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Maritime navigation has evolved from using stars and the sun to GPS, which is now mandatory on most commercial vessels. Line of Position navigation is another modern technique that doesn’t require satellites but still has drawbacks.
For millennia, man navigated the seas and oceans using nothing but the stars and the sun, or staying within sight of the earth at all times. With technologies such as the compass, radio, and ultimately global positioning systems (GPS), maritime navigation has become increasingly accurate and reliable, with increasing levels of redundancy in the event of equipment failure. Few would disagree that GPS’s ubiquity, reliability, and simplicity make it the best way to navigate open water.
Ancient Polynesians managed to travel thousands of miles from their home islands in the South Pacific to Australia, relying only on the position of the stars. Navigating the stars, known as dead reckoning, is obviously still a viable option for navigators who know how to do it. Of course, with a clear night sky being a necessity for this technique, it can be a dangerous and unpredictable option. Increasingly, it’s a last resort for all but the most committed traditional sailors and purists.
Around the time of the Renaissance, the invention of the compass and the sextant made travel beyond the sight of earth infinitely more predictable. By measuring a ship’s position relative to that of the sun, the location and heading could be plotted on a map overlaid with lines of latitude and longitude. This was perhaps the greatest advance in seafaring until the age of computers, and made possible the period known as the Age of Sail, for tall ships crisscrossing the globe on military, exploratory, and commercial missions. Like dead counting, hand scribing remains a viable, but complex, tool for the properly trained.
Sea navigation remained unchanged throughout the 19th century, although refinements in existing techniques, maps and charts, and progress in steam propulsion led to improvements in the reliability and speed of ocean travel and navigation. However, since the first GPS satellites were put into orbit in the second half of the 20th century, satellite navigation has become the standard for maritime navigation. Small GPS receivers are cheap and reliable, and can locate one’s position to a matter of feet or meters. GPS navigation is mandatory on most commercial vessels, such as cruise ships, but they are equally essential equipment for hobbyist or hobbyist boaters.
There is another type of modern navigation technique that does not require satellites, known as Line of Position (LOP) navigation. This is, in essence, a highly evolved fusion of classical techniques, using waypoints, known compass headings, and other reference points to determine location and heading. Submarines often use sonar readings in this way to navigate underwater. It’s a good resource when GPS isn’t available for some reason, but it suffers from many of the same drawbacks as dead reckoning, ie a complete reliance on ideal conditions and navigator skill.
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