The short answer
Yes and no. GPS itself works without mobile signal: the phone receives satellite signals directly and can still work out where it is. What it can’t do without signal is send that position to anyone. A well-built tracking app stores positions while offline and uploads them once the phone reconnects, so the route is complete — just late.
GPS vs mobile data: two different things
GPS is receive-only: satellites broadcast, your phone listens. No SIM, no data, no mobile mast needed. Mobile data is what carries the position from the phone to a server and on to a map. Lose signal and you lose the second part, not the first.
Why the first fix can be slower without signal
Phones use the mobile network to speed up the first GPS fix (assisted GPS). Without it, the first position after the phone has been off or moved a long way can take longer. Once it has a fix, tracking works normally.
Does GPS tracking work without cell service in rural areas?
Rural dead spots are common across the UK, especially in hills and valleys. Positions are still recorded; they arrive in a burst when coverage returns. On a live map, the person appears to stop, then jumps along the route when they reconnect.
How TrackLink handles dead spots
TrackLink holds positions on the phone while it is offline and uploads them once it reconnects, so route history fills in — even after a long spell without signal. The live map shows how long ago each device was last heard from, so a gap is obvious rather than misleading.
If you need tracking with no signal at all
For remote areas with no coverage for long periods, satellite messengers can send positions via satellite rather than the mobile network. They are a different category of device, usually with their own subscription. See GPS tracking for hikers.
Common questions
Does GPS use mobile data?
Working out your position doesn't. Sending it to a map does, but only a tiny amount.
Will I lose tracking data in a dead spot?
Not with an app that stores positions offline. They upload when the phone reconnects.