Who the map is for

What the map measures

Every hexagon counts the aircraft that crossed it in the previous UTC day and the share that reported a degraded position. Aircraft make the measurement because they broadcast their position accuracy and fly almost everywhere. That matters for everyone else in two ways. An aircraft at 35,000 feet can pick up a jammer hundreds of kilometres away that a receiver on the ground, behind hills and the curve of the Earth, would never hear. And a small jammer in a car or on a roof can wreck reception for a few hundred metres at street level and never reach the aircraft above. So the map shows where interference has been routine. It can't say whether your receiver, at your height, will lose its fix today.

Pilots and dispatchers

For a crew it's background, not a briefing: which regions have had GNSS problems for months, how yesterday compared, and the altitude layers where the loss sits. The "By altitude" table on a region page splits each count into low, mid and high layers. Loss confined to the high layers usually means a distant, powerful transmitter, while loss in the low layers near an airport points to something close to the ground. Operational decisions rest on NOTAMs, the AIP, the operator's procedures and the aircraft's own indications. EASA and IATA's joint plan and the FAA's guidance to pilots are summarised, with sources, on the About page.

Drone operators

A drone flies low, so the low layer of a region page is the closest guide. Interference in a region is a reason to plan for the drone losing GPS: hold-position and return-to-home both depend on it, and a spoofed drone can drift while its screen says it's still. Keep it in sight, know how it behaves without satellites, and follow the national aviation authority's rules for the area. The map can't clear a site; a quiet hexagon only means aircraft crossing it yesterday had no trouble.

Sailors and mariners

Several of the most affected regions are seas: the Baltic, the Black Sea, the Eastern Mediterranean and the Persian Gulf, covered on the Middle East page. A ship's GNSS and the AIS positions built on it can be jammed or spoofed in the same areas. The map is a passage-planning check, alongside navigational warnings, notices to mariners and a plotter cross-checked against radar, depth and visual bearings.

Drivers, cyclists and hikers

On the ground, interference is patchier than the hexagons suggest, because hills and buildings block distant transmitters while nearby ones matter more. In the affected regions, and especially near borders and military areas, it is worth carrying an offline map, knowing the route, and not relying on a phone or watch alone for a position in the hills or at sea. Phones often hold their place for a while from mobile masts and Wi-Fi, so a jammed phone may look fine in town and lose its place out of reach of both.

What it is not

It isn't current: the map is rebuilt once a day from the previous UTC day, so it says nothing about the next hour, and interference moves as exercises end and transmitters switch on and off. It doesn't say which satellite system was affected, or whether a receiver was jammed or spoofed. And it never replaces official warnings for aviation, shipping or drones. The how to read page goes through the colours, the blank areas and the common misreadings; the regions index lists every region and country page.

Anyone building a tool for any of these users can get the same hexagons as JSON for any saved day from the API, open under the Open Database License with attribution to GPSInterference.com and adsb.lol.