User guide
The map shows where satellite navigation (GPS, Galileo, GLONASS, BeiDou) is disrupted. Aircraft act as the sensors: via ADS-B they broadcast their position together with how trustworthy that position is. When GNSS is jammed or spoofed, it shows in what they broadcast.
The panel at a glance
| Section | What it does |
|---|---|
| Layer | What the map shows: jamming, spoofing, both, or traffic |
| Time | Live, one hour, one day or a range of your choice, with a timeline; also the grid size, individual events and a shortcut to known regions |
| Interference in view | Figures for the part of the map you are looking at, with a list of the most affected cells or the largest spoofing cases |
| Settings | Colours and display, and the detection criteria in use |
The banner GPS jamming hotspots at the top leads to hourly statistics per region. The legend at the bottom right explains the colours and shows the period on the map.
Layers
| Layer | What you see |
|---|---|
| Jamming | Hexagonal cells, coloured by the share of aircraft that reported degraded GNSS there |
| Spoofing | Spoofing cases per aircraft (see Spoofing) |
| Both | Jamming cells with the spoofing cases drawn on top |
| Traffic | How many aircraft were seen per cell. Use it to judge coverage: an uncoloured area on the jamming layer can also simply mean that no aircraft were seen there. |
Jamming
How it is detected
With every position, an aircraft reports two quality values: the Navigation Integrity Category (NIC) — how far the true position can at most be from the reported one — and the Navigation Accuracy Category (NACp) — the expected error. A jammed receiver loses satellites and these values drop. An aircraft counts as affected in a cell when it reports a low value there; by default that is NIC below 7, meaning the position can no longer be guaranteed to within about 370 m.
What is left out
Not every low value is interference. By default the map ignores:
- aircraft that never report a good value (old or faulty avionics);
- aircraft on the ground or at low altitude, where take-off, landing and terrain disturb reception;
- low values long after the degradation began: a receiver needs time to recover after leaving a jammed area, and that recovery tail would otherwise colour cells far away. Only the first minutes after the onset count.
An aircraft whose position is being spoofed is not counted at its false position, so the location a spoofer pretends to be does not turn red itself.
Reading a cell
The colour is the percentage of affected aircraft among the aircraft with a known value. Cells with too few aircraft are not coloured, and one affected aircraft per cell is subtracted (the −1 correction) so that a single faulty transponder does not show up as interference. Click a cell for the figures behind it: the number of aircraft, how many were affected, spoofing indications, the distribution of the reported NIC values and an hourly trend for the surrounding days.
The grid follows the zoom level: coarse when zoomed out, finer when you zoom in; the finest cells are about 1,770 km². Grid under Time shows which one is in use. Over periods longer than an hour the counts add up per hour, so an aircraft that stays in a cell for three hours counts three times.
Spoofing
Spoofing makes a receiver compute a false position, while the reported quality often still looks fine. The monitor therefore looks at the position itself and compares it with information that does not come from GNSS. Indications are grouped per aircraft into cases.
| Method | What it looks for |
|---|---|
| Position jump | The position moves at an impossible speed and stays at the false location for a while |
| GNSS vs baro altitude | The GNSS altitude suddenly departs from the barometric altitude (which does not use GNSS) and stays off |
| Cluster | Several aircraft at very different altitudes report the same position at the same moment — typical of a spoofer's fixed location |
| Velocity vs position change | The reported speed does not match how the position actually moves, for example a position that stands still while the aircraft flies at 450 kt |
| MLAT vs GNSS | A position computed by ground receivers from the arrival times of the aircraft's signals — independent of GNSS — disagrees with the aircraft's own position |
| Heading, airspeed, vertical rate | The aircraft's own sensors disagree with GNSS. Wind and turns can cause this too, so these methods are weak on their own: by default they are only shown next to one of the methods above. |
Single glitches are filtered out: a false position or altitude offset has to persist for a while before it counts.
On the map
| Symbol | Meaning |
|---|---|
| Case with a position jump: from the last trustworthy position (green) to the false position (red) | |
| Case without a jump (altitude, cluster, velocity …); larger with more indications |
Click a case for the details: aircraft, period, offset and bearing, how long the false position was held and which methods were triggered. Tick Events under Time to see the individual indications as coloured dots; where the aircraft reported a different position, a thin line leads to it.
Time
- Live: the last 30 minutes to 2 hours, refreshed every minute (registered users).
- Hour and Day: step with ◀ ▶ or play through time with ⏵.
- Range: any period from–to. The length is limited; registered users can choose longer periods.
- The timeline shows how much data there is per hour or day; click a bar to go there. Purple bars come from the daily archives, the others from the live feed.
- The button next to Time switches between UTC and your local time.
- Go to jumps to a known region.
Visitors without an account see completed hours only, with a short delay.
Interference in view
For the visible part of the map this shows how many cells are severely or moderately affected and how many have enough data; on the spoofing layer, the number of cases, how many of them have a position jump and how many aircraft are involved. Open the list for the most affected cells or the largest cases, and click an entry to go there.
Settings
You can adjust the display: a colour scale or three classes (none / moderate / severe), the palette and its bounds, the opacity, and whether cells without interference or with too little data are shown. Your choices are remembered in your browser; Defaults restores them. The detection criteria themselves — thresholds and filters — are set by the administrator; Detection criteria at the bottom of the Display tab lists the ones currently in use.
On a smartphone
The map fills the screen. Tap the small GNSSRFI ☰ logo at the top left to open or close the menu, tap a section header to expand it, and tap the legend to expand it.
Hotspot pages
GPS jamming hotspots gives hourly updated statistics for regions such as the Baltic Sea, the Black Sea and the Eastern Mediterranean: the status over the last 24 hours, a map of the last 7 days, the daily trend over 30 days and the number of aircraft with spoofing indications. The figures are counted in area-hours: one cell during one hour. An area-hour counts as affected when the share of affected aircraft in it exceeds the threshold.
Accounts and live data
With an account you can also see live data and select longer ranges. Choose Log in → Request an account; you need a PIN code from the administrator, who then approves the account.
Limitations
- All indicators are heuristic. A coloured cell shows where aircraft experienced degraded GNSS; it does not identify a transmitter or prove intent.
- Aircraft at cruising altitude see a jammer from hundreds of kilometres away, so an affected area is usually much larger than the surroundings of the transmitter itself.
- Coverage depends on volunteer receivers and on traffic: over sea, in remote areas and at night there are fewer aircraft and therefore fewer observations.
- Faulty avionics, receiver start-up and reception problems can look like interference. Look at the number of aircraft in a cell and at whether the pattern persists.
- Spoofing detection is experimental: it can produce false alarms as well as miss cases. Some indications (clusters, GPS-loss flags from receivers) only come from live data and are missing for periods without it.
More background: about the map · regional statistics: GPS jamming hotspots.