Plain-English guide
How Does a GPS Speedometer Work?
A GPS speedometer measures speed from satellite signals — either directly from Doppler shift or by dividing distance between fixes by time. Speed can be more accurate than position.
This Easy-difficulty question cluster (“how does a gps speedometer work”, “how accurate is gps speedometer”) lives here. Plain-language explanation of GPS trilateration, why speed can be more accurate than position, typical accuracy ranges, and factors that degrade it (tunnels, dense urban canyons, indoor use). Includes a live tool so the page is not thin.
Tap Start to measure your speed. Your browser will ask for location permission — coordinates are processed locally and never sent anywhere.
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Off by default. Only active while tracking — we never keep your screen on otherwise.
Try the live speedometer above while you read — it uses the same engine described below.
Coordinates never leave your device — Learn how GPS speed is measured →
Trilateration in 30 seconds
Your phone listens to at least 4 satellites, each stamping time from atomic clocks. By comparing arrival times, it solves its position. Do that repeatedly and you get movement.
Why speed can beat position
Position needs absolute accuracy; speed can use Doppler shift of the carrier wave and short-baseline distance. Even if your dot is 5m off, the change over a second can still give speed within ~1 km/h outdoors.
Typical accuracy
Open sky: ±1–3 km/h at steady speed, ±3–5m position. Light urban: ±3–5 km/h, weak signal. Tunnels/indoor: no fix or weak — we show Searching, not a fake number.
What degrades it
Tunnels (no view), dense urban canyons (reflections), indoors, heavy tree cover, and holding the phone in a pocket (antenna blocked). Move near a window or outdoors, hold steady, check the ±m badge.
Privacy-first — coordinates never leave your device
Processed locally in your browser, never stored on a server. Close the tab and it's gone. Learn how GPS speed is measured →
Frequently asked
Page-specific questions — same data drives the FAQ schema below.
How does GPS calculate speed?
With at least four satellites your phone solves its position by trilateration. Speed comes from Doppler shift on the signal or from distance between fixes divided by time — plain math, not guesswork.
Why is my GPS speed reading inaccurate?
Usually because the signal is blocked or reflected — in tunnels, between tall buildings, indoors, or before the first fix warms up. Move near a window or outdoors and wait 20–30 seconds.
Is GPS speed the same as my phone's built-in speedometer app?
Usually yes — most phone speedometer apps use the same underlying browser or OS Geolocation API. This page just shows it in your browser without installing anything.
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