When the world gets closer.

We help you see farther.

Sign up to our expressly international daily newsletter.


Measuring Mount Everest -- With Ever More Precision

Mount Everest is unquestionably the world’s highest mountain – but just how high, exactly, is it? Toting the latest technology, a team of climbers is heading for the rooftop of the world to find out.

Everest and the Rongbuk Monastery in Nepal
Everest and the Rongbuk Monastery in Nepal
Thomas Jüngling

There is no reliable fixed point anywhere on earth. Everything is in flux. The sea moves back and forth in a regular ebb and flow. The moon's gravitational pull also influences the earth's crust, which rises and falls daily by as much as 60 centimeters. Even the North and the South Pole move a couple of centimeters every year.

Despite this, technicians working for the Nepalese government have been charged with determining the exact height -- to within a few centimeters -- of Mount Everest. Helping them are mountain climbers and some very high-tech equipment.

Using very simple means, James Nicolson was the first to measure the altitude of the world's highest mountain 150 years ago. He recorded 8,840 meters – just over 29,000 feet. That was astonishingly close to the present widely-accepted figure, which is 8,848.40 meters, but which is, however, disputed by some. The technicians presently measuring Everest are due to present their results to the Nepalese government in two years' time.

Their most important tool is the Global Positioning System (GPS), which involves two dozen satellites that orbit the Earth and send radio signals. The satellites are placed in such a way that four of them cover every part of the planet at any given time. Since their exact positions are known, GPS receivers like the Leica Geosystems SmartRover can calculate their own positions from the data and exact time.

Since these receivers only weigh a few kilograms, they can be brought up to Everest's peaks with relative ease. Measurements are made every two seconds for about an hour. As the GPS signals are not disturbed on their way through the ionosphere and the troposphere, measurement technicians can combine the data measured on the mountain with data from the GPS receivers on the ground.

Beams and prisms

Also in use are tachymeters that measure both horizontal and vertical angles as well as distance, and beam infrared rays that reflect off prisms placed on the mountain peaks. Distance can be measured by the amount of time it takes the beam to reach the prism and return.

Another tool used by the technicians are planes equipped with an airborne scanner that scans the mountain. Some have a sensor that takes pictures of the mountain, operating like a camera – but with a lot higher resolution. Points on the pictures can only be exactly defined if the flying altitude at the time the picture was taken can be precisely determined.

The geodatists have to take numerous influences and conditions into account, starting with base level -- the usual reference point being sea level. This can, however, vary. For example, around Sri Lanka the Indian Ocean level measures 105 meters lower; to the northeast of Australia, it's nearly 80 meters higher, which is why technicians calculate an average theoretical sea level for every point on earth.

The earth's gravitational field isn‘t the same everywhere either, and that also has to be taken into account in the measurements. This is not a reading taken on the mountain. "To do that, you'd have to use a gravimeter and they are very heavy. The National Geographic Institute (IGN) in Paris tried twice to get one up a mountain and failed both times," says Farouk Kadded, a product manager at Leica Geosystems who also leads expeditions on France's Mont Blanc.

When used in the mountains, GPS receivers, tachymeters and sensors are extremely sensitive to weather conditions. Temperatures on Mount Everest are around minus 40 degrees Celsius, and atmospheric pressure around 326 millibars – about a third of normal pressure on the ground. This too has to be taken into account in calculating measurements.

There are myriad of other areas that could lead to miscalculation. For example, how high the snow cover is on the mountain has to be subtracted from the result: the point is to calculate the elevation of the naked rock. If a geodatist on the mountain were to jam his GPS device mounted on a pole seven centimeters into the snow, measurement results would be false. Radars and spectrometers can measure the thickness of snow by emitting waves of different lengths.

In view of all this high tech effort, the question poses itself: What for? For one thing, spectacular projects of this type enable the manufacturers of various devices to get a lot of publicity, says Kadded. But also "because we can test the reliability of our Leica Geosystems GPS devices."

"On Mont Blanc, every two years we measure not only the height at the top but a lot of other points to determine the form and volume of the ice cap and to be able to trace the changes over time," says Kadded.

Such data is crucial, he says, to climate researchers, meteorologists, glaciologists -- and nivologists: scientists who study snow.

Read the original article in German

Photo - Steve Hicks

You've reached your limit of free articles.

To read the full story, start your free trial today.

Get unlimited access. Cancel anytime.

Exclusive coverage from the world's top sources, in English for the first time.

Insights from the widest range of perspectives, languages and countries.

FOCUS: Russia-Ukraine War

That Man In Mariupol: Is Putin Using A Body Double To Avoid Public Appearances?

Putin really is meeting with Xi in Moscow — we know that. But there are credible experts saying that the person who showed up in Mariupol the day before was someone else — the latest report that the Russian president uses a doppelganger for meetings and appearances.

screen grab of Putin in a dark down jacket

During the visit to Mariupol, the Presidential office only released screen grabs of a video

Russian President Press Office/TASS via ZUMA
Anna Akage

Have no doubt, the Vladimir Putin we’re seeing alongside Xi Jinping this week is the real Vladimir Putin. But it’s a question that is being asked after a range of credible experts have accused the Russian president of sending a body double for a high-profile visit this past weekend in the occupied Ukrainian city of Mariupol.

Stay up-to-date with the latest on the Russia-Ukraine war, with our exclusive international coverage.

Sign up to our free daily newsletter.

Reports and conspiracy theories have circulated in the past about the Russian leader using a stand-in because of health or security issues. But the reaction to the Kremlin leader's trip to Mariupol is the first time that multiple credible sources — including those who’ve spent time with him in the past — have cast doubt on the identity of the man who showed up in the southeastern Ukrainian city that Russia took over last spring after a months-long siege.

Russian opposition politician Gennady Gudkov is among those who confidently claim that a Putin look-alike, or rather one of his look-alikes, was in the Ukrainian city.

"Now that there is a war going on, I don't rule out the possibility that someone strongly resembling or disguised as Putin is playing his role," Gudkov said.

Keep reading...Show less

You've reached your limit of free articles.

To read the full story, start your free trial today.

Get unlimited access. Cancel anytime.

Exclusive coverage from the world's top sources, in English for the first time.

Insights from the widest range of perspectives, languages and countries.

The latest