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AIS Position Validation for Enhanced Maritime Domain Awareness

Spire Global's Doppler Geolocation Validation (DGV) API and proprietary cube satellite constellation help validate vessel position for thousands of ships using AIS in near-real-time.

Doppler Geolocation Validation for More Complete Maritime Domain Awareness

Spire Global, an industry-leading space-to-cloud data and analytics company that specializes in maritime domain awareness, uses its new Doppler Geolocation Validation (DGV) API and proprietary cube satellite constellation to validate ship position integrity for thousands of vessels across the globe.

The DGV service independently provides accurate estimates of a vessel's position at the time of an AIS transmission using "doppler data" or "RF emissions" emitted by a ship in transit. Once paired alongside an AIS track, authorities can better identify an instance of AIS spoofing or manipulation if the AIS position significantly varies from the doppler data.

Spire AIS Position Validation

Spire Global's GVD API identifies and reports the following validation events:


If a vessel’s AIS transceiver loses its input GNSS connection (either via a malfunction or by deliberate removal), then the default behavior of most AIS transceivers is to continue to transmit position reports, but with the position set to an 'illogical/impossible', '181/91' longitude/latitude.

However, since Spire can calculate the position of a vessel independently from its position report content, they are able to flag those vessels as reporting ‘181/91’ events while also providing the estimated location of the vessel - even if it is effectively ‘dark’ from an AIS point of view.

Out of Footprint

The receiving footprint of the Earth’s surface for Spire Global's satellite-mounted AIS receiver payloads is typically around 5,000 km in diameter. If Spire calculates a vessel's estimated position to be outside of the receiving satellite’s footprint, but the vessel’s AIS position is tracked inside of the receiving satellite’s footprint, Spire can flag those vessels as reporting ‘Out of Footprint.'

This gives maritime authorities a more detailed look at how ships operate under the radar, and allows them to better prepare for similar events in the future.


If a sequence of AIS messages reports a stationary position for a vessel, but Spire's estimated positions indicate that a vessel is actually in transit, they will flag those vessels as reporting ‘Fixed’ events. Fixed events are an easy way to invalidate or validate the AIS position of a vessel.

Case-Study: Verified by a Leading OSINT Firm (Geollect)

“With the SYMPHONY 3 (IMO 9288083), Geollect identified several transits where the ship was almost certainly manipulating its AIS positions. The manipulated positions placed the ship near West Africa. However, DGV data from Spire identified transmissions suggesting that the SYMPHONY 3 was heading to Venezuela. As multiple transmissions were located close to Port Jose Terminal, Geollect utilized satellite imagery of the terminal and identified a vessel assessed to almost certainly be the SYMPHONY 3 alongside in early August.” — Geollect

For a closer look at this AIS position validation study, you can navigate the extended report HERE.

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