ASA 105: Skill 9, Measurements
9. Measurements: Convert courses and bearings between true, magnetic, and compass. Determine Latitude and Longitude. Measure distance. Nautical measurements on a chart are either Angular or Linear . Courses are angles and distances are linear. The other vital nautical measurement is Time given in hours and minutes. Leading lights, such as this pair in Nantucket, are a guide for staying in the channel. They may be used to check you compass deviation. In that instance we use a line, the range, to correct an angle, compass deviation. The first measurement for navigators is True North. The longitude lines on the chart are North/South lines. The North Pole is an absolute. Compasses, however, don't point at the North Pole, they point at the Magnetic Pole which shifts ever so slightly each year. The inner rose of the compass rose printed o a chart represents the Magnetic Pole and shows the Variation from True North. Com...