A jumpy, inflated, or just plain wrong GPS speed reading is almost never a "broken app" problem — it's usually one of a handful of well-understood, fixable causes. Here's what actually moves the needle, in order of impact.
1. Get a clear view of the sky
GPS accuracy depends entirely on how many satellites your device can see and how well-spread they are across the sky. Tall buildings, dense tree cover, parking garages, and being indoors all block or weaken those signals. If you're testing speed indoors or in a dense urban canyon, expect a noisier, less reliable reading no matter how good your device is — this one's physics, not software.
2. Give it a few seconds to lock on
The very first fix after granting location permission is typically the least accurate one your device will produce. GPS chips refine their position estimate as they gather more satellite signal over the first several seconds. Glancing at the speed reading the instant tracking starts is the single most common reason people see an oddly high or low first number — wait a few seconds for the reading to settle before trusting it.
3. Keep the phone steady, or mount it
Handheld phones bounce, tilt, and rotate, which doesn't change your GPS position much directly but does make it harder for the chip to maintain a stable signal lock, especially indoors or near reflective surfaces. If you're checking speed in a vehicle, a simple windshield or dashboard mount with a clear sky view will consistently outperform a phone shifting around in a cup holder or pocket.
4. Watch the accuracy indicator, not just the speed
Most GPS APIs (including the one this site uses) report an accuracy radius alongside each position — essentially "we're confident you're within this many meters of this point." A ±5m accuracy reading is trustworthy; a ±50m or higher reading means the underlying position is uncertain enough that any speed calculated from it should be treated with real skepticism. Our own speedometer surfaces this directly: if your accuracy radius gets too wide, you'll see a note telling you so, rather than a confident-looking number hiding shaky data underneath.
5. Remember that slow speeds amplify error
GPS position uncertainty is roughly constant in absolute terms — a few meters, regardless of how fast you're moving. But speed is distance divided by time, so that same few meters of uncertainty is a rounding error at highway speed and a huge relative error at walking pace. A few meters of GPS "drift" between readings can look identical to someone actually walking, which is why good speed-tracking tools apply a noise floor — treating movement smaller than the GPS's own uncertainty as standing still rather than real motion — instead of reporting every fluctuation as speed.
6. Turn off battery saver / low power mode while tracking
Power-saving modes on both iOS and Android commonly throttle how often apps can request a fresh GPS fix, trading accuracy and update frequency for battery life. If you're specifically trying to get a precise, responsive speed reading, temporarily disabling low power mode will usually give the GPS chip permission to update more often and more precisely.
7. Keep your OS and browser updated
Both operating systems and browsers periodically improve their location stack — better satellite constellation support (including non-GPS systems like Galileo and GLONASS, which modern chips blend with GPS for better fixes), better filtering, better power management. Running an outdated OS or browser version occasionally means missing out on real accuracy improvements at no cost to you.
Putting it together
None of these are exotic fixes — clear sky view, a few seconds of patience, a steady mount, and paying attention to the accuracy figure will solve the vast majority of "my GPS speed looks wrong" situations. For the deeper why behind GPS error sources, see our piece on how GPS actually calculates speed.