Dynamic Positioning

DP Mini Guide: GNSS — Jamming and Spoofing

🕑 9 min read 1350 words Dp-academy

Crew Connect DP Academy · Mini Guide 04

GNSS — Jamming and Spoofing

Topic: Position Reference Systems · Sub-topic: GNSS/DGNSS · Level: DPO / Senior DPO · Read time: 9 min

Training scenario only. In an actual operation, follow the approved vessel- and activity-specific procedures, ASOG/CAM/TAM, FMEA and emergency response arrangements; apply the Master’s authority and escalate through the applicable command structure. This guide is Crew Connect educational content — it does not override your vessel’s approved documents.

1. What / Why / How

GNSS position depends on satellite signals and, usually, differential correction data. Jamming/denial means loss or degradation of signal; spoofing means plausible-looking but false position data being received instead. They look and behave differently, and call for different reasoning.

2. Recognition / Risk / But

Watch for: simultaneous loss of same-principle sources, loss of corrections, abnormal quality indicators, inconsistent speed/position, or a mismatch against an independent (non-GNSS) PRS.

But: onboard equipment faults, an antenna change, shielding or reflection, and ordinary environmental effects can all resemble external interference. Don't reach for "jamming" as the explanation before ruling out the vessel's own systems.

3. Now / What next / Decision / Why

Validate using genuinely independent-principle sources and vessel checks. Identify which of your references actually share the suspected failure path (usually: anything GNSS-based). Apply your approved response/reporting procedure and any resulting operational limits.

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