Measuring Mt Everest: because it is there

The Nepal Mt Everest Height Measurement Expedition Team climbed the world’s highest mountains last year to determine its exact altitude. 

Although the height Mt Everest has been accepted as 8,848m (29,028ft) since 1955, later measurements have been higher or lower than that. Previous calculations were by Americans or Europeans, and Nepal and China needed to make their own measurement of the peak on their border. 

In 1856, the Great Trigonometric Survey of India found Mt Everest’s height to be 29,000ft, and the highest mountain in the world. But the British surveyors through the all the zeroes would give people the impression that the elevation was rounded off. So they added 2ft to make it a more exact-sounding 29,0002ft.

The true elevation of Sagarmatha is not constant because of tectonic activity, and there was a need to update it after the 2015 earthquake. The Survey Department installed GPS equipment on the summit, and uses geodesy, levelling and gravity measurements and is processing the data. 

A very accurate sea level height for Sagarmatha can now be expected, since the Survey Department used state-of-the-art equipment at the summit, and had  other survey data. It will also help Nepal now to use this GPS technique to more accurate measure the heights of Nepal’s other mountains. 

The Survey Department has used historical trigonometry levelling as done by Survey of India in the 1950s, and combined it with more exact levelling and modern geoid systems with gravity survey, and Global Navigation Satellite System (GNSS) to cross check results. 

The Survey Department selected 12 trigonometry observation points in Solukhumbu, Khotang, Bhojpur and Dolakha districts from where we measured the position and angle of the summit. We plotted the elevation of points from sea level right up to the base of Mt Everest. 

For its part, the ground penetrating radar (GPR) on the summit measured the thickness of the ice cap above the rock at the summit, so that we can know the rock height of the summit. 

After 26 days at Base Camp, preparing, planning and acclimatising for the final push for the summit, our team headed up the Icefall 18 May, 2019. 

Our goal was to reach the top to conduct the measurements, but even more importantly, our mission was to return back down safe and sound. Our team had to take survey instruments and then conduct observations to pinpoint accurately the elevation of the highest point on earth.  

The observations we were conducting would be one of the most critical information in determining the height of Sagarmatha. Precise and meticulous calculations based on the measurement we would make at the top along with survey observations by several other teams would result in the definitive height of Mt Everest. 

While we conducted Global Navigation Satellite System (GNSS) observation at the top, these measurements would have to be linked to similar data from base stations. This was managed by a different survey team located in Lukla. 

Our expedition included four surveyors from the Survey Department and four Sherpa colleagues.  Me and surveyor Rabin Karki were to head for the summit with our guides, while surveyors Yubaraj Dhital and Surveyor Suraj Singh Bhandari would stay at base camp and coordinate with other teams. 

Our guides included Tshiring Janbu Sherpa, Lakpa Sherpa, Dorji Sherpa and Pem Ngima Sherpa. Tshiring and Ngima had already summited Everest twice each, while for other Sherpas it was their first time. It was the first time for Rabin Karki too.  This was my second summit bid, after having got to the top in 2011 with the Civil Servants’ Expedition. 

From Base Camp, we reached Camp II the same day and stayed there overnight and headed on to Camp III at the base of the Lhotse Face, which we reached at 3pm on 19th May. 

The next day, we climbed the steep icy flanks to reach Camp IV at the South Col by mid-afternoon. It sounds easy to say, but this was technical climbing at high altitude, with hurricane force winds at the South-Col. But that was the least of our worries: we found out when we got to camp that the stockpile of oxygen that was supposed to be at Camp IV had not yet arrived. 

Usually, all expeditions carry oxygen bottles to the South-Col within the first week of May, and store it there for the summit teams that come later. We had received information that our cylinders would also be stored at the South Col in time for the summit day. 

However, we found that not all the cylinders had actually reached the South Col, and understandably our head guide Tshiring indicated that we could not attempt the summit without them. He felt it would be better to descend to Camp II and climb again when enough oxygen bottles reached the South-Col.

This was a difficult moment. At that altitude, with our decision-making already somewhat impaired by lack of oxygen, we hesitated. Descending 3,500m to Camp II and climbing back up was not going to be a walk in the park.

In addition, the weather window for the summit push was narrow, and then there could be a heavy traffic of climbers on the southeast ridge. This was going to be a make-or-break decision. Going back down to Camp II would, for all intents and purposes, mean failure of the mission – we might as well just descend all the way back to Base Camp and go home. But without the necessary oxygen, we would be risking our lives on the summit bid. 

As the leader of the expedition, the decision was on my shoulders. It was not an easy one, since the lives of my colleagues depended on it. But just the thought of giving up the expedition was too devastating to even think about. 

So, as team leader I decided that we go ahead. Failure was not an option. I remember telling Tshiring, “I simply cannot give up this historical mission when we are so near the top.”

When there is a will, as they say, there is a way. I persuaded the team to stay overnight at Camp IV, and then went around the other expeditions at the South Col from Seven Summit and Pioneer to loan us oxygen cylinders. Fortunately, our Sherpa colleagues found a stash at the Geneva Spur at 7,600m. 

Experience from my previous expedition was helpful in making my decision, since I was aware of my own limitation and capability. I had also made a lot of friends among the guides during my 2011 expedition, and they had helped me out of some tricky situations. This was useful in breaking the ice, as it were. 

By the morning of 21 May, with the help of our Sherpa friends at the South Col, we had managed to collect enough bottles for the push. We decided to head off for the summit at 2PM, which was unusual because most climbers start from the saddle at about midnight and take 10-15 hours to reach the top. 

There was some disagreement about this from our guides, who said it was not a good idea because it would mean that we would be on the summit at night when it would be too cold to install our equipment and take measurements. “If it is too cold, we cannot even take off our mittens to work with the equipment,” one of them said. 

But, from my experience from eight years previously, I had my reasons for starting out so early (or so late in the day). The foremost reason was that we did not want our survey activities and measurements to be disturbed by the rush of climbers on the summit. 

Secondly, satellite positioning data is much more accurate if it is made at night instead of at sunrise. The ionosphere effect is minimal if the GNSS observation is carried out at night because it depends on signals coming from satellites to the receiver.

At least that was my theoretical conclusion after reviewing relevant literature regarding observation time for achieving high quality GNSS data. This expedition was all about accuracy, and we had to do everything in our power to ensure that there would be no margin for error in our measurements. 

We made progress up the ridge, and by 9:30pm had reached the Balcony at 8,450m. I remember being very thirsty, and took out two flasks that I had filled with hot water at the South Col. One of the thermos flasks had been provided by the Nepal Mountain Academy at a training four months previously, and another was given to us by Peak Promotion. 

To my dismay, I found that the water in both flasks had turned to ice. Dehydration can be a serious issue at this altitude, but there was no choice. There was also no sense in carrying that extra weight, so I left the bottles at the Balcony where we rested for a bit under the starlight.

It took us another three hours to reach the South Summit at 1:30am, where we rested briefly and pressed on. Another hour-and-half, and we were at the summit. At 3:00am on 22 May I was on the top of Mt Everest for the second time. Unlike the previous climb, however, it was pitch dark, very windy, and I was utterly exhausted after 13 straight hours of trudging up the mountain. I had nothing left in me physically, and just thinking about the descent made me nervous.

But there was no time to think about anything, there was work to be done. We were here on a mission to find out the exact altitude of the spot we were standing on.  Despite the extreme tiredness, howling wind, the numbing cold, we had to complete our GNSS survey and the Ground Penetrating Radar (GPR) observation in the limited time window at our disposal. We were completely focussed on our work, which we had rehearsed many times at base camp.

Our team, made up of the very strong and capable survey officer Rabin Karki, the excellent mountain guide Tshiring Jangbu Sherpa and other climbing colleagues, was able to capture the crucial bits of data that would help us solve the riddle of the exact height of the Mount Everest. 

We stayed on the summit for almost two hours installing the GNSS equipment on a small and sturdy tripod designed especially to work on the summit of Mt Everest. Unlike the tripod provided by the manufacturer, this one was light-weight and stubby, allowing greater stability in the high wind. It also had a special type of locally-designed steel screw about 30cm long to fix it to the ice on the summit. I had a hand in designing this contraption from my previous experience of seeing the character of the terrain and the topography of the summit. 

The tripod should have also been able to withstand the high winds blowing over the summit all the time. The direction of the wind, although it is predominantly westerly, can also change to the south or north. In order to stabilise the tripod while the wind was blowing, some of us got down on the snow and held the tripod’s legs firmly. The idea was to ensure that the tripod was stable and there would not even the slight displacement that could throw the data off. 

Stuck at the Hillary step 

By about 4am, as the eastern sky started lighting up, other climbers began to arrive at the summit. This was why we came up early, so that the crowds would not disturb the sensitive instruments. I was now worried that the climbers would affect the sensitive data we were collecting. However, members of our team kept the climbers from going near the GNSS antenna at the top. 

When I realised that we had collected all the data that was required, we packed our bags and started to head down. I put the main height measuring GNSS antenna in my bag, while Tshiring carried the other gear.

Although it was daylight, the descent was a challenge. Our progress down was delayed by the throng of climbers heading up towards the summit. From the top to the South Summit, we had to wait to let climbers pass who unclipped and clipped again to the single rope on the ridge. At the Hillary Step, we have to wait two hours just to wait for our turn on the one-way route. 

We had our equipment with all the precious data that we had so painstakingly collected at the summit in our bag. The data does not weigh anything, but it weighed us down with responsibility to protect it during this treacherous descent. 

In fact, I later found out that 22 May, 2019 had the highest number of climbers on the summit, and news about the ‘traffic jam’ on Mt Everest had gone viral around the world. A total 223 mountaineers summited on that day, and there were calls for restricting numbers. As luck would have it, not a single expedition has put climbers on the summit from the Nepal side of Sagarmatha in 2020 because of the Covid-19 restrictions.

Last spring, there was a very short weather window for summit planning. According to weather reports, less wind and good weather was forecast for 22 May compared to the days before and after. That is why there were so many climbers on the summit all at the same time. 

While we were descending from the South Summit which is at about 8,600m Rabin Karki’s oxygen system started giving him trouble. This was dangerous, and his life was at risk. Our guide Tshiring Jangbu Sherpa borrowed an extra oxygen cylinder from another Sherpa colleague, and Rabin managed to continue his descent. 

I myself was drained, and did not have much energy left by the time we got back down to the Balcony. My condition got worse, and on the slope down to the South Col at one point I actually lost consciousness at 8,200m. I must have lain there for two hours in the blue ice, until another climber kicked me to see if I was alive. 

After I woke up, I found that the rest of the team had headed on down thinking that the South Col was close, and I would catch up with them. Tshiring must have thought that I could descend by myself. Those two hours gave me frostbite, and when I got back to Kathmandu I had to amputate a tip of my left toe. 

Normally, if climbers fall unconscious at that altitude, and there is no one to  help them down, it is likely that they will not wake up again. It was that kick, and a miracle, that woke me up so that I could stumble down the mountain that day, and bring down the precious cargo of data in my backpack.

This near-death experience reminded me of the importance of the summit observation and the responsibility that I had in bringing down the data. We took risk not only for the sake of successful completion of the historical mission, but also for the qualitative raw data so we could get the precise height of Mt Everest. 

Khim Lal Gautam is the Chief Survey Officer at the Survey Department, Ministry of Land Management, Cooperatives and Poverty Alleviation, Government of Nepal.