Until advances in the late twentieth century, navigation depended on the ability to measure latitude and longitude.

As soon as sailors lost sight of land they had no ability to measure longitude and were consigned to flying blind so to speak.

Scientists and navigators had been working on the problem of measuring longitude for a long time.

This brought the problem of measuring longitude at sea into sharp focus once more.

The man who discovered how to measure longitude.

However, as it was not possible at the time to correctly measure longitude, the exact boundary was disputed by the two countries until 1777.

He also devised a method for measuring longitude, based on eclipses.

A crater named Anat provides the reference point for measuring longitude on Ganymede.

In order to accurately measure longitude, the precise time of a sextant sighting (down to the second, if possible) must be recorded.

In 1674 he knew that the most perplexing problem facing the great seafaring nations of the 17th century was measuring longitude.