GNSS-Denied USV Navigation

A survey line is only as good as the position under it. GNSS on a small USV fails in exactly the places survey work happens: under bridges and along quay walls where the sky is blocked, next to offshore structures that shadow and reflect the signal, and in ports where radio interference is routine. When the fix drops, a standard autopilot drifts off the line or stops, and the data from that stretch is lost.

This bundle keeps the boat positioned through the outage. It combines three sensors with a software layer that decides which of them to trust, and it plugs into a USV already running ArduPilot.

The bundle contains:

• Anti-jam GNSS antenna that rejects interference arriving from low elevations; a multi-element CRPA antenna in the Pro tier
• Inertial navigation unit (INS) that carries position and heading through the gap
• DVL (Doppler velocity log) that measures speed over the seabed, so dead reckoning stays accurate for far longer than inertial alone
• GNSS spoofing detection with automatic source switching: our software checks the GNSS fix against the inertial and DVL solution and, when they disagree, switches the autopilot to the non-GNSS sources, then back once GNSS is trustworthy again
• ArduPilot integration: drivers, parameters and a documented configuration for ArduPilot Rover in boat mode (surface vessels) and ArduSub (ROVs and AUVs), built on ArduPilot’s supported External AHRS drivers, plus our GNSS integrity monitor that detects jamming and spoofing and switches navigation to the INS and DVL

Optional:

• Coastal position fix: radar or camera matched to the shoreline, giving an independent position fix that limits drift on long outages

Bundle Tiers

The coastal position fix can be added to either tier.

Every configuration is quoted for the boat it goes on. Higher-accuracy DVL and inertial variants and multi-element CRPA antennas are commonly export-controlled, so those configurations are quoted on request and subject to export licensing. Product names identify the class of component; Subsea Formula is independent of their manufacturers.

Limitations

• DVL bottom-lock needs the seabed within range, which means shallow and coastal water. In deep water the DVL falls back to water-track, and drift then depends on the grade of the INS.
• The entry tier is built for coastal and inshore survey. For long outages in open water, choose the Pro tier’s FOG-grade INS, the coastal position fix, or both.
• Spoofing detection isolates a bad fix but does not restore GNSS. During an outage, position accuracy is limited by the INS and DVL solution.
• Each bundle is configured for the specific hull and mission: sensor mounting, lever arms and parameters are set for the boat it goes on.