GPS Timestamps and Stale Location Data: How to Spot Old Readings
Learn why timestamps matter and how a page should distinguish a fresh location update from a cached position.
A location point without its age can be misleading. The browser's position object includes a timestamp that indicates when the location was obtained. A page may receive a cached point or stop receiving updates when the tab is hidden, so a displayed number can become old even while the screen remains on.
Freshness is part of quality
Accuracy tells you something about estimated position uncertainty; timestamp tells you when the point was produced. A recent point with poor accuracy may be unreliable, and an accurate-looking point from long ago may no longer describe the device's current position. Both factors should be considered together.
Why updates pause
Browsers can throttle background pages, the phone can enter a power-saving state, or the location provider may temporarily lose reception. The page may continue showing the last value unless it checks the timestamp and updates its status. Returning to the tab can trigger new updates, but not always instantly.
What a good interface should do
It should distinguish 'waiting for location', 'tracking', 'permission denied' and 'last update is old'. It should not present a stale speed as if it were live. If the website's display does not show update age, users should be cautious whenever the number appears frozen or does not react to known movement.
Safe troubleshooting
While stationary, stop and restart tracking using the interface, check permission and bring the page to the foreground. Avoid repeatedly starting new tracking sessions without stopping the old one, because duplicate watches can waste battery and confuse the display. If a session is important, test it before relying on it.
Frequently asked questions
Can a cached point be accurate but old?
Yes. Its location may have been good when captured but no longer represent the current position.
Why does the page stop updating when locked?
Mobile browsers and operating systems can limit background activity to save power.
Technical references
These references explain the underlying browser and positioning concepts. They do not imply endorsement of this website.