I would like to include an example of such a fix, but it is just too involved and probably meaningless to most readers. We should, however, acknowledge its importance and practical value to people sailing the open ocean. Even though GPS has become the accepted navigation system for most ocean voyages, celestial navigation is a vital skill when technology breaks down. For whatever reasons, many people sailing in unmarked waters are forced to rely on celestial navigation for accurate position fixing. Speed is often very important in calculations for navigation.
Speed is measured in knots .
Knots were originally measured by a line on a reel with knots tied at intervals. The line had a gadget on the end that doesn't let water through. It was let out over the stern of the ship. When the first knot passed over the stern a 14-second hourglass timer was started. At the end of the 14 seconds the number of knots having passed over the stern was the speed of the ship in knots.