§01What questions does this template answer?
- Where did aircraft report degraded GNSS navigation yesterday, and how does that compare with the last four weeks?
- Which areas are newly affected this week?
- How many flights crossed a degraded area, and at which altitudes?
- Is today's pattern consistent with official advisories for the region?
Scroll sideways to see the full diagram.
§02How does the interference map work?
NIC defines a containment radius around each reported position, from under 7.5 m at NIC 11 to unknown at NIC 0; NACp is a 95% accuracy bound1Source 1 · Junzi Sun, TU Delft (mode-s.org)The 1090 Megahertz Riddle: Uncertainty, accuracy and integritymode-s.org. US rules require NIC 7 or better (under 0.2 NM) in normal operation, and research groups use lower values as a proxy for degraded GNSS reception2Source 2 · Liu, Lo, Blanch, Chen, Walter — NAVIGATION (Institute of Navigation), vol. 72 no. 3, 2025Locating GNSS interference sources using ADS-B with non-linear least squaresnavi.ion.org. The template classifies each aircraft by its median NIC in a cell, then computes the degraded share with the minus-one correction popularized by GPSJam, whose public map classifies aircraft on NACp and uses 2% and 10% as the boundaries between low, medium and high3Source 3 · GPSJam.orgGPSJam FAQgpsjam.org. NACp can be selected as the classifier instead of NIC.
Degraded share=max(degraded aircraft − 1, 0) ÷ total aircraft
- degraded aircraft
- Distinct aircraft with median NIC < 7 in the cell that day
- total aircraft
- Distinct aircraft with at least one airborne report in the cell
| Parameter | Default | Why |
|---|---|---|
| Degraded threshold | median NIC < 7 | Below the normal-operation requirement |
| Cell size | H3 resolution 4 | Enough aircraft per cell for stable shares |
| Minimum traffic | 5 distinct aircraft | Hide cells too sparse to judge |
| Bands | < 2%, 2–10%, > 10% | Consistent with public practice |
| Alert | > 10% and > 3× baseline, 2 days | Change, not chronic noise |
§03Which dashboards are included?
- Daily map: hexagons colored by band, with "insufficient traffic" shown in neutral gray, never green.
- New and changed areas: cells whose share rose above baseline in the last 7 days.
- Area drill-down: degraded share over time, aircraft count, altitude distribution and a list of (simulated in preview) flights that crossed the cell.
- Data health: share of reports with quality fields, receiver uptime, chronic-offender airframes excluded.
§04How do I adapt it to my region?
Busy regions can use finer cells (resolution 5) without losing stability; sparse regions should stay coarse or raise the minimum traffic count. If a few airframes report low integrity everywhere they fly, add them to the chronic-offender list rather than raising the threshold for everyone.
Background reading: Mapping GNSS interference with ADS-B quality indicators and the Airspace Awareness from Open Data whitepaper. The map layer appears on Map and alongside tracks in Airspace.
Frequently asked questions
Can I use OpenSky alone for this template?
Why median NIC per aircraft instead of every report?
Does a red cell mean there is a jammer in that cell?
How often does the map update?
Sources
4 references- The 1090 Megahertz Riddle: Uncertainty, accuracy and integrity (opens in a new tab)Junzi Sun, TU Delft (mode-s.org)mode-s.org
- Locating GNSS interference sources using ADS-B with non-linear least squares (opens in a new tab)Liu, Lo, Blanch, Chen, Walter — NAVIGATION (Institute of Navigation), vol. 72 no. 32025navi.ion.org
NIC as GNSS reception proxy; NIC ≥ 7 requirement.
- GPSJam FAQ (opens in a new tab)GPSJam.orggpsjam.org
Daily hexagon aggregation, thresholds, minus-one correction.
- EASA updates Safety Information Bulletin on global navigation satellite system outages and alterations (opens in a new tab)EASA2024easa.europa.eu
External sources were accessed at the time of writing. Kimo product details, customers and figures in examples are illustrative unless a source is cited.
