This is what Nansen says in his book Northern Mists:
The lodestone, or compass, did not reach the Norwegians till the thirteenth century.[229] As to what means they had before[Pg 249] that time for finding their course at sea, Norse-Icelandic literature contains extremely scanty statements. We see that to them, as to the Phœnicians before them, the pole-star was the lodestar, and that they sometimes used birds—ravens—to find out the direction of land; but we also hear that when they met with fog or cloudy weather they drifted without knowing where they were, and sometimes went in the opposite direction to that they expected, as in Thorstein Ericson’s attempt to make Wineland from Greenland, where they arrived off Iceland instead of off America.
G.J Marcus: Hafvilla: A note on Norse Navigation
