Position & track
Sky plot
Signal strength (C/N₀)
Constellations in view
Receiver health & integrity
Speed over time
Altitude over time
Vertical speed over time
Accuracy over time
Trip statistics
How this works
What am I looking at?
A GNSS receiver (this one is a u-blox NEO-M9N) listens to radio signals from navigation satellites orbiting ~20,000 km up. By measuring how long each signal takes to arrive, it works out its own position, altitude, speed and heading, then streams that to this site over WiFi.
The four constellations
GPS (USA), GLONASS (Russia), Galileo (EU) and BeiDou (China) are independent satellite systems. A multi-constellation receiver uses all of them at once, so it sees more satellites and gets a faster, more reliable fix — especially among buildings or trees.
Sky plot & signal strength
The sky plot shows where each satellite is in the sky: the centre is straight overhead (zenith), the edge is the horizon, and the angle around the circle is the compass bearing. Colour shows signal strength (C/N₀ in dB-Hz) — green is strong, red is weak. Satellites spread evenly across the sky give the most accurate fix.
What is HDOP / accuracy?
HDOP (Horizontal Dilution of Precision) describes how favourable the satellite geometry is. Lower is better: under 1 is ideal, 1–2 excellent, 2–5 good. A low HDOP with many satellites means the position is trustworthy to within a few metres.
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