Berlin/Dar-es-Salaam/Heerbrugg – The summit of Mount Everest has already been measured using GPS. Now it is the turn of Africa’s highest mountain, Kilimanjaro, which has been found to peak at 5892 metres above sea level, three metres lower than is shown on the map. This new height measurement* results from a survey expedition by Tanzanian and European experts. Kilimanjaro and Everest represent the culmination points of continental plates, and both mountains are still moving. But how fast, by how much, and in which direction?
Before these questions can be answered, the "starting points" and the three-dimensional shape of the continental plates need to be known precisely. Also, their positions and heights need to be monitored at regular intervals. This has only been possible since satellite surveying, and in particular the global positioning system (GPS), were introduced. So we are on the threshold not only of a new millennium, but also of a new understanding of our planet.
GPS can even help to predict earthquakes
In tectonically-unstable parts of the globe, and particularly in densely-populated areas such as San Francisco, it is not enough to monitor the situation at long time intervals. To measure the height of Everest or to monitor tectonic movements round the clock in Japan, specialists can use the same Leica GPS instruments. Also, Leica MC1000 GPS systems have been mounted directly on the gigantic pillars of the world’s longest suspension bridge, which spans the stormy and 110-metre deep Akashi channel. They monitor the structure in real time with millimetre accuracy and, if substantial positional changes are detected, close the bridge access roads immediately.
The highest was also a first for GPS
The story of GPS summit measurement started in Asia, on Mount Everest. In September 1992, a GPS System 300 from Leica Geosystems was placed on the summit for the first time. A research team of Chinese, Nepalese, Italian and French mountaineers and geodesists, under the direction of the Trieste geologist Giorgio Poretti, redetermined the height of "Jomolangma" (Tibetan for ‘Goddess Mother of the Earth‘) by means of GPS satellite signals.
In 1988, the American geologist Wallerstein suggested that K2 might be even higher than Mount Everest. Years later, Poretti’s "measurement of the century", carried out with both classical and GPS techniques, revealed the height of Everest to be 8846 metres above sea level, 232 metres higher than K2 which also had been redetermined in 1996 by Poretti’s "Ev-K2-CNR"-team.
When Alexander von Humboldt travelled through Latin America in the year 1800, the Andes were considered to be the world’s highest mountains. They rise directly from the edge of the Pacific Ocean, whereas the giant Himalayan range is hundreds of miles from the coast. It was not until 150 years ago, in 1849, when the Englishman James Nicolson first targeted Mount Everest with his theodolite, that the world’s highest point was identified.
Kilimanjaro and the Matterhorn – and a bit of Africa in Europe
What the Himalayas and the Andes have in common is that they are probably still growing. Like the Alps, they result from the collision between continental plates, and magmatic forces in the Earth’s mantle are involved. The Indo-Australian plate is advancing northwards beneath the Asian plate, pushing up the Himalayas. Far beneath the Pacific, currents of magma are parting plates and are forcing the Andes upwards. The fact that the Matterhorn, with its characteristic pyramid shape, is formed of rocks which originated in Africa bears witness to the pressures exerted by the African plate against and beneath the European continent. Further studies are required to explain why volcano Kilimanjaro, measured within the new global ITRF reference system at 5892 metres above sea level, is three metres shorter than the height as recorded on existing maps. Is it really shrinking, or were previous measurements insufficiently accurate? The 1999 survey carried out by European and Tanzanian surveyors provides a reliable basis for further investigations.
Recently, Giorgio Poretti has turned his attention to the Alpine chain and, among other activities, has re-surveyed the Matterhorn. The Leica GPS500 instruments used on the summit and on the Italian and Swiss flanks were the same ones that were used on Kilimanjaro. However, until the results have been evaluated on 16. December 1999 we will not be able to confirm or deny the suspicion of specialists that the Matterhorn, unlike Kilimanjaro, has "grown" further.
* This information was simultaneously released on 25. November 1999 in Dar-es-Salaam (Tanzania) and in Berlin by team leaders John Saburi and Eberhard Messmer and by the scientists and surveyors involved from the University of Karlsruhe, and the Karlsruhe Technical College, and by UCLA in Dar-es-Salaam.
The highest mountains on our six continentsContinentHighest mountainHeight above sea level
AsiaMt. Everest 8846 metres*
AmericaAconcagua 6959 metres**
AfricaKilimanjaro 5892 metres*
AntarcticaVinson massif 5140 metres**
EuropeMont Blanc 4808 metres**
AustraliaMt. Kosciusko 2230 metres**
* First measured with Leica GPS 300/500 during the present decade; Kilimanjaro survey already in new world-wide ITRF reference system.
** Measured with Leica theodolites during the 20th century
