about how the GPS System

Basic understanding about how the GPS System

As I promised in the recent entry talking about the agenda for mobile Ham GPS, I will try to explain how "roughly" the guidance that we all know as GPS. I think it may be a topic of interest and that many people will be asked once. And warn you that I will not enter into technical details or anything like that, because what we want is that it captures the idea of a global understanding of how this complex system.

GPS stands for Global Positioning System that is "Global Positioning System" and consists of a network of 24 satellites that broadcast a series of signals simultaneously, which once interpreted by a receiver give us our position in three dimensions at any point of the world, our speed and our guidance. Obviously, the GPS system is not covered in those places that do not reach the satellite signals, so you will not have any utility underground, inside buildings and the like, but in any place visible from the sky can be able to guide us smoothly through the system.

To understand how the system should know that the GPS satellite network are spread across the Earth's orbit about 20,200 km of high and there are about 30 of them (24 are needed, but there are several "reserve") spinning tirelessly to land. It follows the basic principle that a GPS receiver to know where is the triangulation of signals received from three or more of these satellites to receive the signal from a satellite receiver knows the time it takes to get that signal and therefore the distance to that found that satellite. That fact alone will not give many clues about where we are, as the area covered is large. However, if we receive the signal from three satellites and the receiver will be able to know in what position is in latitude and longitude, and in the event that the signals coming from four or more satellites also can know the height to we are.

Simplifying the issue a bit, we can say that the problem is reduced to a calculation of spherical surfaces (whose center is the position of the satellite radio and the distance that we are) that intersect with each other, which is solved with four areas get a spot, though the GPS needs only three of them to stand on the land through a "trick" used and that is to discard one of the two points earned by making the intersection of three areas.

Obviously the system is not as simple as reading the signals, and is triangular, as the recipient receives positioning satellites to see what is on it at every moment, we must address the issue of perfect synchronization of the clocks Satellite and receiver because the signals travel at the speed of light (an error of one thousandth of a second would be an error of 300 km).

The GPS systems: an example of large-scale engineering. I find it incredible that receive the signal from satellites to approximately 20,000 km altitude we can accurately know our mistake with these meters. Is not what you look like you too?