The early ocean voyages were probably big mistakes, a vessel could be thrown off course by a sudden storm or error by the helmsman. So, how did the early sailors navigate the oceans?
Long before the magnetic compass reached Europe, the Vikings were sailing across oceans to both the East and West, discovering new lands in the West such as Iceland and Greenland and even discovering America, nearly 500 years before Christopher Columbus.
These brave Vikings were creative in compensating for their lack of technology. Flóki Vilgerðarson, a great Viking explorer credited with the discovery of Iceland carried aboard a cage of Ravens, when he thought land should be near, he would release one of the birds. If it circled the boat without purpose, land was not near, but if it took off in a certain direction, the boat followed, knowing that the bird was headed towards the land.
The early Pacific Polynesians were the first to use the motion of the stars, weather, the position of certain wildlife species, or the size of waves to find the path from one Island to another.
Imagine one night you call a friend who is a few thousand miles away and ask them to name the star which is directly over their head, you could then find that star in the night sky, and the point on horizon directly below that star would be their exact direction from you at that moment. Unfortunately, a few minutes later that star would have moved and so you would need a new one. With this method it would take a lot of phone calls for every new star.
Fortunately, there is one star in the night sky that does not appear to move, it’s called Polaris, the North Star. The easiest method for finding the North Star is by finding the Plough, an easy to identify group of seven stars, it is known as the Big Dipper to the Americans and the Saucepan to many others.
The Plough rotates anti-clockwise about the North Star, so it will sometimes appear on its side or even upside down, however, its relationship to the North Star never changes and it will always dependably point the way to it.
The first useful invention to help was the Magnetic Compass. With that you could hold a steady direction as you sailed and with something called “Dead Reckoning” (DR), sailors estimated their ship’s speed by noting the time it took for a woodchip, a bubble, or a piece of seaweed to pass along the length of their vessel but since the time was measured with a sandglass, these early calculations were often way off.
To determine a position on Earth’s surface, it is necessary and sufficient to know the latitude, longitude, and altitude. Altitude considerations can of course be ignored for vessels operating at sea level.
If you have a compass, know the date, and have a set of prepared Navigation tables showing how high the Sun should be at local noon, then you can determine your latitude easily but to calculate your longitude, you need oddly enough a very accurate clock which is calibrated to Greenwich Mean Time (GMT). Here’s why- We know that the Earth revolves about its axis once every 24 hours. In other words, the Sun completes its apparent revolution of 360 degrees in 24 hours, so in 1 hour Sun appears to move 15 degrees, in 4 minutes it appears to move 1 degree, in 1 minute it appears to move 15 arc minutes, in 4 seconds it appears to move 1 arc minute, and so on.
If you are sailing, and it’s 1800 hrs GMT, and the local time is 0800 hrs, then you get a time difference of -10 hours, minus 10 hours is minus 150 degrees, therefore, you are 10 hours behind GMT, which means your Longitude is 150 degrees West.
In 1714, the British government offered a prize to anyone who could perfect and demonstrate a clock that would be accurate enough over long voyages to give the desired precision and locating a ship, this type of clock was called Chronometer. But the problem was that all the clocks at that time were mechanical, they were upset by changes in temperature, humidity, vibration, corrosion, etc.
In 1775, Captain Cook returned from a 3-year voyage, having used a chronometer submitted by Larcum Kendall, which was a copy of H4 clock made by John Harrison. Upon comparing it to local reference clocks, it was found to have been accurate to within 8 seconds per day. Nowadays, of course, navigating is much simpler. All large ships today rely on Global Positioning System (GPS). Marine GPS receivers don’t show streets, they give longitude and latitude.
Most ships, even now carry a sextant, a handheld instrument used to measure angles between the Sun, Moon, stars and horizon, as a backup to the GPS Systems. With that and an accurate watch, and navigation tables, a competent navigator can still find where he is on the ocean, even if the modern GPS unit fails.
What do you think, you would have sailed a ship successfully in those times without a GPS or any other advanced navigation equipment? While you think about it, here is an awesome video explaining how the sailors used to navigate in early times.