# Means of navigation have changed dramatically

Finding our way across the vast emptiness of the Polar Plateau today is very simple, with the aid of the satellite-based Global Positioning System (GPS). When Amundsen reached the South Pole in 1911, navigation was an entirely different matter.

23 Dec 2007

79.61280 deg S

41.44466 deg E

3668 meters above sea level

Maximum & Minimum temperatures: - 31 to - 38 °C

An antenna on the roof of each of our vehicles continuously receives signals from several of the twenty-odd satellites of the Global Positioning System (GPS). The time-coded radio signals from the satellites allow for very accurate distance measurements relative to the known positions of the satellites, and thus the position of the vehicles can be calculated instantly with an accuracy of a few meters. A screen shows the driver the bearing and exact distance to the point of destination. Aided by this tool, we can head for a chosen point ahead, perhaps a previous observation site marked by a single aluminum pole, and hit it spot on even after hundreds of kilometers' driving through featureless, snowy expanse.

When Amundsen arrived at the South Pole in 1911, navigation was a rather more complicated business. Navigation en route was done by dead reckoning, measuring distance with a distance wheel trailing the dog sleds and taking bearings with a compass adjusted for magnetic deviation - which is large and varying in the polar regions. By the end of a day's travel, the navigator could hope to be within some hundred meters of the intended destination. At regular intervals more exact positions were taken by means of a sextant, a handheld instrument measuring the sun's elevation above the horizon. The solar elevation at noon would give the latitude, while the timing of the solar culmination with a chronometer would give the longitude. Extensive nautical tables and complicated calculations were involved. At high latitudes the process tends to be even more complicated, because the longitudes converge and the solar orbit appears more and more level in relation to the horizon. When Amundsen and his team arrived at what they initially estimated to be the South Pole on December 14, 1911, they eventually found themselves a few kilometers off the target. They spent the following 3 days and nights doing continuous solar observations with sextants and a theodolite, a precision surveying instrument, and eventually closed in on the actual pole with an accuracy of a couple of hundred meters. In 1911 this was quite a feat.

When we arrive at our destination in January, we will be able to drive our vehicles straight up to the target point with no hesitation, and be sure to have parked no more than a handful of meters away from the exact location of the South Pole. That's quite a difference from the meticulous observations and calculations required in 1911!

- Jan-Gunnar & Stein

Glen driving using the GPS (Photo: Jan-Gunnar Winther)