Russian Navy ship with GPS jammer

Better keep up the knowledge of traditional navigation methods:

Second Russian warship with ‘Pole-21’ GPS jammer fitted for naval day parade in St. Petersburg. See for first spot.
This does not appear to be a regular fit #OSINT

It can be neutralized:

Just ten years ago they still taught sextant and charts in SUNY. Hope they still do.

Got rid of paper charts a bit prematurely.

You can still manually plot on an ECDIS, as you should be doing regularly.


They are still available.

and out of radar range what are you plotting…DR?
Jaming is not the issue its sending you fake positions which in many cases you wont know.

Both jamming and spoofing are potential problems that require long-term fixes.

As far as what to do till then, I’m not sure how serious an issue it is. Ships collide and run aground fairly frequently with a good GNSS signal.

Jamming will presumably be quickly detected, as far as spoofing, as has been pointed out radar and DR is available. For spoofing to create a hazard both the source of the false signal and a navigation hazard must be nearby.

If the ship is beyond radar range there will also be fewer or no nearby navigation hazards.


If GPS is not available for whatever reason (jamming, spoofing or service interrupted at source) there are other satellite navigation systems. Many GPS receivers are able to use signals from those.
If everything else fail, break out the old sextant, nautical almanac and sight reduction tables.
That is why it is important to keep up old skills.
Keeping up the skill to keep a DR may also be important, for cloudy days.

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All the sat system frequencies are so close they will all get jammed at the same time
So yes Sextant time

At what range does the jamming device need to be?

The power requirement is very low, but given the frequency (around 1.5 GHz) it’s LoS only. There have been repeated instances of GPS jamming covering much larger areas in Northern Norway, but I have always assumed that they were from airborne devices. Norwegian sigint surely knows, but haven’t made public comments, aside from pointing at the Russians.

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Depends how you do it.
It works because the signal is very weak so all you have to do is overpower the sat signal and your in control.
Can do that locally or from above

Yes, I wrote jamming in my post but I meant spoofing. What’s the max effective range of a spoofing device?

You can actually plug your celestial fix in as a last known position and let DR mode run from there from there. During the day you’d be able to calculate set and drift off sun lines and apply that to the ECDIS’s DR too. (this does require a plotting sheet to calculate a position, or your celestial program of choice). It’d be no less accurate than running on a paper chart at this point. Running an experiment in the background of a long rhumb line leg, I found it was only a few miles off in DR mode after 12 hours, and that was only because we weren’t making as good speed as I had inputted.


Slightly less than a jamming device of equal power. A jammer just has to dirty up the signal, a spoofer has to get decent SNR at the other end. My best guess is that you could spoof a GPS signal from space, given a large phased array with enough transmitter behind it. It would be interesting if someone with actual subject matter expertise could run the numbers and say how much power you’d need.

Overpowering an omnidirectional signal with a directional one isn’t really a fair fight.

long way if a satellite is doing it

Get a hugely expensive INS like they use in subs and update by celestial when the opportunity presents itself.

I thought I saw one being developed capable of dealing with wave action in a thread around here.

Most likely, on any given ship, the low-hanging fruit as far as reducing navigation risk is going to be spending time and effort improving the use of ECDIS assuming there’s a going to be a good GNSS signal.

Putting good procedures and checklist in place to ensure that safety contours, XTE, that the safety check and so forth is being correctly used is more critical than concern about signal loss.

Then, as far as possible signal problems, make sure the GNSS signal is checked with radar overlay and in coastwise waters the watch officer regularly (once or twice a watch) plots terrestrial LOPs on the ECDIS.

Only once that’s done would I look into GNSS signal loss in open ocean scenarios. Be curious to know how accurate ECDIS is in DR mode using doppler speed thru the water (STW).


There are a few Dp vessels, when they operate in the areas where they lose gps every day, west coast Africa and parts of Brazil, that have INS.
Its accurate for about 10 minutes then drifts but if you were on a fixed course you could deal with the drift as its a known error.
INS drifts as the earth is spinning and rotating around the sun and our solar system is spiraling into the Sun.

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It would be as accurate as a DR on a paper chart assuming STW=SOG, if not more accurate because it’s real time calculations. Speed made good would be much more accurate, but the good news is this error would at least still have you on the track line, and that was a majority of the error I observed in my experiment. Sailing Pre-GPS and Loran was long before my time, but the more I look into contingencies for GPS failure, the more I realize there must have been a significant degree of winging it back in the day. I ran an exercise assuming hardware failure from say, a lightening strike, which is much more likely than a GPS being turned off all together, and with hourly fixes from an Auxiliary GPS inputted into the DR, the error was no worse than the normal allowable XTE before the next fix.

The problem being, If something were to happen I would likely go way over hours, because when I tried to explain what I was doing, everyone’s eyes just glazed over, and I’m not sure how intuitive this would be for the mariners who are, say, set in their ways. It’s a long jump from a company’s HSEQ guy who hasn’t sailed in 20 years reading this thread on how it could be done to getting useful training to a ship with a complement of officers who are "not great with computers. "

So yes, 100% more important for folks to figure out how to use the ECDIS properly before we worry about these hypotheticals. More often than not, I’d imagine that if a 3rd mate were to walk onto the ship back in the day with an equivalent paper navigation skill to today’s average senior officer’s ECDIS competency, they would be fired by the next port.