How Was Mount Everest Measured? And by Whom?

Everest is the highest mountain in the world. But it isn’t next to the sea, so how was the measurement of 29,031 feet (8,848m) above sea level arrived at? And who first measured Mount Everest, and why?

Mount Everest was measured using imaginary triangles and basic mathematics. Everest was measured by British surveyors, who figured out how high it was in 1854.

The story of the Great Trigonometrical Survey started with tigers, camels, lost villages, elephants, goats, telescopes and surveying instruments. It ended with the discovery of the highest point on the earth’s surface.

When the British got round to surveying the Himalayas they finally discovered Everest. It was a huge mountain hiding at the back that, when measured, proved to be higher than any other mountain in the world.

But how did they know it was the highest mountain? You could hardly dangle a ruler down the side of Everest. So how was it done?

Mount Everest was measured with imaginary triangles and telescopes
Mount Everest was measured with imaginary triangles, and telescopes

The British in India decided to survey the land they had colonised, so they commissioned a Great Trigonometrical Survey in 1802. Imaginary triangles were to be drawn all over India, starting at the southern end and eventually reaching the Himalayas over 1,500 miles away.

The measurements made by the surveyors had to be very accurate otherwise errors would build up by the time they reached the Himalayas.

A baseline between two points visible to each other about seven miles apart would be carefully measured with 100ft chains. If there was a village in the way it would be moved, and 50ft stone towers were built at the end of the baseline if there wasn’t a hill available.

Two Bhutanese women standing next to a tent.
Hundreds of local people living in camps accompanied the Great Trigonometrical Survey. These womens’ hats were not surveying instruments.

Then a huge brass theodolite would be hoisted to the top of the tower. This was a precision optical instrument for measuring angles between visible points in the horizontal and vertical planes. With this, the exact angle between the baseline and the sightline to a third point would be measured.

Sightings were made using mirrors to flash sunshine at far-distant colleagues, and blue lights were used at night if the heat of the Indian day caused refraction.

A triangle was drawn on a map and as the length of the baseline and the two angles were known, the length of the other two sides could be worked out. This meant that surveyors didn’t have to measure them on the ground.

When they finally got to the Himalayas sixty years later the heights of the mountains were calculated by measuring their angle of elevation from several different places, drawing vertical imaginary triangles this time. This meant that the surveyors could now work out the height of distant unclimbed mountains in an inaccessible country.

A typical expedition employed four elephants for the surveyors and 30 horses for the military officers – both groups wanting to avoid tigers – and more than 40 camels for the equipment. The 700 accompanying labourers travelled on foot and had to take their chances with the tigers.

Mount Everest's North Face
They had found the highest point on the earth’s surface

Eventually this huge project reached the Indian border with Nepal, a country that was forbidden to the British. The surveyors focused their instruments on the far Himalayas, drew their triangles and measured 79 of the highest mountains, including K2 and Kangchenjunga.

Eventually they computed in 1854 that the highest of all was a mountain on the remote border between Nepal and Tibet. They had to allow for the gravitational pull of the Himalayan range (which will distort even the surface of a puddle), the refraction of the atmosphere and a number of other variables, and it is just amazing that they got the height so close: 29,002ft. (source: wikipedia)

Legend has it that the calculation was exactly 29,000 feet, but it was felt that no-one would believe it! So a couple of feet were added to make it more believable. It took over 150 years to get a more accurate result.

China now states that the measurement should be made up to the topmost rock, at 8,844m (29,015ft), whereas Nepal measures to the top of the overlying snow-cap, at 8,848m (29,028ft). The US National Geographic Society measurement using satellites came to 8,850m (29,035ft) – a difference of 33ft from the original Colonel Everest’s Great Trigonometrical Survey result, or around 0.1 per cent error.

Amazing, considering the pioneers were using telescopes and brass theodolites, aimed from across the border.

The first scrawl on the map describing Mount Everest called it ‘Peak B’, then it was ‘Peak XV’, like K2 in the Karakorum.

In the end, though, the British chose the name of the former Surveyor-General Sir George Everest. He never saw the mountain that bears his name, but Andrew Waugh, Everest’s successor as Surveyor-General in India, wrote:

‘… here is a mountain most probably the highest in the world without any local name that I can discover …’, so he proposed ‘to perpetuate the memory of that illustrious master of geographical research … Everest’. (source: surveyhistory)

This went against map-making practice, which was always to use local names, and it was the start of the long story of Mount Everest being hijacked for politics and glory.

Colonel Everest himself said his name could not be written in either Hindi or Persian, and nor could the local Indians or Nepalis pronounce it. Nor can we! He pronounced his name Eeev-rest, as in “Adam and Eve”, while the rest of us mispronounce it as Ever-rest, as in “ever and ever”.

By the way, to answer the question “Before Everest, What Was the Highest Mountain?”- find out here.

About Graham Hoyland

Graham was the 15th Briton to Climb Mount Everest. He has spent over two years across nine expeditions to the mountain and is the author of Last Hours on Everest, the story of Mallory and Irvine's fatal ascent.