Why your GPS speedometer shows 0
Short answer: a phone speedometer measures speed from GPS satellites. When the phone cannot see the sky (inside a train car, in a tunnel, under a metal roof or indoors) it has no fix and shows 0, even though you are moving. Move next to a window and wait a few seconds.
Why it happens
Your phone has no wheel sensor. It works out speed from how its GPS position changes over time. Metal and concrete block satellite signals, so a train car, bus, tunnel or parking garage can cut the signal completely. Reviewers describe it as the app that "stops working even though still moving" or "literally says zero".
On a train
People love checking the speed of a bullet train, SRT or KTX. Sit by the window and hold the phone close to the glass. Tinted or metal-coated windows weaken the signal, so give it 10 to 30 seconds to lock on. Set the dial range high enough (300) so the needle does not hit the end.
Other fixes
- Allow precise location, not approximate.
- Turn off battery saver for the app so GPS is not throttled.
- Keep the screen on while measuring; Gaugely has a keep-screen-on option.
- After a tunnel, expect a few seconds of delay while GPS settles.
What 0 does not mean
A 0 with no signal is not a broken app. Gaugely works offline from GPS alone, and trips keep the distance recorded before and after the gap.
FAQ
Why does my speedometer app literally say zero?
It has no GPS fix. The phone needs to see satellites, and metal roofs, tunnels and buildings block them.
Does a GPS speedometer work on a bullet train?
Yes, usually from a window seat. Train cars are metal boxes, so the aisle side often loses the signal.
Why is the speed delayed?
GPS updates about once a second and needs a few readings to settle, so expect a short lag after a stop or a tunnel.