What does this map actually show?

It shows the share of aircraft in each hexagon whose own broadcasts reported degraded navigation accuracy, specifically NIC below 7 or NACp below 8. It does not detect a jammer, locate a transmitter, or attribute a cause.

What are NIC and NACp?

They are integrity and accuracy fields an aircraft transmits with its position. NIC describes the containment radius the position is claimed to sit within, and NACp describes the 95 percent accuracy of that position. When GNSS reception is degraded, a correctly working transponder lowers these numbers, which is what this map counts.

Why is the map empty in some regions?

AeroScope only holds data where volunteer ADS-B receivers cover, and it only fetches the areas its own visitors are looking at. Empty space means no observations, not clear skies.

Can degraded accuracy have innocent causes?

Yes. Older avionics, poor satellite geometry, multipath near terrain and uncertified installations all lower these fields. That is why single aircraft never color a cell and why cells need at least eight distinct aircraft before they appear.

LIVE, FROM AIRCRAFT REPORTS

GPS jamming and GNSS interference map

Aircraft broadcast how good they believe their own position is. When that confidence collapses across many aircraft in the same place, something is interfering with GNSS reception. This map counts exactly that, and nothing more.

Method

How the number in each hexagon is produced

Every ADS-B position carries two self-reported quality fields. NIC states the containment radius the aircraft claims its position falls within. NACp states the 95 percent accuracy of that position. A correctly working transponder lowers both when its GNSS receiver struggles, so a sudden collapse across many unrelated aircraft in one area is the visible fingerprint of interference. See NIC and NACp explained for the full value scale.

An aircraft counts as degraded when NIC is below 7 or NACp is below 8. Each hexagon is an H3 resolution 4 cell, roughly 22 km across. Aircraft are counted once per cell per hour, and a cell is only drawn once at least 8 distinct aircraft have crossed it, so a single unusual aircraft cannot color the map.

What is deliberately excluded

ADS-B version 0 transmitters, which report these fields as zero by design
Positions that are not the aircraft's own broadcast: multilateration, TIS-B and ADS-R
Gliders, ultralights and UAVs, whose converters frequently have no GNSS source at all
Installations reporting SIL 0, meaning an uncertified or unknown position source. In live data these were nearly every false positive we saw, light aircraft reporting zeros in clear skies

Limits

What this map cannot tell you

It does not detect a jammer. It measures the effect on receivers, not the transmitter. Nothing here locates or attributes a source.
Degradation has innocent causes. Older avionics, satellite geometry and multipath near terrain all lower these fields.
Empty is not clear. Blank areas mean no observations. Coverage follows volunteer ADS-B receivers, and AeroScope fetches the areas its own visitors are viewing, so large parts of the world are simply unobserved here.
Spoofing is a different problem. A convincing spoof can keep these fields high while reporting a false position. See spoofing detection for the checks that target that case.

This is the same honest framing used on the limitations page, and it applies here too: a surveillance signal whose limits you do not know is worse than one whose limits you do.

Questions

Common questions

Is this the same as gpsjam.org?

It uses the same underlying idea, aircraft-reported navigation accuracy, and both are honest that the measure is indirect. The differences are that this map updates continuously rather than once a day, it excludes SIL 0 installations to cut false positives, and its coverage is smaller because AeroScope is a much smaller observer.

How often does it update?

Cells are recounted continuously and this page reads the last 6, 24 or 72 hours on request. Completed hours are kept for 7 days.

Can I get this as data?

Yes, the same figures come from a public endpoint, /api/overlays/gnss?hours=24, which returns each cell with its counts and boundary. See the API docs.

Does a red cell mean my flight is unsafe?

No. Aircraft carry multiple navigation sources and crews are trained for GNSS loss. This map is an observation tool, not a safety product, and must never be used for navigation or air traffic control.