At 02:19 PM 9/16/96 METDST, you wrote: >Dear sundial subscriber, > >Someone suggested earlier on this list that a sundial on the >southpole would have some interesting features. > >This made me think of a question that I have had for a >long time and up to now, I did not find anyone that had >a sufficient answer: >" How and with what accuracy did the first travellers > to the North and South Pole > estimate the distance to the Pole, and > how did they know that they reached their goal? " >As Pole travel is usually conducted in summer >for obvious reasons, the only astronomical companion >of the travellers is the sun. >This explains why I come to this mailing list with this question.
The North Pole was reached on Sep 6, 1909 by American Robert E. Peary and his companion. I do not know much details about this expedition. The South Pole was reached by Norwegian expedition led by Roald Amundsen on Dec 14, 1911. I read his book on the subject. For navigation they used marine sextants and artificial horizons and geodetic instrument called theodolite (I guess the name) and few marine chronometers for time keeping. For everyday navigation they used compasses and measuring wheels attached to sledges that "logged" the covered distance. Whenever weather was fair they took few times a "day" Sun's altitudes to determine position and compass error. Amundsen had rank of sea captain and few of his party were also experienced sailors so navigation for them was not a problem. During polar day Sun is a very convenient body for measurements, it sweeps all possible azimuths within 24 h allowing to choose well lines of position you need. The accuracy they could achieve was to about or below of 1/2 of Nautical Mile (1852 m) if they performed a series of sights. The day Dec 14 (Amundsen mentions Dec 15 in his book possibly because he kept as their standard time the time of their base Framheim on Antarctic coast) they reached their first approximation of the Pole. This day is assumed by as the day of "taking the South Pole". Next "day" Amundsen sent three of his companions to make 20 km walks in three directions just to be sure that the Pole was within the triangle they made. He himself and another his companion stayed on the spot and performed very careful series of sights which showed them that they were off the Pole by about 10 km which was caused by "course" error during the last walk. When all his companions came back they made those missing 10 kilometers on Dec 17 and assumed that they were on the Pole. They set the tent and the flag on the spot found few weeks later (Jan 18, 1912) by heroic and tragic Scott's expedition. They determined the Pole with accuracy I think of few hundred meters. The book: Roald Amundsen - "Die Eroberung des Sudpols" this is the Norwegian original, I read Polish translation "Zdobycie Bieguna Poludniowego" and I know that German translation exists because the Polish one was done from German (very few Polish speak Norwegian and vice versa). I do not know about English versions. >Is it possible to determine the height of the sun >with an accuracy better than one arc-minute >(corresponding to a distance less than 2km), >with an apparatus that can be carried and used >in a polar and mountaneous environment? >Or was there another way of determining the location? > >I would be happy to know your idea about this question. > Classic marine sextants enable measurements of altitudes (and other angles) with accuracy of few tenths of a minute of arc. Time keeping today is no problem. So we may have accurate position using classic methods. Sattelite systems like GPS give accuracy (for civil use) of about 200 m. The problem with geographical poles is that they move, not so wildly as magnetic poles, but they still move. This is because the Earth is not a rigid body, so changes of moments of inertia caused by internal movement of masses bring movement of axis of rotation relative to the Earth surface. Today astronomers track those changes very accurately by constant measurement of latitudes of few observatories laying approximately on opposing meridians. The changes are not big, poles travel in an area of about 20 m if I remeber well. - Slawek Grzechnik
