1975 & 1999 ---
Mt. Everest
Latitude: 27 59 17 N
Longitude: 86 55 31 E
The first record of the height of Mt. Everest was in 1856 that a British Mapping Team established Peak XV at 8,848m (29,028ft) as the highest point on Earth.
In 1975, the Chinese Expedition and Mapping Teams measured the height of Mt. Everest. Chinese Government announced the measurement result as 8,848.13 m (29,028 ft.).
In 1999, an US Expedition Team used GPS (Global Positioning System) technology re-measured the elevation of Mt. Everest —29,035 feet (8,850 meters).
1975 China Summit & Mapping Expedition
In Jan 1975, Chinese State Government and Chinese Army Central Committee decided to summit and mapping Mt. Everest. Two expedition teams - the Mapping team and the Summit team were organized.
On 21 March 1975, 35 geographic mapping commanders and soldiers from Chinese Army plus 11 civil geologists started from the Base Camp (5,400 m, Lonpu Temple) of Mt. Everest to set up 10 Mapping Control Stations along the Mountain. range. They had to complete all the preparing works before the climbers summit Mt. Everest.
On 6th April, 6 members of Mapping team arrived North Col. They completed the measurement of gravity and air mapping point settings at the height of 7,050 m.
Pubu and Xu Tonsen, two Tibetan soldiers of the Mapping team, entered the "High Wind Mouth" at 7,790 m. This was a very sharp range, with 3 sides suspended in the sky. The wind was extremely strong and difficult to stand up. The Gravity instrument in Pubu's hands was shaking and impossible to keep its horizontal level. This young brave Tibetan laid down on the snow at -40 C and 19 km from the highest point of the world; he teased off his gloves, use bare hands fixed the instrument, finally measured the gravity data there. This was the highest altitude in the world.that the gravity data had been taken.
Unfortunately, Pupo's 4 fingers of his hand were frozen and had to be cut off by the surgeon later.
To make sure the precise positions of the mapping stations, when an avalanche happened nearby the East No.3 Station area, despite his sickness, geographic technician Feng climbed 2 miles, faint several times on the way, finally reached East No.3 Station at 6,300 m elevation, and corrected the 3 mm error caused by the snow fall.
In the early morning of 27 May 1975, three red signal bullets appeared on the sky, the summit day started!
While the members of summit team climbing towards the top of the world, the mapping team had been stayed with their 10 Mapping Stations on Mt. Everest for 9 days already and completed all the preparing works. Commander Wang was in the West No.2 Station, two members of his team use telescope watching the climbing process and broadcasting to other Mapping Stations:
"The summit team start climbing . . ."
"They arrived the second stage. There is a sharp range in front . . ."
"They are climbing the metal ladders . . ."
"They turn to North . . . continue climbing up . . ."
"The summit is getting nearer and nearer . . ."
Just at this moment, a massive dark-grey cloud covered the top of Mt. Everest. the figures of climbers disappeared from the telescope. All the members of mapping team jumped by anxious, wanted to fly there and swap off the cloud.
At 2.40 PM, an exciting news arrived from Expedition Headquarter, 9 members of China summit team had reached the top of Mt. Everest at 2.30 PM on 5 May 1975 from north side for the first time.
3 PM, 4 PM, the dark cloud still blocked the view of the top of Mt. Everest . . . 5 PM, 6 PM, the sun started down to the west horizon . . . 6.30 PM, finally the cloud moved down and the sky became blue again. . .
"Notice, the target is appearing!" - A 3 meters long red stick at the highest point on the Earth which was set by the summit team showing itself proudly. The 10 Mapping Stations started their final measurements simultaneously. In a 3 days period, they repeatedly measured all the necessary data and finally obtained the height of Mt. Everest - 8,848.13 m (29,028 ft).
This is an unique story on the history of mountain expeditions. It was performed in a military style in the 1970's. However the courage and faith of these young soldiers were very impressive.
1999 US Mapping Expedition
Twenty-four years later, due to the unstability of Himalayas range, re-measurement of the height of Mt. Everest was performed by the US Millenium Expedition by using GPS technology.
A complete different story. . .
In May 1999. a team of nine, with financial backing from Boston’s Museum of Science, the National Geographic Society, Trimble Navigation, and other donors, completed this task .
What is GPS Technology?
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| GPS Satellite | 3 segments of GPS system: Space segment, Control segment and User segment (click on image to see larger picture) | GPS Satellite |
The system provides highly accurate position and velocity information and precise time on a continuous global basis to an unlimited number of properly-equipped users.
The system is unaffected by weather and provides a worldwide common grid reference system based on the earth-fixed coordinate system.
GPS provides two levels of service: Standard Positioning Service (SPS) and Precise Positioning Service (PPS).
SPS provides, to all users, horizontal positioning accuracy of 100 meters with a probability of 95 percent and 300 meters with a probability of 99.99 percent.
PPS is more accurate than SPS; however, this is limited to authorized U.S. and allied military, federal government, and civil users who can satisfy specific U.S. requirements.
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| 24 GPS Satellites cover the entire regions of the Earth | Global GPS Master Control Stations Network |
GPS operation is based upon the concept of ranging and triangulation from a group of satellites in space which act as precise reference points.
A GPS receiver measures distance from a satellite using the travel time of a radio signal.
Each satellite transmits a specific code, called a course/acquisition (CA) code, which contains information on the satellite's position, the GPS system time, its clock error, and the health and accuracy of the transmitted data.
GPS satellites have very accurate atomic clocks in order to calculate signal travel time. Knowing the speed at which the signal traveled (approximately 186,000 miles per second) and the exact broadcast time, the distance traveled by the signal can be computed from the arrival time.
The GPS receiver matches each satellite's CA code with an identical copy of the code contained in the receiver's database. By shifting its copy of the satellite's code, in a matching process, and by comparing this shift with its internal clock, the receiver can calculate how long it took the signal to travel from the satellite to the receiver.
The distance derived from this method of computing distance is called a pseudo-range because it is not a direct measurement of distance, but a measurement based on time. Pseudo-range is subject to several error sources: for example, an ionospheric delay, and time disparities between the atomic clocks in the satellites and the GPS receiver.
In addition to knowing the distance to a satellite, a receiver needs to know the satellite's exact position in space; this is known as its ephemeris.
Each satellite's signal transmits ephemeris information about its exact orbital location. The GPS receiver uses this information to precisely establish the position of the satellite.
Using the calculated pseudo-range and the position information supplied by the satellite, the GPS receiver mathematically determines its position by triangulation.
The GPS receiver needs at least three satellites with timing corrections from a fourth satellite to yield an unaided, unique, and true three- dimensional position (latitude, longitude, and altitude) and time solution.
The GPS receiver computes navigational values such as distance and bearing to a waypoint, ground speed, etc., by using the GPS receiver's known latitude/longitude and referencing these to a database built into the receiver.
GPS technology on Mt. Everest:
in 1995, a bedrock survey station was established on Everest’s 26,000-foot (7,930-meter) South Col, by using lightweight Trimble GPS receivers, along with lithium batteries that work in temperatures as low as 40 below,
Then, running two receivers simultaneously, one at the South Col and the other at the summit, an accurate altitude could be established for the top of the mountain.
Summit Day Dispatch:
Pete Athans (a climber from the North Face Inc., who holds the record as the only Westerner who has reached Everest’s summit six times).and Bill Crouse reached the summit on May 5, 1999 with five Sherpas carrying the GPS equipment's.
“We climbed through the night so that we could be on top of the mountain to work in the warmest part of the day,” said Athans, “It was pleasant on top of the world that morning, just a little wind and 12°F below. The equipment worked without a problem.”
The GPS equipment once in place at the very top of the mountain, it was able to receive signals from GPS satellites. Running in tandem with the receiver at 26,000 feet (7,930 meters) on the South Col, the receiver on the summit was able to give an exact altitude and position for the top of Everest. The measurement was taken place on 5 May 1999 for 50 minutes.
Calculating the revised elevation of Everest involved Roger Bilham of the University of Colorado.
Boulder, two of his students, David Mencin and Frederick Blume, and Kristine Larson, of the aerospace engineering sciences department of the University of Colorado.
Charles Corfield of Palo Alto, California, was the science manager.
Also working closely with this team were two world leaders in the field of Himalayan geodesy: Muneendra Kumar of the National Imagery and Mapping Agency (NIMA) of the United States and Jun Yong Chen, Senior Advisor to the National Bureau of Surveying and Mapping of China.
Announcement of New Height for Mt. Everest:
The revised elevation—29,035 feet (8,850 meters)—was announced on 11 November 1999 by Bradford Washburn, renowned mountain photographer/explorer and honorary director of Boston’s Museum of Science, at the opening reception of the 87th annual meeting of the American Alpine Club.
Washburn said the reading of 29,035 feet (8,850 meters) showed no measurable change in the height of Everest calculated since GPS observations began at the South Col four years ago. But from GPS readings from the South Col over the past four years, with the receiver being attached to the same steel bolt fixed permanently into the rock face, it appears that the horizontal position of Everest seems to be moving steadily and slightly northeastward—between 6 centimeters (2.4 inches) a year.
"But remember that even these figures are subject to change—by a lot and at any moment—as they are directly dependent upon the behavior of the great thrust-fault system that is shoving India under Nepal and China to create the Himalaya."
This latest data had been received “with enthusiastic approval” by the U.S. National Imagery and Mapping Agency and China’s National Bureau of Surveying and Mapping.
The National Geographic Society has accepted the new elevation 8,850 m (29,035 ft) for Everest as new official data and has updated its flat wall map of the mountain.
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