The survey team then ascends with instruments, synchronizing measurements with climbing efforts, Chen said.

The surveyors need to carry fragile instruments as they ascend, making the task of climbing the mountain more arduous.

Sometimes, repeated trips are needed — like in 2020, when snowfall forced three attempts. Despite such setbacks, the repeated journeys often net better results, Chen said.

The professor noted, however, that without climbers fixing ropes, setting up camps and providing supplies, the task would be much harder.

During breaks in the weather, the team deploys a survey beacon to the summit and the Beidou system, Chen said.

The beacon, equipped with red prisms, allows six ground stations to measure distances via laser reflections, enabling triangulation. This ensures data collection continues even after the team descends, he said.

To ensure precision, multiple techniques — including global navigation satellite systems, leveling, photoelectric distance measurement, satellite remote sensing and gravity surveys — are combined. Rigorous calculations and verification yield the final elevation — 8,848.86 meters as of data released in 2020.