Live Tutorials
GNSS Satellite Behaviour
Real data from your live GNSS receiver — 48-hour rolling history of elevation, azimuth, visibility and signal strength, updated every minute.
Elevation vs Time
Sinusoidal rise → peak → set cycle — degrees above horizon
Why is elevation sinusoidal?
GNSS satellites orbit at ~20,000 km in medium Earth orbit, completing one revolution every ~12 hours. As the Earth rotates beneath them, each satellite appears to rise from the horizon, reach a peak elevation, then set again — tracing a smooth sine-like arc. Over 48 hours you will see ~4 full cycles. Higher elevation = shorter signal path through the atmosphere = better position accuracy. Satellites below ~10° are typically masked out by receivers because tropospheric and ionospheric errors become too large.
Azimuth vs Time
Directional bearing 0°–360° (North = 0°)
Why does azimuth wrap around 360°?
Azimuth is the compass bearing from your receiver to the satellite. As the satellite sweeps across the sky it passes through all compass directions continuously. When the value reaches 360° it wraps back to 0° — this is not an error, it is simply the satellite crossing the North line. GPS satellites orbit roughly West-to-East from mid-latitude observers, giving each satellite a characteristic sweep direction.
Visibility / Receiver Lock
1 = receiver has a lock, 0 = no lock
Why does visibility follow a repeating on/off pattern?
A receiver can only track a satellite while it is above the local horizon. Each 12-hour orbit gives roughly 6 hours visible + 6 hours below horizon per cycle. The binary step chart mirrors the elevation curve: the satellite drops below the cut-off mask angle, the receiver loses lock (0), then it rises again and lock is re-acquired (1). In urban environments buildings can cause additional short-term outages.
Signal Strength — C/N₀
Carrier-to-noise density ratio in dB-Hz — higher is better
Why does signal strength track elevation?
C/N₀ (carrier-to-noise density, dB-Hz) is the key quality indicator reported by every GNSS receiver. When a satellite is low on the horizon its signal travels through more atmosphere, causing higher tropospheric delay, increased multipath reflections off nearby surfaces, and elevated thermal noise. As elevation rises the path shortens and C/N₀ improves. Below ~35 dB-Hz measurements are unreliable. Above 45 dB-Hz is excellent and suitable for high-precision RTK. This curve is one of the most important diagnostics when evaluating a GNSS installation site.