Recently Tillerman posted a comment asking how the Vikings navigated? It was a topic I had meant to address a couple of years ago when there was a British Museum exhibition about Vikings.
However the exhibition had been a major disappointment, and one of the reasons for that was it ignored topics like this one.
So how did the Vikings navigate?
One key tactic was to follow a line of latitude, which means head due east or west - and hence know where south and north are.
On a clear night the Vikings would have been able to see Polaris, but in the summer months that far north there was often no darkness, as we found when we sailed to the Arctic Circle.
During the day they could use the length of the sun's shadow if they had created a sun-dial for that latitude and month, but that didn't help on cloudy days.
So they must have had to rely on natural navigation methods, such as using glimpses of sun to measure the wave direction and use that to keep a constant course.
Other techniques were summed up in the phrase on how to reach Greenland from Norway:
From the west country sail west but keep far enough north of Shetland so that the islands are barely visible in clear weather. Stay far enough south of the Faroe Islands so that the steep, high mountains are just halfway up over the horizon. And stay far enough south of Iceland that you can't see land, but you can just about see coast-bound seabirds.
As we were to find out, that is an incredibly useful navigational instruction.
We too saw the Faroe islands from afar (see photo above) and that could indeed be used as a gauge of latitude.
What's more we spent time observing the birds, counting the numbers at the end of each hour of our watches, and we could determine the distance from the coast simply by the number and types of birds we saw.
It would be have been nice to read something about that in the British Museum exhibition, maybe see the writing quoted above or an example sundial but alas no, nothing....