The Greeks and Romans achieved extraordinary feats of surveying in building their aqueducts, tunnels and roads and in measuring the circumference of the earth and the heights of mountains. This book, which contains translations of all the ancient texts on surveying instruments, including major sources hitherto untapped, sets out to reconstruct the instruments and to explain how they were used. The subject has never been tackled before in this detail, and a level of technical sophistication emerges which must count as one of the greatest achievements of the ancient world.