Editing Global Positioning System (section)

=== More detailed description ===
Each GPS satellite continually broadcasts a signal ([[carrier wave]] with [[modulation]]) that includes:
* A [[Pseudorandom binary sequence|pseudorandom]] code (sequence of ones and zeros) that is known to the receiver. By time-aligning a receiver-generated version and the receiver-measured version of the code, the time of arrival (TOA) of a defined point in the code sequence, called an epoch, can be found in the receiver clock time scale
* A message that includes the time of transmission (TOT) of the code epoch (in GPS time scale) and the satellite position at that time

Conceptually, the receiver measures the TOAs (according to its own clock) of four satellite signals. From the TOAs and the TOTs, the receiver forms four [[time of flight]] (TOF) values, which are (given the speed of light) approximately equivalent to receiver-satellite ranges plus time difference between the receiver and GPS satellites multiplied by speed of light, which are called pseudo-ranges. The receiver then computes its three-dimensional position and clock deviation from the four TOFs.

In practice the receiver position (in three dimensional [[Cartesian coordinate system|Cartesian coordinates]] with origin at the Earth's center) and the offset of the receiver clock relative to the GPS time are computed simultaneously, using the [[#Navigation equations|navigation equations]] to process the TOFs.

The receiver's Earth-centered solution location is usually converted to [[latitude]], [[longitude]] and height relative to an ellipsoidal Earth model. The height may then be further converted to height relative to the [[geoid]], which is essentially mean sea level. These coordinates may be displayed, such as on a [[moving map display]], or recorded or used by some other system, such as a vehicle guidance system.