When GPS Lies: The Navigation Failure More Dangerous Than Losing the Signal
There is a particular kind of failure every navigator understands.
A screen goes blank. A receiver loses its fix. An alarm appears. Whatever caused it, you know immediately that one of your navigation sources is gone.
That can be serious, but at least the failure has announced itself.
A different problem begins when the equipment continues working.
The boat symbol still moves across the electronic chart. Latitude and longitude continue updating. Course and speed look reasonable. Nothing appears broken.
Except the position is wrong.
That is the problem behind GPS spoofing, and it is becoming increasingly relevant to shipping, aviation and critical infrastructure.
I have spent much of my working life navigating, both at sea and in the air. Losing a navigation source is inconvenient and, depending on circumstances, potentially dangerous. But a believable false position creates a different problem.
Before you can deal with the failure, you first have to recognize that there is one.
Jamming and spoofing are not the same thing
Most of us use the word GPS for satellite navigation generally. More accurately, GPS is one part of GNSS, the Global Navigation Satellite Systems that also include Europe's Galileo, Russia's GLONASS and China's BeiDou.
Two kinds of interference are particularly important.
Jamming overwhelms or interferes with the satellite signals so that the receiver can no longer use them properly.
Spoofing attempts to deceive the receiver by introducing false information.
From the navigator's point of view, the distinction matters.
If the receiver loses its position completely, I know I need another way of establishing where I am.
If the receiver continues showing a plausible position that is wrong, I may initially have no reason to distrust it.
That is a much more interesting problem.
Norway has been testing exactly this
In September 2026, hundreds of specialists from more than twenty countries gathered at Andøya in northern Norway for Jammertest 2026.
Under controlled conditions, navigation equipment was deliberately exposed to GNSS jamming, spoofing and other forms of interference.
The intention was not theoretical research alone. Aircraft, vehicles, receivers and other systems could be tested under conditions that are difficult to reproduce safely anywhere else.
The warnings issued for the exercise included the possibility of lost GPS reception, unstable positioning and incorrect position or time information.
That last point matters.
Satellite navigation is not only about position.
It is also about time.
The hidden part of GPS
Most people encounter GPS through something visible.
A car shows where to turn.
A phone shows a blue dot on a map.
A ship moves across an electronic chart.
An aircraft navigation system calculates its route.
But GNSS also provides extremely precise timing.
Telecommunications networks, surveying, mapping and parts of modern digital infrastructure rely on accurate time synchronization derived from satellite systems.
Norway is already working on ways of distributing precise national time independently of GNSS because of the vulnerability created when too many systems rely on the same external source.
This is one of the more interesting things about technological dependence.
The systems that matter most are often the ones ordinary users barely notice.
So what does a false GPS position actually look like?
Sometimes the answer is obvious.
A vessel suddenly appears on land.
The position jumps several kilometres.
The calculated speed becomes impossible.
The electronic chart bears no resemblance to what can plainly be seen outside.
Those failures should be noticed quickly.
The harder case is when the error remains believable.
Imagine running along a coastline.
According to the chartplotter, everything looks normal.
Then the lighthouse bears slightly farther to port than it should.
Radar places the headland somewhere different from the GPS position.
The depth sounder shows twenty metres beneath the keel when the electronic chart at the displayed position suggests considerably deeper water.
One disagreement might have an innocent explanation.
The lighthouse bearing may be poorly taken. The radar picture may be cluttered. The charted depth may not exactly match the bottom.
But when several independent sources begin disagreeing with the GPS position, the problem changes.
Now the navigator has to decide which information deserves confidence.
That is a very different task from following the little boat symbol across the screen.
The instruments have to agree with the world outside
Good navigation has never meant accepting one instrument without question.
At sea, there are many ways to challenge a position.
Radar ranges can establish distance from a known object.
Radar bearings can help locate a vessel relative to land.
Visual bearings can be taken from lighthouses, headlands and other charted features.
The echo sounder tells you what is actually beneath the hull.
The magnetic compass gives information independent of satellite navigation.
Speed, elapsed time, wind, current and tide tell you roughly where the vessel should have travelled.
Dead reckoning provides another estimate.
When circumstances allow it, celestial navigation provides yet another independent source.
None of these is infallible.
That is not a weakness. It is one reason several of them are useful together.
If the GPS position says I should have forty metres beneath the keel but the sounder says twelve and falling, I am interested in the sounder.
If radar puts a headland somewhere the chartplotter says it should not be, I want to know why.
If the lighthouse is appearing on the wrong bearing, I check it again.
The navigator is not there merely to read coordinates. The job is to compare information and notice when the pieces stop fitting together.
The little blue dot changed navigation
Before satellite navigation, uncertainty was something navigators lived with openly.
A dead-reckoning position was never an exact point in the modern sense.
You knew your last reliable fix. You knew your heading, estimated speed and elapsed time. Then wind, current, steering error and imperfect information slowly widened the possible difference between where you calculated yourself to be and where you actually were.
A celestial fix had limitations.
Visual bearings had limitations.
Charts had limitations.
The navigator knew that.
Modern satellite navigation changed the experience.
The position displayed by a good GNSS receiver is usually extraordinarily accurate. The electronic chart places the vessel neatly over its calculated coordinates. The numbers update continuously. The presentation is clean and precise.
Most of the time, trusting it is entirely reasonable.
That reliability is exactly what makes spoofing troublesome.
People become accustomed to the instrument being right.
And once an instrument has been right ten thousand times, questioning it on the ten-thousand-and-first occasion does not come naturally.
Aviation faces the same problem
This is not only a maritime issue.
GNSS interference has become an increasing concern in aviation, particularly in regions where jamming and spoofing occur regularly.
A modern aircraft has far more information available than a single GPS receiver, but the underlying problem remains familiar to any navigator.
Does the position indicated by one system agree with the other information available?
Does the aircraft appear to be where its instruments say it is?
Do independent navigation sources agree?
Are heading, position, timing and the expected route still making sense together?
A professional crew does not need to distrust every instrument in front of them.
They need to recognize when something no longer fits.
That distinction matters.
Northern Norway is already seeing consequences
The issue is not confined to exercises at Andøya.
Kartverket, the Norwegian Mapping Authority, has reported increasing problems with satellite interference during aerial mapping in northern Norway.
Accurate aerial photography and mapping depend heavily on knowing exactly where the aircraft and its sensors are when data is collected.
When GNSS becomes unreliable, the effect reaches beyond the cockpit.
The mapping data itself can be affected.
That is a useful example of how deeply satellite positioning has become embedded in modern systems.
A navigational problem in an aircraft can become a surveying problem.
A surveying problem can become a mapping problem.
The dependency extends outward.
Do we need to bring back the sextant?
Not in the way that question is sometimes presented.
I would choose functioning modern satellite navigation over a sextant and astronomical tables almost every time.
Modern GPS and Galileo receivers are remarkable.
Electronic charts are remarkable.
Radar is remarkable.
Modern aircraft navigation systems would have seemed almost impossible to navigators only a few generations ago.
The answer to GNSS vulnerability is not to abandon those systems.
It is to understand what happens when they are unavailable or wrong.
That is where older and independent methods remain valuable.
A magnetic compass does not depend on the GPS constellation.
Radar can show where the coastline physically is regardless of where the satellite receiver believes the vessel is.
An echo sounder reports the water beneath the keel.
Dead reckoning tells you approximately where you should be based on where you started and how you have travelled.
A sextant allows a navigator to obtain information from celestial bodies without receiving anything from a satellite network.
None replaces everything else.
They simply fail in different ways.
Two screens do not necessarily mean two independent systems
This is something easily overlooked in modern equipment.
A vessel may have several displays showing position.
A phone has GPS.
A tablet has GPS.
The chartplotter has GPS.
Another receiver may have GPS.
It looks like redundancy.
But if every device depends on the same satellite signals, they may all be vulnerable to the same problem.
Independent navigation is more useful when the sources themselves are genuinely different.
Satellite navigation provides one answer.
Radar provides another.
The compass provides another piece of information.
The echo sounder provides another.
Visual observations provide another.
Dead reckoning provides another.
The navigator compares them.
Most of the time they agree closely enough that nothing interesting happens.
The interesting moment comes when they do not.
This is close to the opening of SOLSTORM
The question sits quietly behind the opening of SOLSTORM: The Sky Went Wrong.
Erika is alone aboard a small sailboat south of Iceland when the modern navigational systems around her begin failing.
Her GPS dies.
The radio gives her nothing useful.
The compass becomes unreliable.
What she has left are paper charts, a sextant, a chronometer, dead reckoning, the sky, the sea and the things an older sailor taught her before she ever expected to need them.
I did not write that scene because I believe old technology is better than new technology.
It isn't.
I wrote it because I find dependence more interesting than technology itself.
What do we still know how to do when the system we normally use stops answering?
GPS spoofing creates a harder version of the same question.
What happens when the system still gives us an answer, and we have to recognize that the answer no longer fits what is actually around us?
For a navigator, that is where the work begins.
Modern navigation systems have made travelling by sea and air vastly safer and more precise than it once was. We should use them.
But every so often it is worth looking away from the screen.
Check the radar.
Check the depth.
Check the compass.
Look at the headland.
Look at the lighthouse.
And make sure the world outside still agrees with the position inside the machine.
SOLSTORM: The Sky Went Wrong begins in the North Atlantic when modern systems fail and the knowledge people assumed they no longer needed suddenly matters again.
