• 168

# Ptolemy

A.D. He estimated the Sun was at an average distance of 1210 Earth radii while the radius of the sphere of the fixed stars was 20,000 times the radius of the Earth.
• 247

# Compass

The compass was invented in ancient China around 247 B.C., and was used for navigation by the 11th century
• 276

# Eratosthenes and Math

B.C.He was the first person to calculate the circumference of the earth by using a measuring system using stades, or the length of stadiums during that time period (with remarkable accuracy). He was also the first person to prove that the Earth was round.
• 325

# Pytheas

B.C. Pytheas is the first person on record to describe the Midnight Sun, polar ice, Germanic . He is the one who introduced the idea of distant Thule to the geographic imagination. His account of the tides is the earliest to state they are caused by the moon.
• 400

# Astrolabe

A.D.The astrolabe is a very ancient astronomical computer for solving problems relating to time and the position of the Sun and stars in the sky.
• Jan 1, 1427

# Prince Henry the Navigator

A.D.In 1427, one of Henry's navigators, probably Gonçalo Velho, discovered the Azores. Portugal soon colonized these islands in 1430.
• Jan 1, 1450

# Anemometer

A.D.An anemometer is a device for measuring wind speed, and is a common weather station instrument.
• Jan 1, 1519

# Ferdinand Magellan

A.D. Magellan's expedition of 1519–1522 became the first expedition to sail from the Atlantic Ocean into the Pacific Ocean (then named "peaceful sea" by Magellan; the passage being made via the Strait of Magellan), and the first to cross the Pacific
• # Sextant

A sextant is an instrument used to measure the angle between any two visible objects.
• # James Cook

Captain James Cook was a British explorer, navigator and cartographer, ultimately rising to the rank of Captain in the Royal Navy. Cook made detailed maps of Newfoundland prior to making three voyages to the Pacific Ocean during which he achieved the first European contact with the eastern coastline of Australia and the Hawaiian Islands as well as the first recorded circumnavigation of New Zealand.Cook joined the British merchant navy as a teen.
• # Ben. Franklin

Franklin became interested in the North Atlantic Ocean circulation patterns. While in England in 1768 he heard a complaint from the Colonial Board of Customs: Why did it take British packet ships carrying mail several weeks longer to reach New York than it took an average merchant ship to reach Newport, Rhode Island — despite the merchantmen having a longer and more complex voyage.
• # Matt Maury

He was nicknamed Pathfinder of the Seas and Father of modern Oceanography and Naval Meteorology and later, Scientist of the Seas, due to the publication of his extensive works in his books, especially Physical Geography of the Sea 1855, the first extensive and comprehensive book on oceanography to be published.
• # Challenger Expedition

Challenger expedition of 1872–76 was a scientific exercise that made many discoveries to lay the foundation of oceanography.
• # Bathysphere

The Bathysphere was a vessel created to explore deep sea.
• # SONAR

Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in Submarine navigation) to navigate, communicate with or detect other vessels.