The Incredible Brilliance Of The Invention Of Auto GPS For Direction Finding
Who would have guessed that the knowledge of how to identify your position based on sighting of the stars could eventually allow us to find our hotel on a business trip? This information journey began with man studying the stars and discovering they were pretty stable in the sky, and that if we account for the movement of the earth, we could reverse the process and find ourselves by looking at them. The auto GPS borrows heavily from the history of navigation.
Navigation has been around since ancient times, but not always in the same format. Early navigation was accomplished mostly by academicians on land, not by sailors who really needed the tool. These brave adventurers relied on the concept of dead reckoning. This is the idea of recording the magnetic direction one is heading and the speed at which one is travelling, factoring in the affect of currents and calculating a position.
The actual method by which that is done is considerable more complex than many recognize. The science depends on several entering arguments; a relative position of an observer, a horizon, and the known star. Fortunately man has been recording and studying the stars since the early Greeks, so their position for any given day and time are known. The relative position of our observer is determined by dead reckoning, which works by itself well enough for the Portuguese to make it back and forth to the new world.
Using modern sextants, when sighting at sunset or sunrise, the measurement had to be taken over time to compensate for the up and down motion caused by swells and waves. Even when the process of sighting the heavenly bodies was perfected for use in aircraft, this time of sighting had to be preserved to account for the movement of aircraft. Since aircraft move much faster than ships at sea, the accuracy of the navigation techniques had to be improved.
With this sextant, celestial sightings can be taken at any time, as it uses a bubble and gravity to show where the horizon is and allow accurate measurements. While the technique is complex and the sextant complex, celestial navigation is considered an archaic method of positioning. To accomplish the sightings, the sextant is inserted into a mount, through the aircraft skin and into the slipstream. With its two power periscope, many stars can be seen, though 57 are normally used for navigation.
When performing celestial navigation in the daytime, the star is obviously the easiest to find, but it yields only a single line of position, so it is less accurate than night celestial navigation. Using three stars located approximately 120 degrees apart in azimuth, it is possible to plot an exceedingly accurate position, even over the ocean, far from land. Unfortunately, the mathematical computations required are an acquired skill and the process is time consuming.
A tremendous step forward in navigation was the invention of the inertial navigation system, which operated by measuring the movement of aircraft in three dimensions. This technology allows for the collection of all the forces acting on the aircraft; thrust, drift and azimuth based from careful calibration of its starting point. It allows for accuracy in location many times better than navigating by the stars and dead reckoning, and can be accomplished by the computer, no navigator needed.
The final step in navigation progress came about with the satellite era. Since these man made celestial bodies have known positions and can be programmed to transmit signals with that information, a receiver on earth can determine the position it is anywhere in the world. Add computer overlaid maps and you can find your way road by road to places you have never been to before.