GPSsatelliitteja

GPSsatelliitteja, or GPS satellites, are artificial objects orbiting Earth that form the basis of the Global Positioning System. These satellites transmit signals that allow receivers on the ground to calculate their precise location, altitude, and velocity. The GPS system consists of a constellation of at least 24 operational satellites, though the actual number in orbit is usually higher to ensure redundancy. These satellites are positioned in medium Earth orbit, approximately 20,200 kilometers above the planet, in six different orbital planes. This arrangement ensures that at any given time, at least four satellites are visible from most points on Earth's surface.

Each GPS satellite carries highly accurate atomic clocks and transmits a continuous radio signal containing information about its orbital position and the precise time the signal was sent. A GPS receiver on Earth picks up signals from multiple satellites. By measuring the time it takes for these signals to arrive, the receiver can calculate the distance to each satellite. Using a technique called trilateration, the receiver can then determine its three-dimensional position. The accuracy of the position is influenced by factors such as atmospheric conditions, satellite geometry, and the quality of the receiver. The system was originally developed by the United States Department of Defense, but it is now available for civilian use worldwide.