# how was the height of mount everest found?

I know it was with trigonometric functions, but can anyone provide more details? pleasee

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Goerge Everest (pronounced eve-rest) was Surveyor General of India. India was survey in exacting detail by constructing towers and measuring the distance (with a fixed length surveyors chain) and angles (with a theodolite).

Using two towers in sight of the summit, the elevation can be determined. You know the elevation of the towers because your survey started at sea level. You know the distance between them. From each of them, you measure the angle to the summit relative to North. You can now work out the distance to the summit by angle-side-angle geometry. You also know how the angle relative to the ground by which you have to look up. to see the peak. This second triangle gives you the elevation (opposite leg) by setting the ratio with the distance to the summit (adjacent leg), by using the tangent.

Now all of this is done in spherical geometry, not plane geometry. It is also done in the real world where you have to compensate for atmospheric distortion, thermal expansion of the surveyor's chain, and observational error.

The Great Survey was so precise that, it determined the Earth bulges at the equator. They compensated for the fact that their plumb bobs did not point straight down, but were deflected by the mass of the Himalayas.

• Anonymous

The current accepted height of 8,848 meters, or 29,028 feet, was arrived at in 1954 by an Indian Surveyor named B. L. Gulatee. Gulatee used the tools available to him at the time, including optical equipment (a theodolite) which can be affected by atmospheric refraction and by the gravitational pull of the mountains themselves. A theodolite is an instrument for measuring both horizontal and vertical angles, as used in triangulation networks. It is a key tool in surveying and engineering work, but theodolites have been adapted for other specialized purposes in fields like meteorology and rocket launch technology. A theodolite consists of a telescope mounted movably within two perpendicular axes, the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a desired object, the angle of each of these axes can be measured with great precision, typically on the scale of arcseconds.

The 1998 American Everest Expedition used GPS (Global Positioning) equipment, which is not subject to distortion.

A GPS receiver was firmly placed in the highest solid bedrock on the summit. The device, along with its data, was retrieved by other climbers approximately a week later.

A review of that data concluded that the long-accepted altitude of Mount Everest — 29,028 feet — may need to be adjusted downward, although not so much as to threaten the mountain's status as the highest on earth.

In fact, one result of the scientific studies last spring was to come away impressed by the work of their 1950's Indian counterparts. "With all our satellite measuring systems and other advantages, our numbers are still within 10 meters of Gulatee's 1954 survey. Everest remains the tallest mountain by a wide margin..."

The contemporary height for the summit would be no more than 8,830 meters, which is a hair less than 29,000', or about 30 feet lower than the current accepted height of Mount Everest."

K2, the second highest mountain in the world, has been measured at 28,250 feet.

But a new "official" height of Mount Everest might in fact mean that no mountain on earth is higher than 29,000 feet.

Modern surveyors use geoid and ellipsoid models to measure high mountains. Those are complicated concepts, but the technically inclined should search for the Dave Mencin's and Charles Corfield's explanation of these models, and on the methodology of last spring's measurements.

I thought they used a measuring tape.

Maybe used a Triangle, that how they measure the distances of Planets, or was. They may have a better way now.