The Roots of Marine Navigation - Part I

The history of marine navigation follows that of the early human settlements along rivers, as rivers tended to become one of the first means of transportation of goods. Rough boats and later ships were built across the world- all the ancient civilisations, from the Egyptians to the Chinese to the Mesopotamians navigated at sea. And so did the lesser known Polynesians in the Pacific- it is now believed that they are the oldest ‘open sea’ navigators- all the others were navigating by day and in sight of land at the time- and reached the Californian coast of the present day United States a hundred years before any Europeans.

In the China Sea and the Indian Ocean, a navigator could take advantage of the fairly constant monsoon winds to judge direction

It must be realised that a rough calculation of latitude has been possible since ancient times. There were, for centuries, two major problems. The earlier one was an understanding of direction- even after the advent of the magnetic compass navigators had little idea of direction or accuracy, since the concept of variation was not understood till much later.

The second problem was even more acute. In the absence of an accurate time keeping device such as a chronometer, a calculation of longitude was just not possible. You can read about the use of a marine chronometer here and how it is used to calculate the longitude

Early navigation was problematic and often resulted in the navigator becoming lost, especially when out of sight of land.

click to enlarge

click to enlarge

Rough and ready navigational charts were probably used by the Phoenecians around 4,000 years ago. Early civilisations had no idea about the scale of the charts or the size of the land masses- the importance of a country decided its size shown on the chart, and had no relevance to its actual size. The charts were made on sheep or goatskin and were kept closely guarded and secret

also see http://www.brighthub.com/engineering/marine/articles/23602.aspx

Captains rutters, a record kept by old ship captains of weather, depth of water, routes and everything pertinent to navigation, were a prime source of passing of information from one generation to the next. They were sold for enormous sums because they were the only real source of information, and have been around since the fifth or sixth century BCE.

An Astrolabe or a Cross Staff (see pic, left) was the ancient precursor to the sextant, and used for measuring altitude of the planets or stars, particular the north star. (also see www.brighthub.com/engineering/marine/articles/23287.aspx

Sounding reed, first invented in Egypt, was a hollow tube (reed) which was inserted in river or sea water till it touched the seabed. It used the principle of capillarity to determine the depth of water at a particular location was thus available. Obviously this could be used only in shallow water. More accurate was the lead line (c.13^th Century) see pic right, which was a graduated rope weighted with lead that was concave at the bottom. The lead was coated with wax to bring up samples of the seabed. One way of navigating was then going from one depth to another based on prior experience. A rutter might read, “Go North till you sound 60 fathoms of white sand, then go North again till you get black mud, after which go North East.”

Magnetic compass (c.13th Century) see http://www.brighthub.com/engineering/marine/articles/23373.aspx. The main use of the compass initially was to identify direction of wind. It was otherwise used only in overcast conditions when the sun was not visible. As said earlier, it was extremely inaccurate since the concept of variation was not understood.

Floki Vilgjerdarsson, the Viking who discovered Iceland, always had on board his ships a cage filled with ravens. He periodically let one of the birds free and followed it to land as it flew naturally towards it. If no land was around, the bird naturally circled the ship. Even today, we use this idiom, ‘ go as the crow flies’.

All that mariners had, at this time, was an astrolabe or cross staff, a rudimentary compass and inaccurate nautical charts. There was also a basic understanding of how to get approximate latitude by taking an altitude of Polaris, the Pole Star.

Navigation was dangerous and inaccurate. Columbus’ journal confirms that he could not calculate even latitude properly. Small wonder that he landed up in the Americas looking for India!

In the next article we shall examine the developments from around 1500 AD to the advanced systems of today. A sea change, indeed.