In a new study in the Proceedings of The Royal Society A, researcher Balázs Bernáth and his team propose that Viking-era sun compasses, whose "lines don't quite match scientists' interpretations," may have had another purpose: calculating latitude. (photo, diagram)
Speculation about Viking navigation is largely based on a fragment of an eleventh-century wooden instrument found in the ruins of a Benedictine convent in Uunartoq, Greenland, which consists of half of a round wooden disc with deep, deliberate scratches. These "gnomon lines" worked much like a sundial to determine orientation.
Bernáth's theory is that the device was not used to determine north, but noon, from which navigators could have learned their latitude. The new theory explains that the instrument had two separate gnomons. "A short, broad one would have been used with the gnomonic lines to help determine noon. A higher secondary central gnomon would determine latitude. In support of this theory, the instrument has an engraved scaling in the northern part that may have aided this second reading."