Convert from span to furlong [survey]

Unit Definition (span)
Span is the width of a human hand, from the tip of the thumb to the tip of the pinky finger.

Unit Definition (furlong [survey])
A furlong is a measure of distance within Imperial units and U.S. customary units. Although its definition has varied historically, in modern terms it equals 660 feet or 220 yards, and is therefore equal to 201.168 metres. There are ten chains in a furlong and eight furlongs in a mile. The name "furlong" derives from the Old English words furh (furrow) and lang (long).