GeneralGPS

How does car GPS systems work and how accurate are they?

Public Comments

1. satellite signals. They are very accurate.
2. The gps gets signals from satellites orbiting the earth. And the accuracy depends on the model of the gps and the quality/amount of signal its receiving. The car ones with a good signal should be accurate within 3 to 5 feet. With a poor signal it could be 20 feet.
3. A GPS system relies on satellites orbiting the earth. They require at least three satellite signals to track where you are and where you're going (hence the phrase "Triangulate your position) GPS systems have come great lengths in the past decade. I have a handheld GPS unit (doesn't have turn by turn directions) and it almost always has less that 100 ft radius of error. (Satellites can't be dead accurate) but on average I'd say it's accurate within 30 feet. As for automotive GPS units, the biggest complaint that I've heard was the many of them don't give correct directions going onto roads that are closed or arent' even there.
4. There are currently 24 GPS satellites orbiting the earth. The GPS used in vehicles triangulates its position with 3 of those satellites(aviation uses 5 and the government uses?????) but they are accurates to within a few feet of the desired position
5. Satellite system, works very well, but if you're paranoid, the government could track you too. Also, in the event of a national security emergency, (terrorist attacks or war) the systems would probably be shut done so they could not be used by the "bad guys".
6. GPS works by using signals from man made satellite. Just imagine if you were to throw a stone into a pond. You can see the waves "propagate" outwards. The longer you wait the further out the waves get (and you can also calculate how long ago the rock was thrown from how far the wave have propagated OUTwards). In similar way GPS calculates it's own EARTH position BACKWARDS using satellite wave propagation. It used to be that GPS was accurate to about 200 feet. But then the US government decided to release more data to make it accurate to about 3 to 10 feet. So it is as accurate as you most probably need it (driving, hiking, hunting, fishing, etc.). I use it to double check the accuracy of my speedo in my cars. Here's a link if you want even more detailed info http://www.howstuffworks.com/gps.htm === Don't forget to vote for the BEST ANSWER - please - whoever it may be. FACT: You also get +3 points when you vote for BEST ANSWER