What is the minimum number of Global Positioning System (GPS) satellites that are observable by a user anywhere on earth?

Answer: 4 Satellites

Explanation:

A minimum of four satellites must be in view of the receiver and this is so that four different unknown quantities such as the position coordinates and the clock deviation.

It should be noted that as at today, the total constellation size has thirty three satellites in total with thirty one in orbit and now has an accuracy of a few centimeters