Concepts · not live data
Learn
How satellite navigation works: signals, pseudorange, clock correction, and why four satellites are enough. Live broadcast metrics are on the status dashboard.
1 · Pseudorange
Your receiver measures time of flight × c. Wrong receiver clock makes the range look too long or short, that biased number is the pseudorange.
- True range
- 20.200 Mm
- Clock bias (×c)
- +120 m
- Pseudorange ρ
- 20.200 Mm
2 · Broadcast clock correction
ISRO uploads af0, af1, af2 in the nav message. Receivers apply the same polynomial NavIC uses, our monitor reads it from IGS files.
Δt = af0 + af1·Δtsec → error ≈ c·Δt
After Δt = 2 h (typical update spacing)
Δt = 2.214e-8 s
Range error = 22.14 ns (6.64 m)
3 · Why four satellites?
Each measurement is one equation. Drag the receiver, when four circles meet, you have enough to solve position and your clock bias at once.
Move the dot toward where all orange rings overlap.
4 · Regional constellation
NavIC uses GEO and IGSO slots over the Indian Ocean region so users see multiple satellites without a global 24‑sat GPS‑style grid.
Ready for live NavIC metrics? Open the status dashboard.