Why GPS Speed Fails in Tunnels and Indoors

GPS speed can disappear in a tunnel or building because the receiver cannot obtain enough usable satellite signals. Changing speed units or repeatedly refreshing the page cannot remove that physical obstruction.

Blocked and reflected signals

Roofs, walls and terrain can block signals; nearby structures can also reflect them. The result may be a missing reading, a jumping position or a delayed update. A street between tall buildings can be difficult even though you are outdoors.

Network location may still place you near a building without providing useful speed. Location availability and speed availability are separate: the browser can return coordinates with no speed value.

What a missing reading means

A zero, frozen value or unavailable message does not prove that a vehicle has stopped. Some software retains the last reading; other software displays zero when a speed field is missing. In the SpeedX web speedometer, missing speed can initially appear as zero before signal warnings are shown. Read the status alongside the number.

Check recovery

1. Wait until you can safely reach an open area.
2. Keep location permission enabled and allow new readings to arrive.
3. Check both position updates and speed during a short walk.
4. If data still fails outdoors, use the troubleshooting guide below.

Can an app fill the gap?

Some navigation systems estimate motion with other sensors, but that does not guarantee this tool does so. Do not assume continuous measured speed through a tunnel. For trip analysis, a gap in satellite reception should be treated as uncertainty rather than proof of constant speed.

Try it and keep reading

• GPS coordinates
• Fix missing GPS speed readings

References

• GPS.gov: GPS Accuracy
• MDN: GeolocationCoordinates.speed