Age of Discovery, Tools of Navigation

Navigation is the science of finding your way. Today people use navigation to find their way at sea, under water, in the air, in space, and on land. But originally "navigation" referred only to finding your way at sea. The word "navigation" comes from Latin words meaning "ship" and "move."

Today’s ships have high-tech navigational tools and systems. But during the Age of Discovery (1400s–1600s), navigation was primitive. Navigators used—and improved—tools and methods that had been developed centuries earlier.

Early Navigation

Before the Age of Discovery, ships rarely sailed far from the coast. A navigator could establish his location by looking at the shore. If he recognized a mountain or beach, he knew where he was. Finding your way by using such landmarks is called piloting.

Pilots away from the coast had another way to figure out where they were. They could "take a fix" (find their position) with dead reckoning. In this method, the navigator simply kept track of the ship’s direction and speed since the last fix. Then he made corrections for winds and ocean currents. (These may have forced the ship off course.) From this information, he could take a new fix.

Early navigators also guessed their position by following the stars. This is called celestial navigation. The navigators could determine their latitude, or north-south position, by seeing how high in the sky a particular star was.

The easiest star to navigate by was the North Star (Polaris). It is always just above the North Pole. It can be seen from anywhere in the Northern Hemisphere. Using the North Star, a navigator can keep a steady course east or west. All he has to do is make sure that the North Star stays at the same place above the horizon. In the Southern Hemisphere, a constellation called the Southern Cross is used the same way.

Tools for the Age of Discovery

The Portuguese led the way in improving navigation. Foremost was Prince Henry the Navigator (1394–1460). His support led to better maps, charts, and navigational instruments. He even built an observatory for the study of astronomy and navigation.

Some early tools were around in ancient times. These were simple but useful. The sounding pole was a simple stick; sailors pushed it down into the water to see if it was deep enough to sail through. The log was a block of wood. Sailors would drop it into the water at the front end of the ship. Then they would count how long it took the log to reach the back. From this, they could figure out the ship's speed. Navigators kept a careful record of the ship's speed and direction. Such records are still called the ship's log.

One early tool was the magnetic compass. The compass had been invented in the 1100s. When the sky was cloudy or overcast, mariners (sailors) could not use celestial navigation. The compass gave them another way to determine their direction.

The first compass was a small magnetized iron needle. The needle was stuck in a piece of straw and floated in a bowl of water. The mariners found that the needle always pointed in a northerly direction. They thought the compass was inaccurate. They did not know that the compass pointed to Earth’s magnetic north pole. (That is slightly different from the geographic North Pole.)

Navigators also used the quadrant to find their latitude. This device came into use around the 1300s. It was made of a piece of flat wood or metal shaped like a quarter circle. A scale was drawn on its rounded edge. The navigator sighted a star through holes in the instrument. The star's height above the horizon could be read from the scale. From that, navigators calculated the ship’s latitude.

Similar to the quadrant was the astrolabe. This tool was a heavy metal disk marked with a scale around it. It also contained a star map. This device also measured the angle of the Sun and stars above the horizon.

Even using these instruments, navigators could not be sure exactly where they were. They could estimate the ship’s latitude. But they could not accurately determine the ship’s longitude—its east-west direction. This would not happen until 1764, when an accurate timekeeping device was invented.

Navigators in the Age of Discovery used primitive tools and small ships. Still, they were able to make remarkable voyages. They opened up trade routes between Europe and Asia. And they discovered the Americas.


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SOURCE: The New Book of Knowledge


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