At intermediate stops, they had to estimate their distance and orientation relative to their starting point, but without being able to see or pinpoint its location. (sciencedaily.com)
Currently, with 12 stations planned on two lines reaching from Torino and Venice down to Salerno, the network offers active service from Milan - Naples, with intermediate stops in Bologna, Florence and Rome. (breakingtravelnews.com)
Of course other considerations, such as intermediate stops, are important for air traffic, and the Earth is not a perfect sphere. (newscientist.com)