| GPS: The Man Who Measured Everest
Eighty-five year old Brad Washburn organizes a team of climbers to survey Mount Everest and gather GPS measurements.
By Paul D. Perreault, Ph.D. The full Khumbu moon lit the ice like frozen lightning as the shadows of our Sherpa guides slipped over my tent. I listened, half awake, to their gentle sounds: the jingle of crampons, the creak of backpacks, the resonant hum of men chanting mantras. Fragrant juniper smoke, incense from their offering fire, seeped inside my tent, and I unzipped the flap to the predawn chill. They gathered nearby to adjust their loads and drink hot milk tea. Then they were gone, winding through the jagged blocks of ice trailed by the fading "Ommmmmmm."
The Sherpas were at work. But this expedition was to be different, not for the men who would risk their lives on the icy slopes of this great mountain, but for their mission. This group of climbers would ascend from this purgatory of base camp, where heaven is below and hell is above, to install two Trimble SSi GPS receivers at locations around the mountain known in Tibet as Qomolangma, or Goddess Mother of the World. To the rest of the world she is known as Everest. The Man and the Seductress
Most people wouldn't blame Brad Washburn if he retired to rest on his laurels. At 85, Washburn has climbed Alaska's Mount McKinley numerous times, including the first ascent of the west side (1951), the first ascent of Mount Baker (1938), and the first ascent of Mount Sanford (1938), all in his pursuit of knowledge. And as if that's not enough, for the past 20 years he has served as founder and director of the Museum of Science in Boston and a patriarch of mountain cartography.
"The one good thing about being 85 is that it's easy to justify taking off and doing the things you really want to do," said Washburn, which in his case meant surveying the world's tallest mountains.
Why not measure Everest, 29,028 feet high, five miles up, the top of the world? Everest is not only the most beautiful mountain in the Himalayan chain, but she has seduced climbers ever since her majestic measurements were first announced in 1852. A century later, on May 29, 1953, a Sherpa named Tenzing Norgay and New Zealand climber Edmund Hillary finally conquered her, which didn't lessen her mystique - especially not to Washburn. Stepping Up to the Plates
His lifelong interest in plate techtonics lured Washburn to begin studying Everest. Plate techtonics, that body of knowledge which theorizes that the Earth's crust is not a solid cover at all, but instead is made up of an estimated 16 separate crustal plates worldwide, each about 45 miles thick and cushioned in a kind of super-slow-motion roil upon a soft, Silly-Putty-like mantle called the asthenosphere. Where the different plates meet, several things can happen, among them volcanos, uplifts and earthquakes. The Himalayan range, of which Everest is a part, was formed by the collision of two continental plates that meet where India and the rest of Asia are joined.
Washburn proposed using a GPS survey system consisting of Trimble 4000SSi Geodetic Survey System receivers with Super-track firmware and 20MB of memory and surveying techniques to measure the growth of the mountain. Thus began years of correspondence between Washburn and Nepali officials for permission to begin his work. In early 1995 Washburn announced the "go-ahead" of his project. The Mission Begins
Washburn's proposed mission was three-fold: to make GPS observations within a survey network to compare with past surveys, to perform the first long-term collection and analysis of GPS measurements above 25,000 feet, and to make GPS observations on the Khumbu Glacier to determine its rate of movement in the vicinity of the Everest Base Camp.
Washburn contacted Trimble Navigation Limited (Sunnyvale, Calif.) prior to beginning his work. His goals impressed Trimble officials, who donated the necessary equipment as well as more than three months of my time to help with the GPS portion of the project. Earlier survey teams had installed survey marks at other locations around the mountain: Kathmandu (6,083 ft.), Namche Bazaar (11,558 ft.), near the Mount Everest Hotel near Syangboche (12,421 ft.), near the Thyangboche Monastery (12,573 ft.), and at the Everest Base Camp at 17,441 ft. To accomplish his mission, the members of Washburn's climbing team installed survey marks close to the summit. (Washburn opted not to make the actual trip.) A survey point was also established at the Everest South Col (25,794 ft.). The GPS receiver was installed at the top of a hill above the village of Namche Bazaar, which gave the instrument excellent visibility of the GPS satellites. The installation is located only feet from the survey mark which has been used for many past optical observations. The GPS receiver would calculate the exact longitude, latitude and altitude of its position, located between northern Bihar and southern Tibet. Armed with these coordinates, the researchers then measured the angles formed by the peaks and receiver stations. Since the length of one side of each triangle and two angles were known, the peaks' heights and convergence rate between India and the southern edge of Tibet that is responsible both for the uplift of the Greater Himalaya and for the great earthquakes that occur beneath them. This year's measurements should reveal this convergence rate to within approximately 10 percent according to Washburn.
While at base camp, the team also installed a survey point in the Khumbu Glacier to measure glacial drift, as well as to serve as a temporary survey mark during the observations to stations near the South Col and the summit.
The GPS receivers had enough memory to store about a month of GPS observations. Compact high precision geodetic L1/L2 antennas with groundplanes were used, and a complement of batteries were chosen to support a variety of survey missions. For receivers to be located at the South Col and the summit where extremely cold temperatures would prevail, 10Ah batteries were used. At intermediate altitudes, long observations were supported by 6Ah batteries and shorter ones by 1.3Ah camcorder batteries for light weight and portability. Due to limitations on personnel schedules, the receivers to be used on Everest and on the glacier were to be left on-site and were operated using their automatic survey timer mode. This mode starts and stops the receivers at the appropriate times to conserve battery power. Methods and Measurements
The most important survey measurement taken by the team during their expedition was that between Namche Bazaar and Everest's South Col. Changes in plans forced climbers to reprogram the GPS receivers to use an automatic survey mode. Radio calls to base camp verified their work. Plans then called for the team to leave one receiver operating automatically on the South Col while they pressed on to the summit. Unfortunately, soft snow and extreme weather forced the team to turn back, just 1000 ft. short of the summit.
Right on time, the receiver located on the South Col turned itself on and logged GPS measurements for 12 hours until it turned itself off. This was the first time any substantial amount of GPS survey data had been collected at or above this altitude. The GPS data was eventually sent to Dr. Roger Bilham of the University of Colorado for processing the data for a final result. In the interim, the data were processed to give the location of the survey mark at the South Col: Location: WGS-84 Latitude: 27#251# 55' 22.590325" Longitude: 86#251# 55' 45.970699" Height: 7861.986m (26,794 ft.)
Unforuntately, the climbing team ran into very deep and soft snow about 1,000 feet below the summit and were forced to turn back. As a result, no GPS data were collected near the summit. A major effort to complete this project all the way to Everest's summit is expected to be completed in May 1992. About the Author:
Paul D. Perreault, Ph.D. (Space Physics, University of Alaska), is manager of University and Government Research Programs for Trimle Navigation Limited, Sunnyvale, Calif. Perreault can be reached by calling 1-800-827-8000, or by e-mail at [email protected] Back |
