Nowadays, the navigating officer knows with great accuracy and certainty where the ship is located, what its course and speed are, and which ships are operating nearby. Everything is neatly displayed right in front of him, digitally and interactively. Thanks to the thousands of satellites circling the earth, he can determine his position – anywhere in the world – with extreme precision. That's a big contrast with not all that long ago, before all that satellite navigation stuff came aboard. After all, how do you navigate when all you can see around you is water and sky? Simple: you use the sun, the stars, and the horizon. So before satnav came along a navigator's job was very different from today. He used instruments to determine the angle between the sun or a star and the horizon. That angle told him – approximately – how far north or south the ship was. Early navigators used astrolabes, cross-staffs and Davis quadrants, and later the octant and sextant, which were much more precise.

Sextant Using the sextant, the navigating officer determined the ship's solar noon position every day at exactly noon. He measured the angle between the horizon and the sun when the sun was at its highest. That's only the case for a few seconds, so he needed to work very precisely. Based on the angle indicated by the sextant and the number of seconds it took him to walk to the clock on the bridge, together with information from navigation tables, he could calculate the first altitude line, after which he 'shot the sun' a second time. The ship was at the intersection of those two lines. The day's second measuring moment was at nautical twilight, i.e. dark enough to see the stars but still just light enough to see the horizon. That was also for only a very short time, ten minutes or so. The navigator took three measurements, based on three different stars. He then consulted the navigation tables again, resulting in three lines on the map, which – if everything had been measured exactly right – passed through the same intersection point: that was thus the ship's position.