The search for accuracy on the roof of the world

China had conducted six previous surveys.

1. 1966 and 1968

The State Bureau of Surveying and Mapping and the Chinese Academy of Sciences sent two teams of surveyors to measure the mountain. However, due to a lack of experience and practice, plus the limitations of technologic support, the results were never officially revealed.

2. 1975

The third official attempt to measure the mountain was undertaken by 49 participants from the China Mountaineering Team and the State Bureau of Surveying and Mapping.

At 2:30 pm on May 27, nine mountaineers carried a surveyor's beacon, which played a crucial role in traditional height measurement, to the summit.

In addition to the height of the mountain, they measured the depth of snow on the summit. On July 23, the government announced Qomolangma's height as 8,848.13 meters (excluding the layer of snow covering the summit).

3. 1992

Surveyors conducted the fourth large-scale measurement of the mountain with the help of a team of Italian mountaineers. Multiple surveys were conducted, not only at the summit, but also at the North Base Camp. GPS was used for the first time to measure the world's highest mountain.

4. 1998

Cooperating with mountaineers from the United States, surveyors from the 1st Geodetic Surveying Brigade measured Qomolangma for the fifth time. However, a surveyor's beacon could not be placed on the peak as the summit attempt was unsuccessful.

5. 2005

On May 22, Chinese mountaineers reached the summit and made several measurements. During the following five months, the country's top experts in mapping, geography and math conducted a series of calculations on the data collected, with 20 academicians involved.

On Oct 19, the State Bureau of Surveying and Mapping officially announced the new height of Qomolangma as 8,844.43 meters. The previous height, 8,848.13 meters, was no longer used.

Experts explained that the difference between the numbers released in 1975 and 2005 mainly resulted from improvements in technology.

The measurement in 1975 included the snow covering the summit, while a layer of ice between the snow and the rock was not detected, leading to an inaccurate measurement. The figure calculated in 2005 was far more precise, experts said.

Source: Ministry of Natural Resources