History of navigation and GPS
Navigation before GPS was not only possible but also reliable
Modern GPS navigation has been in use but a couple of decades, yet the art of locating one’s position has a history that long predates the advent of the satellites. Nowadays, even among professional mariners, there are those that no longer understand how to navigate without modern instruments. However, even in this age of GPS-capable smartphones and navigation devices, it may come in handy to remember what to do if you are unable to obtain a signal from the sky or the battery of your pocket device has died.
Lighthouses and maps have already been in existence for hundreds if not thousands of years. Wayfarers took their bearings by the lay of the stars in the night sky and ancient mariners kept their vessels within sight of shore avoiding the high seas. Light boats were enough to settle the Pacific Ocean islands which are sufficiently close to each other and blessed with an abundance of clear night skies over the surrounding ocean waters.
Thousands of years ago, the early sailing vessels would cross the South China Sea and the Indian Ocean by taking advantage of monsoon winds which always blow in the same direction as long as the season lasts. These favourable winds made it possible to cross the open seas twice a year without fear of getting lost. At the same time, the Icelanders living far up north used the light-polarizing property of a special rock (the sunstone) the surface of which when polished smooth revealed the position of the sun even under a clouded sky, a weather condition relatively common on the northern seas. The position of the sun also allowed approximate estimation of direction and location.
Compass – a relatively recent invention
The compass, which to our modern age seems an incredibly simple tool, was invented in China relatively recently – a few hundred years before Christ – and was introduced in Europe by Persians only in the 13th century. The magnetized needle of a magnet compass is mounted on a pivot point which allows the needle to turn freely and align itself with the Earth’s magnetic field which determines the needle’s north-south orientation. Compasses and cartography considerably facilitated sea travel and exploration of wilderness ―maps gained in accuracy and even the Estonian coastline assumed a recognizable shape on medieval sketches.
The North Star―how can it help you find your bearings?
An ancient and reliable method to find one’s bearings in the wild when no compass is available is by reference to the North Star. This bright star that shines in the night skies of the northern hemisphere appears to sit above the Earth’s north celestial pole throughout the year and allows to determine the direction of true north. Once we have located that star, we can also determine the latitude of our position—the altitude at which the North Star is observed above the horizon roughly corresponds to the latitude of the observer.
A long exposure star trail photo reveals that everything rotates around the North Star. This direction is the true north and the altitude between the star and the horizon equals the latitude of the observer. Photo: (CC) Kevin Hadley / Wikipedia
Precise determination of one’s longitude and latitude also requires the exact measurement of time, performed until the 16th century by hourglass or clepsydra (a water clock). Finally, in the 1760s, a marine chronometer was created which could work reliably on a rolling and pitching vessel and allowed the determination of geographical position in any weather.
The sextant – high-precision angle-measuring navigation instrument
The sextant only became part of the navigation equipment in 1757. It is still used as a back-up when there is a power outage out or when electronics fail. It allows to measure – with considerable precision — the angle between a celestial body and the visible horizon and, based on that measurement and the exact time that it was made, to calculate one’s latitude. In clear nights, it is possible to use the North Star to find one’s directions and to determine one’s latitude.
The sextant is essentially an optical instrument that, by means of mirrors, allows to combine the images of two objects in a single visual field. The position of the mirrors is adjusted with the help of an adjusting worm such that the position of the celestial object observed is projected to the horizon in the sighting tube. The numerical value of the angle measured is then read from the drum of the adjusting worm. As this description shows, measuring the angle is a rather straightforward procedure. It is the calculations involving time that present more difficulty.
Radio waves guiding the way
In 1906 for the first time a seafaring vessel was fitted with a device which, by mechanical rotation, could accurately determine the direction of a radio signal. Thus, the first radio beacons appeared, capable of reaching ships yet behind the horizon and of guiding them to port.
In 1930s, the first automotive navigation systems appeared. Yet, these were not the high-tech wonders we are accustomed to nowadays – their first appearance was in the form of simple map rollers mounted on the car’s dashboard where they could be turned by the front seat passenger to reveal the directions to the next waypoint.
World War II spurred the development of the early long-range radio navigation system LORAN whose four stations provided guidance to the ships on the east coast of the United States and Canada.
The first communications satellites launched already a few years after Sputnik
The age of satellites may be said to have begun in 1957 when Sputnik 1, the world’s first artificial satellite, was launched into the Earth’s orbit by the Soviet Union. It then took until 1962 for a solution that resembles GPS navigation to emerge: although doing it very roughly, the seven satellites of the TRANSIT system facilitated the determining of ground locations. Compared to the compass and sextant, the new system was faster and more reliable.
From this point on, the accuracy of satellite navigation has improved continuously. On 1 May 2000, by decision of the US military, the accuracy of civilian GPS receivers was upgraded from several hundred to several metres. Today, we can already enjoy the accuracy of one metre in our GPS-capable smartphone or smartwatch, or a separate navigation device. This is usually quite enough for finding your way or the desired location.