Have you ever wondered how your sat nav receiver uses satellite signals to calculate your precise location on the Earth’s surface? Here’s a non-technical explanation to satisfy your curiosity. The first factor you need to know is that your receiver has to get a signal from at least four satellites in order to calculate your location. You will find currently about 30 GPS satellites orbiting the Earth, and a minimum of 8 are in a direct line of sight with a given point on the Earth’s surface at all times. So so long as you are not deep underground, satellite reception is rarely a difficulty for receivers.

The only factor your sat nav receiver knows about a single GPS satellite is its distance from you. It determines this by sending a signal to the satellite and receiving a response. Due to the fact radio signals always travel at the speed of light, the delay in response makes it possible for the receiver to calculate how far away the satellite is. But with only a single satellite, your receiver has no way of determining what direction the signal is coming from. In case you picture a sphere centred on the GPS satellite, as well as the radius of the sphere is the distance between it and your receiver, your location might be anywhere on the surface of the sphere.

This is why several satellites are required. Say your GPS receiver repeats this process with a second satellite. You now have two spheres, but since your location is on the surface of both spheres, you can now narrow it down to somewhere along the intersection of these two spheres. The intersection of two spheres is often a circle. But you could still be located anywhere around the circle. So add a third satellite and a third sphere. A circle intersects a sphere at only two points, so you now know that your location is one of those two points. At this point, your sat nav device could simply assume that you’re at the point that is actually on the Earth’s surface and be carried out.

The dilemma with utilizing only three satellites is that the clock in your sat nav receiver is not 1 hundred percent accurate. Becoming off by even a tiny fraction of a second can throw off the calculations, given that such huge numbers are involved. This is why the signal from a fourth GPS satellite is necessary.

If your receiver’s clock were ideal, the fourth satellite’s calculated sphere would intersect one of the two points mentioned above. But since your clock is not excellent, it will be off slightly. In this case, all your receiver has to do is measure the distance between this point along with the surface of the fourth sphere. It then uses this distance to right for any clock inaccuracies. And that is how the Global Positioning Method locates you.

Abe Ford is an expert in Quality Sat Nav Voice and related topics. To learn more, visit http://www.satvoices.com today!