subject: The Astonishing Genius Of The Origination Of Auto Gps For Direction Finding [print this page] We all remember the days when we went on vacation and spent entirely too much time trying to figure out how to get to our hotel or the attraction we headed out to see. We have also had that sickening feeling of having an appointment or meeting to get to and encountering heavy traffic in an area we do not know very well. The incredible solution is the auto GPS.
Navigation has been an important science for mankind since before all continents were discovered. Since the oceans cover the majority of the earth, sailors needed some way to discern where they were once they had lost sight of land. Necessity being the mother of all inventions, the idea of discovering where they were on the ocean surface could be determined by sighting known stars in the sky.
With all the movement of the ships, it was not a very accurate method, but good enough that experienced sailors could cross the major oceans successfully. Celestial navigation, using the stars to identify the ship position was actually used mostly to confirm the position derived via dead reckoning. Since modern sextant sightings could only be taken at sunrise and sunset, owing to the need for a steady horizon, it was not very accurate either.
The horizon then is the last difficult portion, and limited early celestial observations to sunrise and sunset. With the advent of airplanes, a better system of navigating was necessary as aircraft are subject to directional influences of wind, just as ships were affected by currents, but aircraft are moving much faster, so small heading errors can result in much greater location displacement over the ocean.
The solution arrived at was the periscopic sextant, used up to and including the present day in military aircraft. The device is pushed physically through a portal in the top of an aircraft and locked in place to a mount that has an azimuth. It has a small bubble to help hold it level, and the star or sun is sighted through a two power telescope, with filters for the sun, of course.
Day celestial navigation is actually less accurate, because the computations will only yield a single line of position. At night, the use of three stars selected at nearly 120 degrees of azimuth apart will yield three lines of position which form a triangle. Executed carefully, night celestial positions can plot out in a chart with all three lines crossing in a pinpoint fix.
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.
Finally, satellite navigation uses the notion of using several satellites and comparing the relative location of an observer from them to triangulate a position. With the aid of computers, this position is superimposed over maps to provide a moving directional control device. With the exception of their susceptibility to problems either with the satellites or the reception of satellite signals, auto GPS technology is state of the art.
by: Kim Logan
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