English clockmaker John Harrison revolutionized long distance seafaring in the 18th century, solving the problem of calculating longitude at sea and devising tools that helped sailors navigate with ...

The Prime Meridian of the World (dotted line) and the modern reference meridian indicating zero longitude using satellite measurements (solid line). Once called the Prime Meridian of the World, the ...

At head of title: Department of Commerce. U.S. Coast and Geodetic Survey. O. H. Tittmann, superintendent. Most of the plates are printed on both sides.

Once called the Prime Meridian of the World, the invisible line running north to south that divides the world into Eastern and Western hemispheres passed through the Airy Transit Circle — a ...