Created by Harry Ellis
GNSS Live monitors electromagnetic anomalies in the world's most strategically important maritime chokepoints using NASA's CYGNSS satellite constellation. When military radar, electronic warfare systems, or unusual vessel activity disturbs the RF environment over the ocean surface, CYGNSS detects it.
The platform provides free, open-access passive satellite intelligence derived entirely from publicly available NASA CYGNSS data. All data is subject to approximately 6 days of NASA processing latency before becoming available here. No classified sources, no proprietary sensors, no charges.
Most publicly available GPS interference monitoring relies on aircraft. Services like GPSJam aggregate reports from commercial flights - when a plane's GPS is disrupted, that disruption gets logged and mapped. This works well over land and busy air corridors, but has a fundamental gap: aircraft don't fly over open ocean, conflict zones, or remote maritime chokepoints.
GNSS Live uses a different approach entirely. Rather than waiting for a receiver to report disruption, it uses NASA's CYGNSS satellites to passively measure the electromagnetic environment at the ocean surface. CYGNSS orbits the Earth continuously between 38 degrees north and south, covering the Red Sea, Strait of Hormuz, South China Sea, Taiwan Strait, and other strategically critical waters that aircraft-based monitoring cannot reach.
To our knowledge, this is the first publicly accessible platform to provide continuous passive RF anomaly monitoring over open ocean chokepoints using satellite reflectometry. The methodology draws on published research in GPS jammer localisation from space, applying it to a global maritime intelligence context for the first time.
Anomaly spikes have been independently validated against confirmed Houthi attack events across the October 2023 - October 2025 campaign period.
| Date | Event | Match |
|---|---|---|
| 27 Nov 2023 | Missiles at USS Mason | Confirmed |
| 13 Dec 2023 | Ardmore Encounter attack | Confirmed |
| 15 Dec 2023 | Maersk suspends ops | Confirmed |
| 01 Jan 2024 | Iranian warship Alborz | Confirmed |
| 16 Jan 2024 | Post-Poseidon Archer | Confirmed |
| 19 Feb 2026 | Houthi mobilisation | Confirmed |
CYGNSS Level 2 Science Data Record V3.2, sourced from NASA PO.DAAC under Creative Commons Zero licence. Each daily file contains all eight satellite observations merged into a single NetCDF file (~150MB). Data is subject to approximately 6 days of NASA processing latency - observations from today will appear here in roughly 6 days. This is a characteristic of the CYGNSS L2 product and not something that can be changed. All data on this platform is free and open to access with no registration required.
The Normalised Bistatic Radar Cross Section (NBRCS) measures GPS signal reflectivity from the ocean surface. Elevated NBRCS relative to a 24-hour rolling baseline indicates unusual electromagnetic conditions - consistent with military radar, electronic warfare systems, or abnormal vessel traffic.
A rolling z-score is computed per hour against a 24-hour window. Events exceeding z > 1.5 are flagged as anomalies.
Inspired by Gorman (GPS World, May 2026), a second detection channel uses cross-channel NBRCS variance - the standard deviation of NBRCS readings across the five DDM channels within each observation. When a jammer is active, channels disagree significantly, elevating this variance independently of the mean signal level.
Events where both channels fire simultaneously are flagged as dual-signal - the highest confidence detection tier.
For significant events, a parametric inverse-distance model is fitted to the spatial pattern of anomalous CYGNSS observations. The underlying physics is simple: signal power from a RF source falls off with the square of distance. By finding the point that best explains the observed pattern of elevated readings across multiple satellite passes, a source position can be estimated.
The location radius shown on the map is the CEP - circular error probable. This is the radius within which the true source location falls 50% of the time, estimated by running the localisation 200 times on randomised subsets of the observations and measuring how much the result moves. A tight CEP means the observations strongly agree on a single source location. A wide CEP means the observations are spread or sparse and the estimate is uncertain. It is not a guarantee of accuracy - it reflects the consistency of the satellite data on that day.
The localisation approach is based on work by Gorman (GPS World, May 2026), which demonstrated sub-5km jammer localisation using CYGNSS over the Strait of Hormuz. GNSS Live applies the same framework across all monitored zones using L2 data.
L1 reactive download is triggered for events above z > 2.5, enabling four-method detection (noise floor, spatial grid, SNR hole, NBRCS drop) and sub-20km localisation accuracy.
CYGNSS covers latitudes 38°N to 38°S. Coverage above 38°N (Ukraine, Baltic, Nordic) is not available from this data source. Localisation accuracy varies from <15km on clean single-source days to >100km on multi-source or low-observation days. All classifications are probabilistic estimates, not confirmed attributions.
All endpoints return JSON. Authenticate with your API key in the request header.
All data is freely available and open access. No registration or API key required for the data shown on this map.