Satellite navigation

Satellite navigation determines position, speed, or time from signals transmitted by orbiting satellites. Receivers usually calculate their location from signal travel times measured against satellite clocks.

Trilateration: A geometric method for locating a point from its distances to known points. A receiver intersects satellite-distance measurements to estimate its location.
Global navigation satellite system: A satellite constellation and supporting infrastructure that provide global positioning, navigation, and timing services. Satellite navigation is commonly delivered through these coordinated systems.
Global Positioning System: The United States satellite navigation system, commonly known as GPS. GPS is the best-known operational example of satellite navigation.
Inertial navigation system: A navigation system that estimates motion from accelerometers and gyroscopes without external signals. It continues tracking through satellite outages but accumulates drift over time.
Multipath propagation: The reception of a signal along multiple paths after reflection, diffraction, or scattering. Reflected satellite signals can distort ranges and shift a position fix.
Pseudorange: An apparent distance calculated from the travel time of a received satellite signal. Satellite clocks and receiver-clock error make measured ranges imperfect distances.
Radio navigation: Navigation that determines position or direction using radio signals. Satellite navigation is a space-based form of radio navigation.
Galileo (satellite navigation): The European Union’s global satellite navigation system. Galileo provides an independent constellation for positioning and timing.
Dead reckoning: A method of estimating current position from a previous position and measured movement. It can bridge signal gaps, but errors grow as movement estimates accumulate.
Radio-frequency interference: Disruption of radio reception by unwanted electromagnetic energy. Interference can weaken or overwhelm the signals used for navigation.

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