GPS
Nature's Final Stronghold
Science expedition places GPS receiver on Mt. Everest summit
By Michael W. Michelsen, Jr.

The highest and mightiest Himalayan peak, Mount Everest, was viewed as nature's final stronghold after explorers reached the North and South Poles. The awesome splendor surrounding Earth's "third pole" beckons boldly. Even veteran English climber George Leigh Mallory called it "Lord of all, vast and unchallenged and isolated supremacy," upon first seeing the peak known to the Tibetans as Chomolungma, or "Goddess Mother of the World." Mallory vanished in his 1924 attempt to reach the summit in his efforts to study the peak, disappearing at about the 27,700 foot level. But on May 20, 1998, 12 American and British climbers reached the summit and placed a Trimble GPS receiver on the top.
    American Wally Berg, a veteran Everest guide from Boulder, Colorado, and Apa Sherpa reached the summit at 9 a.m. Officials reported that the weather was so clear that Berg spent more than two hours on Everest's summit, fulfilling the expedition's science mission of securing a Trimble 4800 GPS receiver on the summit of the world's tallest mountain. Now GPS data is being collected at four points along the mountain-Kala Pattar, Base Camp, the South Col and the Summit-to precisely track the plate movements, horizontally as well as vertically, over time.
    The 1998 Everest Extreme Expedition, organized by geographer Brad Washburn of the Boston Museum of Science, consisted of an expert team of climbers, doctors, and scientists for the Massachusetts Institute of Technology (MIT) and Yale University. The scientific mission to place geological equipment and GPS surveying receivers on the mountain to measure the peak and to conduct experiments in physiology and tele-medicine to determine how the extreme altitudes affects the man and mountain-is as challenging as the mountain itself. The climbers endured climatic extremes that can torture the body and impair the mind.
    Among the tools the climbers took on the climb were Trimble GPS receivers, which not only helped survey the mountain, but also assisted scientists in monitoring the medical effects of the climbers as they ascended the mountain.
    The four Americans climbing Everest were fitted with bio-packs recording how their bodies reacted to the harsh environment. That information, coupled with positioning data from Trimble's Lassen GPS receivers, provided researchers at the base camp with the most detailed information ever compiled on the effects of altitude and climbing. From there, the information was either logged or transmitted by satellite phone to an Earth station in California and transmitted to MIT for further analysis.

A Step Up to the Plates
Due in large part to plate tectonics, that body of knowledge that theorizes that the Earth's crust is made up of an estimated 16 separate plates, which collide and cause such phenomena as volcanoes, uplifts and earthquakes, Everest is moving-horizontally as well as vertically. This geographic arrangement is precisely the reason why there is so much on-going debate about the exact elevation of Mt. Everest.
    "One of the biggest problems scientists have encountered when they try to measure a mountain like Everest is the changing snow and ice level that covers the mountain year-round," said veteran Everest climber Charles Corfield, a member of the 1998 mission. "To really measure the mountain we can't just go to the top and take a GPS measurement. There is an unknown depth of snow and ice on the top of the mountain, which must be taken into consideration. There are even oxygen bottles embedded in the ice at the summit left from previous expeditions, which have distanced themselves further and further from the top because of the thickening of the ice and snow on the summit."
    In addition to the data collected at the summit, the climbers attached weather probes and Trimble 4800 receivers at various points along the summit, providing position and altitude information to within a fraction of an inch. Repeat observations of these stations in the future will allow scientists to determine the true, bedrock height of Everest and monitor its rate of movement.
    "Obviously, on a mountain like Everest, determining where the bedrock is presents a very difficult problem," Corfield explained. "Sometimes, we can only approximate where bedrock is. But using the Trimble 4800 receiver, we can get a more accurate altitude measurement."
    The 1998 climb is not the first time Trimble equipment has been taken to the top. In 1995, Trimble 4000 Geodetic Survey System SSi GPS receivers with Supertrack technology firmware were used to accomplish a three-fold mission: 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 (ft.), and to make GPS observations on the Khumbu Glacier.
    "This time we took another step-to reach the top," Corfield explained. "Only this time we took Trimble's 4800 receiver. The lightweight nature of the 4800 made it easier to carry. Also, the fact that the unit is self-contained with fewer cables made it practical on this trip too. With all of the other equipment that you need to take on a climb like this, who wants to lug more heavy gear with them? Single button operation and the extended life of the lithium battery also made the 4800 more appealing to use."
    Much of the work on measuring Everest was organized by Bradford Washburn, a mountaineer and cartographer who directed the Boston Museum of Science from 1939 to 1980. Although he will turn 88 years old in June, he remains active in the study of Everest's growth, and one of the most vocal proponents of GPS measurement of the mountain's peaks.
    In 1995, the Nepalese government granted Washburn permission to survey Everest using the 4000 SSi receiver, and that year members of his team installed survey markers and an antenna at a rocky area called the South Col [See Sidebar]. The South Col is the site of the highest camp used by climbers before they push on to the summit.
    The South Col receiver activated itself and operated for 12 hours, yielding information on the exact location of that site. It's altitude was measured officially at 25,794 ft.
   In 1997, another measurement was taken at the same site, according to Frederick Blume, a geophysicist at the University of Colorado, and a member of Washburn's expedition. Preliminary measurements indicate that Everest is rising at about one-eighth of an inch each year and sliding northeast about one inch a year. Blume says measurements in subsequent years will help to confirm and refine these changes.
    This year's climb is providing the most up-to-date GPS measurements of the mountain ever made. Measurements made on a rocky ledge known as Bishop Rock, just below Everest's summit, will permit more accurate readings of the mountain's altitude and movement. With the receiver located on the South Col as a known base station, operating equipment on Bishop Rock will provide differential correction, yielding precise measurement from the two receivers tracking the same GPS signals.

About the Author:
Michael W. Michelsen, Jr., is a marketing writer for Trimble Navigation Ltd., Sunnyvale, California. He may be reached at 800-827-8000, ext. 8658.

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