In the beginning of the nineteenth century, the price of the chronometers was an obstacle for many poor navigators. Moreover, in those ports that did not operate with time signals, a serious disadvantage of the instrument was encountered when accurate readings could not be calculated. In those circumstances, the navigators, unless they were equipped to observe Jupiter’s moons, had no choice but to rely on lunar distance to determine their position (Williams, 1992:103).

These problems were gradually overcome with the extension of accurate surveys, the use of the electric telegraph and finally radio signals. When radio signals became universal, a wrist-watch with a second hand became sufficient to determine longitude (Williams, 1992:104). The chronometer carrying Greenwich Mean Time on each ship was replaced by a radio receiver which provided a continuously updated time signal from Greenwich in England. This development meant that cheaper clocks could be used in the short periods between signals. With the invention of, and the widespread distribution of inexpensive quartz movement clocks and watches, even the absolute requirement for such radio updates was no longer crucial.

Finally, the current chapter of navigation dispenses with the clock almost entirely, and is concentrating on the widespread acceptance of Global Positioning System (GPS) receivers, most of which are the size of a mobile telephone, and give position to within a few feet anywhere over the planet surface.