact location in a given coordinate system, and a series of calculations from the data thus obtained determine height with a margin of error of a few centimeters.

According to Dr Pearson, a problem with the trigonometric method is that light rays bent by the atmosphere can make a mountain look bigger or smaller, while the challenge with the satellite method is that it measures an ellipsoidal height (the height above a smoothed geometric model of the earth)instead of the height over sea level. Both methods used concurrently, therefore, lead to the most accurate figure.

The Survey Department measured the position and angle of the summit from 12 observation points for trigonometric levelling. A gravimeter— an instrument which measures the force of gravity at any given location— was taken to 298 spots. The ground penetrating radar measured the thickness of the ice-cap at the top of the mountain. The massive data collection effort included over 80 staff members from the Survey Department and took place over two years between 2018-2019 with geodetic equipment contributed by various countries. Most of the analysis of the data was conducted in late 2019.

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Surveyors conducting precise levelling. Photo courtesy of Nepal Department of Survey

If it wasn’t for the pandemic, the new height of Everest may already have been made public, but COVID-19 and tensions with China have delayed the announcement of the height. The “ownership” of the mountain, which lies on the border between the two countries, has long been a point of contention,  and although the relationship between Nepal and China has been quickly advancing in recent years, state communication about matters relating to the mountain is a diplomatic tightrope. In October 2019, after Chinese President Xi Jinping’s state visit to Kathmandu, a statement by the Nepali and Chinese government said that they would “jointly announce the height of Mount Sagarmatha/Zhumulangma” (Everest). A year after Gautam and Karki reached the top of the mountain, on May 28, members of the Chinese government’s survey team also reached the summit to collect data. Although the measurement efforts have been separate, the promise of a joint announcement means that Nepal’s “pride project” is no longer its own.

A senior member of the Survey Department who did not want to be named said that China’s involvement was a “blindside,” and there is “no clarity” about when the public announcement of the new height will take place.

This is not the first time that the height of Everest has been a source of tension between Nepal and China. In May 2005, when Chinese researchers concluded that the height of the peak was 3.7 meters less than the estimates made in 1955 (they excluded the height of the ice cap at the top of the mountain in their calculation), then Director General of the Survey Department, Raja Ram Chhatkuli had said, “Both are correct heights. No measurement is absolute. This is a problem of scientific research.”

In 2010, the countries agreed to settle their differences, with the Chinese side accepting Nepal’s claim that the snow height of Mount Everest is 8,848 meters, and the Nepali side recognised the Chinese claim that the rock height of the mountain is 8,844.43 meters.

The joint announcement decision appears to have taken place without the Survey Department’s knowledge. In October 2019, the Survey Department told The Kathmandu Post that ten days after the public announcement, it had not received official communication from the Prime Minister’s Office regarding China’s involvement in the process, suggesting that those involved with the science of the measurement and those in charge of state messaging were not on the same page.

A year after the announcement that the height of the mountain would be jointly announced by Nepal and China, the Survey Department has been circumspect on the timeline of the declaration. “It was a long and difficult process, and the reveal will come in due time,” Damodhar Dhakal, information officer of the Survey Department told VICE News.

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