Jewel of Muscat Education

Navigation in the 9th century

A thousand years ago navigation at sea was more an art than a science. Today, few sailors would contemplate a voyage without a compass and charts. Yet well before Europeans were exploring the world, Arab sailors had successfully crossed oceans without conventional navigational tools.

Arab navigators were famous for their great powers of observation and sharp memories. They used all their senses to observe the colours and patterns of the sea and the sky. They also used the sun, the moon and the stars to find their way.

When the Jewel of Muscat leaves Oman on the voyage to Singapore the crew will have modern navigational equipment to monitor the ship's performance. However they will also experiment with some of the ancient techniques used by Arab navigators.

Measuring latitude

Celestial navigation is the science of finding your way by the sun, the moon, the stars and the planets. Humans have been finding their way using the sky for thousands of years.

For at least two thousand years, navigators have known how to determine their latitude — their position north or south of the equator.

At the North Pole, which is 90 degrees latitude, Polaris (the North Star) is directly overhead at an altitude (a height) of 90 degrees. At the equator, which is zero degrees latitude, Polaris is on the horizon with zero degrees altitude. Between the equator and the North Pole, the angle of Polaris above the horizon is a direct measurement of latitude.

To measure their latitude Arab navigators made a simple instrument called a kamal. This is a small rectangular wooden card with a string attached through a hole in the middle. Before leaving his homeport, the navigator would take his kamal and putting the string in his teeth, look towards Polaris. He would then stretch out his arm, keeping the string tight, to the position where he could see Polaris at the top of the kamal and the horizon along the bottom. He would then tie a knot at the point where his teeth touched the string.

To return to his homeport, he would sail north or south as needed, observing Polaris with the kamal and with the knot between his teeth. At the point where the star was on top of the kamal and the horizon was on the bottom he would turn towards home knowing he could sail down that latitude to his homeport.

Over time, Arab navigators started tying knots in the string of the kamal at intervals of one isba (or issabah). The word isba is Arabic for finger and it measures an angle of about 1.5 degrees, or approximately the same as a finger width on an outstretched hand. For the ports they visited frequently, they would tie a knot on the string of the kamal to correspond with the altitude of Polaris for that location.

Did You Know?

Polaris stays almost motionless in the sky, and all the stars of the northern sky appear to rotate around it. Therefore, it makes an excellent fixed point from which to draw measurements for celestial navigation in the northern hemisphere.