Interference: some → strong
Likely jammer (estimate)
Ship, nothing odd
Official warning area
Ground station
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Where satellite positioning is being jammed or spoofed, worked out live from aircraft and ships reporting the health of their own GPS, beside the official warnings.
Under development: the methods and the coverage are still growing. Treat everything here as experimental, and as a pointer to watch your own receiver, not a verdict.
Airliners broadcast their position every second, with a figure for how much they trust their own GPS (NACp and NIC). When many aircraft in one area report that they have lost it, something there is jamming. The receivers also note where each aircraft last had good GPS, which traces the edge of the jammed area.
Ships report their position by AIS. A spoofed ship gives itself away: it appears far inland, jumps faster than any ship can sail, or lands on exactly the same spot as other ships. Live for the Baltic for now, where it is worst; the jump check builds up while the page is open.
A jammer on the ground reaches much further up than along the sea: an aircraft at 35,000 ft sees it from about 400 km, a ship's antenna from roughly 40 km. Where the aircraft outline a jammed area, the page estimates the source and draws its likely reach at sea level.
Public signals only: what aircraft and ships broadcast about their own positions, and the official navigational warnings.
Not proof of who is doing it, and not complete: aircraft only see where aircraft fly and receivers listen, and the ship check covers the Baltic for now. The reach at sea is an estimate from geometry, not a measurement. Watch your own receiver and use the official broadcast at sea.
Every position, heading and clock offshore leans on satellites. Jamming takes them away; spoofing is worse, because the position looks fine and is wrong. Pair it with Space Weather for the sky itself.