Peary announced in November that an American expedition to the South Pole would be mounted within the next five years.
"View from the North Pole. A base map from 1910 looking down on the earth from the North Pole, to show how the meridians come to a point at the North Pole. Notice that if the 0 meridian were continued, it would unite with the meridian 180. The longitude circles of the Arctic Circle and Tropic of Cancer are shown, with the equator forming the circular outside edge of the map." 
At some point after attending a lecture at the Royal Geographical Society in London given in November 1909 by A.R. Hinks, lecturer on Surveying and Cartography at Cambridge, Amundsen decided that he would adopt Hinks' theory on the subject of determining position near the Poles.
Hinks reasoned that since, as one approaches the geographical pole the meridians of longitude converge and its degrees become ever smaller, this measure eventually becomes meaningless, and that the extra effort in obtaining a measurement of longitude can be saved, focusing instead on latitude alone. 
 Maps etc.
 Wapedia: Polheim. For introductions on latitude and longitude, see for example nationalatlas.gov and the Creative Science Centre's "Finding Our Position on the Earth", as well as the Wikipedia article on navigation.