How many satellites need to be in view for 2D position calculation?

To calculate a 2D position using satellite signals, three satellites need to be in view. The reason for this is that each satellite provides information about the distance from itself to the receiver based on the time it takes for the signal to travel.

When you receive signals from three satellites, you can determine your position on the Earth's surface (latitude and longitude) by triangulation. Each satellite contributes a sphere with a radius equal to the distance to the receiver, and the intersection of three spheres yields a precise location.

In contrast, only two satellites would not be sufficient because they would provide you with a circle of possible positions where the receiver could be located. This ambiguity prevents a precise 2D fix.

A fourth satellite is needed for a 3D position calculation, which adds altitude to the derived coordinates. Therefore, for obtaining a two-dimensional positional fix (latitude and longitude), three satellites are required.