His scientific works ranged from astronomy, optics, the problem of finding longitude at sea, cosmology, mechanics, microscopy, surveying, medicine and meteorology.

While determining latitude was relatively easy, early ocean navigators had to rely on dead reckoning to find longitude.

The H.5 is a refined version of his H.4 timepiece, which solved the mystery of how to find longitude at sea.

However, Slocum's primary method for finding longitude was still dead reckoning; he recorded only one lunar observation during the entire circumnavigation.

Jeremy Thacker was an 18th-century writer and watchmaker, who coined the word "chronometer" for precise clocks designed to find longitude at sea.

The aeronauts found themselves, at about eight in the evening, in thirty-two degrees forty minutes east longitude, and four degrees seventeen minutes latitude.

The problem facing both explorers and geographers was finding the latitude and longitude of a geographic location.

The observer's position is somewhere along the position line, not necessarily at the found longitude at the assumed latitude.

Vigan can be found 120 23' 15" east longitude and 17 34' 30" north latitude.

They all helped solve the problem of finding longitude accurately at sea and to chart vast ares of ocean and thousands of miles of coast line.