# How does GPS Work? (Video Lesson)

GPS uses a process called trilateration to determine a receiver’s location. Trilateration relies on timing signals from multiple satellites to calculate the receiver’s distance from each satellite. By knowing the position of each satellite and the distance to each satellite, the GPS receiver can determine its position.

A 3D fix is a GPS position that includes latitude, longitude, and altitude. It is calculated by the GPS receiver by measuring the distance to four or more satellites and solving a set of equations. The GPS receiver calculates the distance to each satellite by measuring the time it takes for the signal to travel from the satellite to the receiver.

The GPS receiver then uses the signals from at least four satellites to solve a set of equations that determine the receiver’s position and altitude. The process of solving these equations is called triangulation.

The GPS receiver also uses the information provided by the satellites about their location and the time the signal was transmitted to correct for the effects of atmospheric delay and clock errors. This information is included in the navigation message sent by the satellites.

Once the GPS receiver has calculated its position and altitude, it can display this information to the user, typically on a map or chart. The accuracy of the position fix depends on several factors, including the number and quality of the signals received, the geometry of the satellites in view, and the quality of the GPS receiver.