Here's why:

* Trilateration: GPS receivers work by a process called trilateration. This means they use the distance to at least three satellites to pinpoint their location.

* Fourth Satellite for Time: To calculate the distance, the receiver needs to know the precise time it takes for the signal to travel from the satellite to the receiver. The fourth satellite provides the necessary timing information.

While four satellites are the minimum, seeing more satellites improves accuracy and reliability:

* More Satellites = More Data: Seeing more satellites gives the receiver more data points, which helps to refine its location estimate and compensate for errors in the signal.

* Stronger Signal: A receiver with a stronger signal from multiple satellites will have a more accurate and reliable position.

Therefore, seeing more than four satellites is beneficial, but a minimum of four are required for a basic GPS fix.