Executive Summary
Norwegian war-risk mutual DNK is offering members a premium rebate for fitting assured PNT equipment built on Iridium's low-Earth-orbit network to counter GNSS interference. LEO-based PNT is a timing-and-integrity backup and a means of bounding inertial drift during GNSS denial – not a survey-grade or DP-grade positioning replacement. The commercial case turns on your operational profile: strong for transit through contested waters, weak as a standalone answer for DP or hydrographic work. Decide on failover budgets and spoof detection, not the rebate.
What DNK is actually offering
DNK – Den Norske Krigsforsikring for Skib, the Norwegian war-risk mutual – has opened a programme that lets members fit assured PNT (A-PNT) equipment and earn an insurance premium rebate in return. The positioning backbone is Iridium’s low-Earth-orbit satellite network. Members select their own systems from specialist technology vendors; DNK sets the incentive and recognises the resulting reduction in risk.
Two features of that framing matter before any technical discussion. First, this comes from a war-risk underwriter, not a hull-and-machinery insurer. The exposure being priced is deliberate GNSS interference – jamming and spoofing – concentrated in and around conflict zones. Second, the insurer is paying you to reduce a loss it would otherwise carry itself. That is a useful signal: the frequency and severity of GNSS denial are now large enough to move an actuarial calculation, not merely a technical talking point.
The source tells us the mechanism and the constellation. It does not tell us which vendors, what accuracy figures, or how the rebate is scaled. So the question we’d put to a survey or vessel manager is narrower and more practical: given what LEO-based PNT can and cannot do, when does taking the rebate represent genuine risk reduction, and when is it merely a box on a form?
Why GNSS denial has become an insurable risk
The threat splits cleanly into two failure modes, and they demand different defences.
Jamming denies the signal. A receiver loses lock, the position solution collapses, and – importantly – the fault is usually obvious. The bridge sees a lost fix, ECDIS flags dead reckoning, and the crew reverts to visual and radar navigation. Jamming is disruptive but generally honest about itself.
Spoofing is the harder problem. A counterfeit signal set produces a plausible, confident, and wrong position. The receiver reports a healthy fix while placing the vessel somewhere it is not, sometimes walking the reported track kilometres off truth. Everything downstream inherits the error: ECDIS, radar target correlation, AIS transmissions, and any DP position reference fed from that receiver. Spoofing defeats situational awareness precisely because it looks like normal operation.
The consequence chain runs further than most position discussions admit, because GNSS also carries time. A receiver’s 1PPS output disciplines shipboard timing used by AIS, VDR time-stamping, network synchronisation, and some communications equipment. Lose or corrupt that reference and you degrade far more than a chart position. This is why A-PNT programmes address timing as a first-class output, not an afterthought – and why Iridium’s Satellite Time and Location service is built around exactly that.
Contested waters – the eastern Mediterranean, the Black Sea approaches, the Gulf and the Strait of Hormuz, the Red Sea and Bab-el-Mandeb, and the eastern Baltic – have made these effects routine rather than exceptional. IMO addressed the operational side in MSC.1/Circ.1575, guidance on shipborne PNT data processing, and IALA has published extensively on GNSS vulnerability and resilient PNT (the R-129 material). The regulatory framework has recognised the problem for years. What DNK adds is a commercial lever.
What LEO-based PNT does, and what it does not
The engineering case for a LEO signal rests on link budget. Signals from low Earth orbit arrive far stronger at the antenna than those from GNSS satellites at roughly 20,000 km, because the range is one to two orders of magnitude shorter. A stronger received signal is materially harder to overpower with terrestrial jamming and harder to spoof convincingly, and the constellation geometry changes quickly, which complicates a deception attack. The signals are also encrypted and authenticated in the STL service, which is the property that matters against spoofing – an unauthenticated open GNSS signal offers the receiver no way to prove the transmitter is genuine.
Set against that, be clear about accuracy. LEO-based positioning of this type is navigation-grade and coarse – think tens of metres, not the metre-level of DGNSS, the decimetre of PPP, or the centimetre of RTK. Its timing output is strong; its standalone horizontal accuracy is not. So the honest description of what you are buying is threefold:
- A trustworthy timing reference that survives GNSS denial and provides holdover for time-dependent systems.
- A coarse independent position good enough for safe navigation and situational awareness when GNSS is unavailable or untrusted.
- An aiding source that bounds inertial drift. This is where the real value sits for offshore units.
That last point deserves weight. A marine inertial navigation system will coast through a GNSS outage, but it drifts, and the drift rate is set by IMU grade – a navigation-grade fibre-optic-gyro INS holds position for a useful interval, a MEMS-class unit does not. Feeding a coarse but independent LEO fix into the navigation filter arrests the unbounded growth of INS error during extended denial. In shallow water a Doppler velocity log with bottom lock does similar work. The combination – INS as the continuity engine, LEO and DVL as bounding aids – is what keeps a vessel navigating safely through hours of interference. No single box does it alone.
What LEO-based PNT does not do is replace precise positioning for production work. It will not meet IHO S-44 (Edition 6) total horizontal and vertical uncertainty limits for hydrographic survey. It will not deliver the position quality a construction or pipelay spread needs. And on its own it will not satisfy the independent position-reference requirements that IMCA guidance and DP class notation demand for close-quarters DP operations. Treat it as a resilience layer, not a survey or DP solution.
Where the decision goes wrong
1. Buying LEO PNT as a GNSS accuracy replacement
The most common misconception is that a resilient signal restores the position quality you lost. It does not. If your work requires RTK or PPP – survey, positioning of subsea structures, DP touchdown monitoring – a coarse LEO fix is a safety fallback, not a continuation of production. Scoping it as a like-for-like GNSS substitute leads to disappointment and, worse, to crews trusting a metre-critical decision to a tens-of-metres source.
2. Solving position and ignoring time
Teams fixate on the chart fix and overlook the timing cascade. If a spoof or jam corrupts the timing that disciplines AIS, VDR, and network equipment, you have a compliance and forensic problem as well as a navigation one. A programme that secures position but leaves timing exposed has closed half the gap. Specify the timing output and confirm what shipboard systems it will actually discipline.
3. Counting GNSS-based DP references as independent against a GNSS attack
This is the subtle one, and it catches good engineers. A DP2 or DP3 vessel carries multiple position reference systems for redundancy, and two of them are frequently DGNSS receivers of different make. Against a hardware fault, that is genuine diversity. Against jamming or spoofing over the operating area, it is not – both receivers share the same physical vulnerability, so the failure is common-mode. Your FMEA may show three references and still collapse to one usable input under interference. The remedy is a reference that does not depend on GNSS at all: taut wire, acoustic USBL or LBL, or relative laser/radar systems such as the fan-beam and radar-target types, backed by INS.
4. Fitting a standalone black box nobody integrates
A LEO PNT unit driving its own display in the corner of the bridge, with no path into ECDIS, the conning display, or the DP position filter, delivers little. Under stress the crew reverts to the systems they use daily. Value comes from integration – LEO and INS feeding the same navigation solution the watchkeeper already trusts, with clear indication of which source is in control.
5. Taking the rebate without defining acceptance criteria
Fitting equipment to qualify for a premium reduction, without ever testing the failover, is procurement theatre. You will not know how long the switchover takes, how far the position drifts before the backup stabilises, or whether spoof detection actually triggers, until you exercise it. The rebate rewards installation; only testing delivers the risk reduction the rebate is meant to price.
How to decide whether the rebate earns its box
The decision is driven by your operational profile against the threat geography and your accuracy requirement. Work through it in this order.
Segment the fleet by mission. For a vessel that mainly transits contested waters – a supply or standby unit, a cable ship on passage – LEO timing plus coarse position plus INS coasting is a proportionate answer, and the rebate case is strong. For a DP survey or construction unit that also needs S-44 accuracy on station, LEO is a resilience supplement layered on top of your existing precise and independent references, never a replacement for them.
Set a failover budget and test against it. Define the maximum acceptable position drift and the maximum failover latency from GNSS loss to a stable backup solution. Then run a controlled denial trial – a supervised jamming or signal-removal test, or a bench simulation with a signal generator – and confirm the numbers. Acceptance criteria first, procurement second.
Verify spoof detection, not just backup positioning. Confirm the installation cross-checks multi-constellation GNSS, applies receiver autonomous integrity monitoring, and validates against the INS and the LEO source before it trusts a fix, consistent with the intent of IMO MSC.1/Circ.1575. Detecting the deception is what prevents the confident-but-wrong fix; the backup only helps once you know GNSS is lying.
Protect DP independence explicitly. For DP2/DP3 units, treat GNSS-based references as a single common-mode input under interference in your FMEA, and ensure at least one non-GNSS position reference is available in the operating area. IMCA guidance on position reference systems is the yardstick; document how the assured PNT fit changes the failure analysis.
Integrate into the systems in use. Route the LEO/INS solution into ECDIS, the conning display, and where relevant the DP filter, with unambiguous indication of the source in control. Avoid the orphaned display.
Do the money properly. Weigh the rebate against capital cost, integration and class-approval effort, type-approval status, and lifetime maintenance. The arithmetic turns positive when a vessel spends material time in high-interference waters. It rarely does for a unit that never leaves benign areas – in which case the honest answer is that the rebate does not pay, and you should say so.
A war-risk mutual paying members to harden their PNT is a rational response to a real and rising threat. The equipment is sound and the incentive is genuine. Whether it makes commercial sense on a given hull is an engineering judgement about mission, geography, and integration – not a decision the rebate should make for you.
Based on: DNK offers program to protect ships from GNSS interference
