Danger Angle

These are of two classes, namely, vertical and horizontal. In the former, the offshore distance of the danger is measured with the dividers and this quantity together with the height of the light-house (or hill, etc.), is compared in the distance tables and the angle selected, which will be found given in degrees and minutes. In the horizontal danger angle two prominent objects shown on the chart are selected and a pencil dot is made on the chart seawards of the reer, rock or other danger. A circle is swept with the pencil compasses through the three points. The pencil dot is next connected with the two objects on shore by straight lines and this angle measured by the parallel rules and by the diagram compasses printed on the chart. This angle will be found to be the same at any point of the circumference of the circle. In both the vertical and horizontal angles, so long as the navigator does not allow the angle to increase he will navigate in safety outside of the danger.