"Nepal has ordered a new survey of Mount Everest to end the "confusion" over the exact height of the world's highest mountain, a government spokesman has said.
The official overall height of Everest is designated as 8,848m (29,029ft). But China and Nepal have had a long-running disagreement over the height.

The Chinese have argued it should be measured by its rock height. Nepal said it should be measured by its snow height - which is four metres higher. The world's highest mountain traverses the border of the two countries. Last year the two sides agreed that Mount Everest should be recognised as being 8,848m high. But Nepal government spokesman Gopal Giri told AFP news agency that, during border talks between the two countries, Chinese officials often use the rock height.
"We have begun the measurement to clear this confusion. Now we have the technology and the resources, we can measure ourselves," Mr Giri said. "This will be the first time the Nepal government has taken the mountain's height." He said stations will be set up at three different locations using the global positioning system, and the task of measuring the peak would take two years." http://www.bbc.co.uk/news/world-south-asia-14213137

"The world's tallest mountain was named after British surveyor George Everest in 1856, when a trigonometric survey put its height at 8,840 metres (29,002ft).
But when last measured in 2005 by China's state bureau of surveying and mapping, its rock height was calculated at 8,844.43m (29,017ft), plus a 3.55m ice cap. This was still 7cm less than the elevation determined by an Indian survey in 1955.
To complicate matters further, in 1999 an American expedition to Everest using GPS technology for the first time got a rockhead elevation of 8,850m, and an ice elevation 1m higher.
It does not help either that due to shifting tectonic plates, Everest grows by 4mm every year." http://www.guardian.co.uk/world/2011/jul/20/nepal-survey-mount-everest-height