Refer to figure.
NAVSTAR/GPS is the original satellite navigation system, and uses a constellation of many satellites orbiting the Earth (24 satellites is the technical minimum, but there are spares), with 6 orbital planes used, and at least 4 satellites spaced around each orbital plane. This layout gives excellent coverage around most the world, and allows almost all areas to have access to the required 4 satellites for 3D coverage. In fact there are usually many more satellites available to each receiver, which is useful for more precise data and the option for Receiver Autonomous Integrity Monitoring (RAIM).

The poles are a notable exception, and the satellite coverage at and around both poles is very bad, so GPS systems are not suitable at high latitudes, however, this does not mean that the equator automatically has the best coverage. For the vast majority of the world, satellite coverage is very much "luck of the draw", as the amount of satellites in view will vary from time to time as the satellites pass overhead in their orbits and the Earth rotates below.