How does GPS (Global Positioning System) work ?

Answer 1

It is really cool actually. Ok, so the US gov has put 26 satalites up to orbit the Earth. They are all geosyncranous, (Sp?)so they stay at the same spot over the Earth as it moves. Each of these satallites has an atomic clock on it accurate up to... just really accurate. Then, all they do is broadcast the time.
Now, it is too expensive to have atomic clocks in the GPS recievers, so what happens is that they receive the time from the atomic clock located in Colorado and adjust thier internal clocks everyday so they are really accurate. Then they receive the signals from the satalites. It compares the time that is broadcast from the satalite to the time that it has stored in its memmory and calculates the difference. Since radio transmissions travel at about the speed of light, it can use the time difference to calculate just how far away the satalite is from that possition. It needs a total of at least 4 satalites to claculate where it is in the 3-dementional world we call Earth.
As you can see, it is a relativly simple concept, but the GPS recievers have to be very accurate. Cool stuff though.

BTW, like I said, the GPS satalites are put up by the US Gov, so if they wanted to, they could make them stop broadcasting. Thus, Europe has started to launch satalites of its own so it deosn't have to rely on the US. They won't be operational for a few more years though, but they will be more accurate. (I believe that current GPS recieves are typically accurate up to 9 feet)

Answer 2

Well through triangulation and radio waves. It's quite interesting. You should see some of the new surveying equipment and how accurate it is using GPS. When staking oil wells, pipelines, ect..... you can be no more than I think 3 inches off. Especially with power poles they have to be right in line. But anyway the new equipment gets within a 100th of an inch. It's amazing. Especially when your base is a mile or two away and your within that tolerance on both elevation and distance.
When I was a surveyors hand we would set up a base consisting of a satellite dish and an antenna over a cap marking section lines. You had to level the dish right over these caps placed in section corners. Then you had a dish you carried on a pole. Well the dish you carried, the base, and orbiting satellites would all communicate to form a triangle and put you right where you need to be. Whether it was a corner of a location, a pit corner, a pipe line, center of a road, exact spot to drill for oil, etc..... all within a 100th of an inch.
Well good luck I hope this helped.
Oh and most handheld GPS devices will get you within 10 to 20 feet of accuracy.

Answer 3

There are 24 GPS satellites in orbit, this does change from time to time as spares are launched and older ones fail.

The satellites are arranged in 6 orbital planes 60 degrees apart. Each orbital plane is inclined to the equator at 55 degrees and contains 4 satellites. The orbital period for each satellite is 12 hours. This arrangement gives good global coverage including the poles.

The satellites are tracked by ground stations that compute and predict orbital parameters. The orbital parameters are transmitted to the satellites along with an accurate clock signal.

The satellites broadcast their orbital parameters and the clock signal to users. The user is able to, using the clock signal, to compute the difference in distance to each satellite that it can see. Then, using the orbital data, it can compute the location of each satellite and hence the absolute distance to each satellite. From this information the user can calculate his location on the earth's surface, including altitude.

A location can be determined using 3 satellites, 4 gives a better result if altitude information is required. It is most common to be able to see and decode information from 6 satellites at any one time.

Answer 4

It basically determines your distance from at least three different GPS satellites. There are several up there. It's like you were inside a big triangle and you can always tell where you are if you know how close you are to each corner.

Answer 5

Very well. Signals are transmitted from positioning satellites in orbit and recieved by equipment that uses triangulation and radio frequencies to determine positions on the ground.

Answer 6

Radio Frequencies and triangulation with the help of satellites.

Answer 7

by triangulation.