What does the “GPS signal is unreliable” warning mean?

Question

Accepted Answer

The app detected that satellite data contradicts itself and shows the last confirmed point instead of the suspicious one. This is protection against someone else's fake GPS signal, not an app error.

The app checks every coordinate against several independent signs: a physically possible speed of movement, altitude and how fast it changes, agreement with ground sources — cell towers and Wi-Fi networks, which cannot be faked by the same transmitter as the satellite signal.

The reason for this check was a real case: in three and a half seconds the marker “moved” fifty kilometers, while the altitude grew at a constant eight meters per second — a picture impossible for a person walking. Ground sources at the same moment were never off by more than a couple of kilometers.

What to do: as a rule, nothing — the warning disappears by itself when the signal becomes consistent, and the app tells you so separately. If it persists for a long time in the same place, most often there is a source of interference nearby, or the phone is somewhere satellites are poorly visible and the network gives contradictory data. The warning does not affect spoofing itself: it concerns only determining your real location.