Navigation.

-->

'Were the Nabataeans Really Sea Going? How the Nabataean people took to sailing ships? The speed at which they did this might be considered remarkable, if it were not for the fact that navigating in a featureless desert is very similar to navigating on a featureless ocean'

'The basics of this navigation, whether it be used on the high seas, or in the depth of the Arabian desert.'

'However, not all Arab tribes knew how to navigate by the stars. Indeed, only a very few had this skill, as even today only the Slayb tribe are known as the trackers and guides in the desert. (See: Where are the Nabataeans Today?) Many early sailors sailed along the coast, always keeping land in site. In this way, they simply harbor-hoped along the coast. One wonders what sea captain would have committed himself to the emptiness of the open sea without a knowledge of navigation by the stars. It would seem a small step however, for desert traveling Nabataean merchants to move on to being ocean traveling merchants, if they had the occasion to own ships and the need to transport goods by them.'

'Modern navigation includes three aspects. Finding latitude, longitude and accurate time-keeping. By knowing one's location and the speed of their travel a person can accurately navigate across featureless landscapes.'

'qiyas 
Before the invention of the compass, watch, and the sextant, the mariner's main guide was latitude. To obtain their latitude, Arabs measured the altitude above the horizon to a known star, and then deduced from this the altitude of the Pole Star, (since the Pole Star was the one star that did not move in the sky). In some cases ancient navigators measured directly the altitude of the Pole Star. This was the simplest method, and was known as the science of qiyas. The easiest method was to use the width of a finger. When held at arm's length, the width of four fingers was considered to measure 4 isba'. In a 360 degree circle there were 224 isba'. It was considered that a day's sailing due north would raise the Pole Star 1 isba' from the horizon. For those traveling on land, the isba' was further divided into 8 zam. Thus land distances were often measured in zams.'

'kamal 
A more accurate, but still simple instrument was known as a kamal. This was a small parallelogram of horn or wood measuring about one by two inches with a string inserted in the center. On the string were nine knots at measured intervals.'

-->

The end of the string was held in the teeth. The lower edge of the horn was placed on the horizon while the horn was moved along the string until the upper edge touched the required star. The knot at which the horn covered the exact distance signified a certain number of isba' of altitude of the star. The altitude of the Pole Star could then be deduced from the rahmani.

-->

An alternative way of using a kamal was to move the knots through the teeth until the piece of horn or wood covered the required star altitude.

Vasco da Gama's pilot from Malindi used a kamal, and the Portuguese adopted it and eventually modified the spacing of the knots to measure degrees.

Sometimes Arab and Indian seamen added extra knots marking the latitudes of particular ports of call, or they simply used a kamal on which all the knots indicated particular ports of call.

(unknown) 2002 [online]  Available at: http://nabataea.net/sailing.html