How does GPS work?

2oldman wrote:

ktmrfs wrote:
the more sat's it can access the faster and more accurate you'll get a good "fix".

And yes, my units are usually off during traveling when not needed and it can often take 5 minutes or more to get a good location fix, especially on smaller handheld units.

I read somewhere it usually needs 4 at a minimum.

My stupid Garmin can take upwards of 15 minutes to get a fix, and then I often hear "lost satellite signal." If cell service is available google maps is much better.

needs 4 or more to get accurate location accounting for elevation and determining elevation, My understanding is In a pinch 3 will get reasonable location, but with limited accuracy. with 3 sat's it assumes you are on a flat location at mean sea level.

So for 3 dimensional location (latitude, longtitude and elevation) 4 sat's are needed at a minimum.

if you are moving much above a walking speed, I think it also needs another sat to determine velocity and take into account time and frequency shifts