  The great meridian line in the Basilica of Santa Maria degli Angeli in Rome
was built in 1701/1702 with the scope of measuring the obliquity of the Earth's
orbit in the following eight centuries, upon the will of Pope Clement XI.
During the winter solstice of 1701 the first measurements of the obliquity were
taken by Francesco Bianchini. He was the astronomer who designed the meridian
line, upgrading the similar instrument realized by Giandomenico Cassini in San
Petronio, Bononia. The accuracy of the data is discussed from the point of view
of the use of the pinhole.
