Finding the Way

Navigation is the craft of knowing where a vessel is and how to get where it is going.

Dead reckoning and piloting

Dead reckoning estimates position from a known starting point, course, speed and time. Currents and wind make it drift from reality, so navigators correct it with fixes. Near land, piloting uses bearings to charted landmarks, depth soundings and aids to navigation.

Celestial navigation

Latitude can be found by measuring the angle of the sun at noon or of Polaris above the horizon. Instruments improved from the astrolabe and cross-staff to the quadrant, octant and sextant. Longitude was harder: it requires knowing the time at a reference meridian. The British Longitude Act of 1714 offered a prize for a practical method. John Harrison's marine timekeeper H4 was tested on a voyage to Jamaica in 1761–62 and performed well; marine chronometers became standard in the nineteenth century.

Electronic navigation

Radio direction finding, LORAN and other systems followed in the twentieth century. The U.S. Global Positioning System became fully operational in 1995; other satellite systems followed. Radar, AIS (automatic identification of other ships) and electronic charts are now standard.

Why the old skills stay

Satellite signals can be lost, jammed or spoofed. International training standards still require watchkeepers to understand position-fixing, compasses and charts. A good navigator checks one source against another.

Programs

Maritime Crew (deck/engine). Credentials: STCW Basic Training; USCG Able Seaman.