Navigation and Seamanship (1+1)

1.4.8. Uses of charts

The term bearing and course, are used to indicate directions. The bearing with reference to the direction in which a point, ship, object etc. lies. The course in the direction in which a vessel is heading. Both bearing and course being directions are therefore lines.

To obtain a course : The direction in which a vessel is to be steered or the direction of travel through the water. The course may designated as true, magnetic or compass.

To draw a bearing : A bearing is the direction of a known object and thus determines the direction of the line of sight to that object ; this is the bearing pf the object. He then plots this bearing to the known object on this chart and the ship must be somewhere on this line. This line is called the position line. Bearing may be true, magnetic or compass and instruments such as Azimuth mirror and Pelorus are used to get bearings of known objects.

To Find a position : When two bearings (position lines) intersect, the position of the vessel is said to be fixed. So a fix (position) is therefore the point of intersection of the two-position line. Position is found not only by the bearing but also by Radio bearings, sextant angles, Radar, satellites, altitudes of heavenly bodies etc. The position is indicated in the terms of latitudes and longitudes.