Ren Xiubo (right) displays a flag signed by his teammates during the geodetic measurement of Mount Qomolangma in 2005 at an altitude of 7,790 meters. CHINA DAILY

At 7,500 meters on the slopes of Mount Qomolangma, Ren Xiubo made a choice that would define his 27-year career: he removed his thermal gloves. Ignoring a direct order to descend during a sweeping blizzard, the then-25-year-old surveyor worked bare-handed for 10 minutes in sub-zero winds to secure a critical gravity measurement. It is a moment of "instinctive" duty that underscores the extreme physical lengths China's surveying teams go to in order to provide the foundation for the nation's economic and ecological maps.

For Ren, a member of the First Geodetic Surveying Brigade of the Ministry of Natural Resources, surveying Mount Qomolangma, also known as Mount Everest and the world's highest peak, was the rarest of opportunities.

"I did not know whether I would ever have the chance to reach that height again," Ren said. "At that moment, I had only one thought: I had to get the data."

By the time the measurement was completed, his hands had lost all feeling. During the descent, he repeatedly struck them against an ice axe to stimulate the nerves. Only after several hours did sensation slowly return.

That day, Ren and his teammates pushed China's gravity measurement and satellite positioning work on Qomolangma to 7,790 meters, a record at the time.

Now a senior engineer, Ren does not describe the decision as heroic. To him, it was simply what the mission required.

"It was instinct, a natural reaction," he said. "It is also the kind of commitment rooted in the bones of our surveying team."

Born in 1979 in Yulin, Shaanxi province, Ren has spent much of his 27-year career in mountains, deserts, plateaus and remote areas. He has taken part in China's two Qomolangma elevation measurement missions, in 2005 and 2020, and more than 30 major national projects, including the national highway network, post-Wenchuan earthquake reconstruction and the West-East Gas Pipeline project.

His brigade has long been at the forefront of China's surveying work.

In 2015, President Xi Jinping sent a letter to its veteran Party members and former members, encouraging them to remain true to their mission and continue measuring the country's mountains and rivers with precision.

"What supports us in harsh field conditions is the original mission of surveying for the country," Ren said. "It is also the surveying spirit of loving the motherland and the profession, working hard and making selfless contributions."

To many people, surveying may seem far removed from daily life. Ren sees it differently.

"If national economic development is like constructing a building, surveying is the foundation and framework," he said.

Maps, navigation, location services, intelligent driving, food delivery, ride-hailing and express logistics all rely on basic surveying data. Such data also supports natural resource management, territorial spatial planning, major engineering projects, disaster relief and ecological protection.

"Surveying is a foundational undertaking for economic development, national defense and social progress," Ren said.

In 2005, Ren was still a young team member. He said he was "following the older generation", obeying commands, overcoming altitude sickness and completing his assigned tasks.

During that mission, he worked for more than 40 consecutive days in areas above 6,500 meters. At the 6,500-meter camp, strong ultraviolet rays darkened and cracked his face, while fierce winds cut into his skin day after day. At the 7,028-meter camp, on the eve of a summit measurement attempt, he solemnly wrote his application to join the Communist Party of China.

"I had prepared for everything, including the worst," he said. "Even if I had to leave my life on Qomolangma, I had to complete the surveying mission."

The members of the 2020 Mount Qomolangma measurement team take a group photo after the descent to base camp at 5,200 meters at the end of the successful mission on May 28, 2020. JIGME DORJI/XINHUA

On May 22, 2005, the mountaineering survey team successfully reached the summit and completed the measurement mission. China later announced the rock-surface elevation of Qomolangma as 8,844.43 meters.

Ren did not reach the summit that year. Some later asked whether he felt regret.

"Perhaps there was regret," he said. "But surveying is our job, and completing the mission always comes first."

Fifteen years later, in 2020, Ren returned to Qomolangma. This time, he took on coordination, publicity and support work for the summit measurement mission, while passing on practical experience to younger colleagues.

Before the mission, Ren repeatedly reviewed possible emergencies, from equipment operation and resistance to extreme cold to contingency plans for bad weather after the summit team reached the peak.

"We had to anticipate every difficulty we could think of," he said. "Only then could we do our best to ensure the mission was foolproof."

The 2020 mission proved far more difficult than expected. The first summit attempt was halted near the North Col ice wall above 7,000 meters because of deep snow, strong winds and avalanche risks. A second attempt was forced back by a storm, leaving less than a week of suitable climbing time.

Ren said the team encouraged one another and kept refining the plan. On May 27, the summit team successfully reached the peak and completed the measurement. Coincidentally, the date was also the day China's older generation of surveyors had reached the summit in 1975.

But reaching the summit was only the first step. The summit marker had to be set up three times before the Beidou navigation satellite system receiver began working properly. The snow-depth radar also had signal problems, which the team members solved on site.

Only after two and a half hours of summit operations, and another 36 hours of waiting to confirm the data was valid, did Ren and his teammates feel relieved.

Beyond Qomolangma, Ren has also witnessed the growing role of surveying in emergency response and ecological protection.

In 2015, after a major landslide struck Shanyang county in Shaanxi, members of his brigade stayed in the core danger zone despite the risk of secondary landslides. Their monitoring data helped protect rescuers and provided support for scientific disaster relief.

The same year, the brigade set up an emergency surveying center focusing on drones, aerial remote sensing, image processing and 3D modeling. Ren helped build the team, train operators, produce orthophoto maps and formulate emergency response plans.

Ren said modern surveying must keep pace with new technologies such as Beidou navigation, satellite remote sensing and real-scene 3D modeling.

Ren is committed to working on new basic surveying, the construction of a real-scene 3D China and the building of spatiotemporal information databases, providing accurate support for natural resource monitoring, ecological change detection and territorial spatial planning.

"I will continue to visit schools, enterprises, institutions and communities," he said. "I want to share the stories of surveying for the country and plant the seed of responsibility for protecting nature."

yangzekun@chinadaily.com.cn