Final answer:
A GPS receiver measures the distance between the receiver and three GPS satellites simultaneously to determine the receiver's exact geographic location. The receiver detects the signals from the satellites that are overhead and calculates the position based on the time it takes for those signals to reach the receiver.
Step-by-step explanation:
A GPS receiver measures the distance between the receiver and three GPS satellites simultaneously to determine the receiver's exact geographic location. The receiver detects the signals from the satellites that are overhead and calculates the position based on the time it takes for those signals to reach the receiver. At least four satellites are visible from any spot on Earth, but the receiver only needs signals from three satellites to determine its location. The signals from the satellites are used to triangulate the receiver's position.