How To Improve Android GPS Accuracy By Keeping Time
Especially Helpful Tip For Turn-By-Turn Navigation App Users
The Global Positioning System is a highly sophisticated, and yet taken for granted, navigation system based on data you receive from satellites. This, most people know. For the uninitiated you turn on your iPhone, Android phone, handheld GPS receiver or your car’s navigation system and the satellite tells you where you are on the Earth. The United States invented and launched (satellite pun!) the system as a military application to guide aircraft, missiles, track foreign objects in space and help US Naval captains know where their ships were at sea without using a compass, a map and so forth (let the computer do the work so you can focus on shooting stuff).
Though, the above is not an accurate description of how GPS actually works. The satellite doesn’t send you a signal and say “Oh, I see you at 37.2350° N, 115.8111° W“.
In fact GPS works on a few principles. The first is that a GPS receiver, like the one in mobile phones such as the iPhone and Android phones, receive signals from the satellites (though do not transmit as this would be a more costly chip) and by combining the data received from multiple satellites the receiver can deduce where on Earth the receiver is. This is known as trilateration – not the more common term, triangulation. The receiver only is told where the satellites are – as explained by the Smithsonian Air & Space Museum in a very simple manner;
A GPS receiver “knows” the location of the satellites, because that information is included in satellite transmissions. By estimating how far away a satellite is, the receiver also “knows” it is located somewhere on the surface of an imaginary sphere centered at the satellite. It then determines the sizes of several spheres, one for each satellite. The receiver is located where these spheres intersect.
The Air & Space museum has a page, with diagrams, that explain in much greater detail how GPS receivers determine where on Earth they happen to be – with this notable gem;
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