For GPS navigation, how many satellites must be in view to determine a precise location?

To determine a precise location using GPS navigation, a minimum of four satellites must be in view. The reason for this requirement is that each satellite provides a specific distance to the receiver based on the time it takes for a signal to travel from the satellite to the receiver.

With signals from three satellites, a receiver can determine its position in two dimensions — latitude and longitude. However, to accurately calculate altitude as well, which fixes the position in three dimensions, a fourth satellite is necessary. The additional satellite helps to correct any timing errors in the receiver's clock, which is crucial for accurate distance calculation. This trilateration process enables the GPS to pinpoint your location within a three-dimensional space.

Therefore, while fewer satellites can yield a less accurate position or just a two-dimensional fix, engaging with four satellites establishes a reliable three-dimensional fix for precise navigation.