Avionics
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GPS Pseudorange

Measured distance to a GPS satellite from signal travel time, biased by the receiver clock error — hence “pseudo” range.

Formula

ρ=c (tr−tt)+c δt\rho = c\,(t_r - t_t) + c\,\delta t

Variables

ρPseudorange (m)
cSpeed of light
t_rReceive time
t_tTransmit time
δtReceiver clock bias

Example

Travel time 67 ms: ρ ≈ 3×10⁸×0.067 ≈ 20100 km

Did You Know?

A GPS receiver solves for four unknowns — x, y, z and its own clock error — which is why at least four satellites are needed for a 3-D fix.

gpspseudorangegnsssatellite

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