Alternatives to GPS

[Forest Green]

DIU to fund ‘unjammable’ magnetic navigation tech​

DIU expects to fund prototypes of multiple airborne platforms for magnetic navigation, including one that scans the ocean surface at 2,000 ft.

DIU to fund 'unjammable' magnetic navigation tech - Breaking Defense

DIU expects to fund prototypes of multiple airborne platforms for magnetic navigation, including one that scans the ocean surface at 2,000 ft.

breakingdefense.com

 

[zjz]

Similar article from Aviation Week, although I have no paid subscription so I do not have the full article ....

Quantum Sensors Boost Magnetic Navigation As An Alternative To GPS | Aviation Week Network

Quantum sensing is ready to transition from the laboratory to operations, led by ultrasensitive magnetometers for magnetic navigation.

aviationweek.com

 

[zjz]

Can quantum sensing improve magnetic navigation? Pentagon thinks one company is on the right track​

Can quantum sensing improve magnetic navigation? Pentagon thinks one company is on the right track

The Defense Department is looking to speed up deployment of new GPS alternatives.

www.defenseone.com

 

[Forest Green]

https://twitter.com/x/status/2036458083480723800

View: https://x.com/DARPA/status/2036458083480723800?s=20

ROCkN: Robust Optical Clock Network​

ROCkN: Robust Optical Clock Network | DARPA

This program seeks to develop optical precision timing technologies to significantly increase the precision and holdover of DoW timing capability in low-size, weight, and power (SWaP) devices that can operate outside the lab.

www.darpa.mil

Over the past two decades, precision timing in the optical domain has advanced rapidly in the laboratory and has recently surpassed – in stability and precision – the ubiquitous microwave timing techniques that make up the foundations of global precision timing in commercial and Department of War (DoW) domains.

Optical precision timing techniques provide a means for orders of magnitude higher precision and accuracy, but, just as importantly, they enable more resilient timing capabilities with less reliance on GPS by virtue of longer holdover times and usage of optical signals that are more difficult to jam or spoof.

The “Robust Optical Clock Network” (ROCkN) program seeks to develop optical precision timing technologies to significantly increase the precision and holdover of DoW timing capability in low-size, weight, and power (SWaP) devices that can operate outside the lab.

ROCkN has two Technical Areas (TA) based on different application domains:

• TA1 aims to develop small portable clocks that provide the time precision necessary for distributed coherent sensing and other applications in a robust package suitable for airborne or spaceborne platforms
• TA2 aims to develop transportable clocks with month-long holdover of GPS-quality precise time and autonomous operation, with a view toward providing a local regional time scale on land or seaborne platforms

ROCkN enables GPS-free operations​

ROCkN enables GPS-free operations | DARPA

The Robust Optical Clock Network (ROCkN) program enables precision timekeeping, even in contested and/or GPS-denied environments.

www.darpa.mil

 

[ew33]

DIU to fund ‘unjammable’ magnetic navigation tech​

DIU expects to fund prototypes of multiple airborne platforms for magnetic navigation, including one that scans the ocean surface at 2,000 ft.

DIU to fund 'unjammable' magnetic navigation tech - Breaking Defense

DIU expects to fund prototypes of multiple airborne platforms for magnetic navigation, including one that scans the ocean surface at 2,000 ft.

breakingdefense.com

Yup essentially TERCOM but earth's EMI instead of SAR imagery

 

[Owens Z]

DIU expects to fund prototypes of multiple airborne platforms for magnetic navigation, including one that scans the ocean surface at 2,000 ft.

Similar article from Aviation Week, although I have no paid subscription so I do not have the full article

Yup essentially TERCOM but earth's EMI instead of SAR imagery

Thanks zjz. I read that same recent article (Aviation Week & Space Technology, 12 Jan 2026 pp29-30) about the prospects for magnetic navigation and found it very interesting. I had heard that the in-development quantum nitrogen-vacancy diamond magnetometers described in the article will (unlike signals from navigation satellites) work in caverns, or underwater, and be unaffected by today's electronic warfare jamming and spoofing. The article mentions future trials of magnav in airplanes at 30,000 feet, so that distance from Earth's surface is not prohibitive. Therefore I wonder whether magnav in low Earth orbit could in principle be workable. If yes, then publicly available magnetic field maps of all Earth in much greater detail (which the AWST article admits are needed before magnav can become practical) might be charted from space, sidestepping possible objections by some countries to ground or aerial geophysical surveys inside their borders. And perhaps magnav, given appropriate maps, could find use on the Moon and Mars someday.

The AWST article includes the intriguing sentence "Quantum gravimeters measure small variations in local acceleration due to gravity, which can be similarly matched to gravitational maps", but doesn't follow up. Gravitational field navigation, if ever practical, would be yet another alternative method of navigation, likewise unjammable. The mascons very noticeable from lunar orbit (as discovered in the 1960s) might make such a method especially suitable on the Moon.

 

[Owens Z]

With the jamming (no usable signal) and spoofing (misleading signal) that have increasingly become a concern for GPS and other satellite navigation systems in this 21st century, I have seen some rueful comments that it might have been shortsighted to discontinue in 1997 the US Coast Guard's successful 'Omega' very-low-frequency navigation system. Several lofty antenna towers around the globe provided continuous worldwide coverage, transmitting powerfully at frequencies around 10-14 kHz, which made Omega resistant to any practical jamming (although just prior to an all-out war, one or more of the remote towers might have been vulnerable to commando teams packing dynamite). Unlike GPS, Omega was usable by submerged submarines if not too deep. Omega's positional accuracy wasn't comparable to GPS, or even to a sextant with chronometer, but its fixes were found to be close enough for general military and civilian use. After the towers were built Omega was a relative pittance to operate (far less per year than the cost of one satellite launch). If allowed to continue, Omega would remain a robust and cheap alternative to satnav when and where needed. Too late now to reconsider—most of the towers were dismantled.

I know the similar Soviet РСДН-20 or 'Alpha' VLF navigation system continued in service after 1997, but I don't know whether or not Alpha still transmits. Anybody here have info?

 

[Owens Z]

The few hundred pulsars that have been charted so far by x-ray astronomy, each with its exact position and unique pulse fingerprint recorded, could in principle be plotted by an x-ray-detecting device aboard a spacecraft that continuously determines attitude and position anywhere in our solar system, for the spacecraft's autonomous piloting, as a complement or alternative to existing optical star trackers/stellar compasses with their catalog of bright stars. If I'm understanding correctly, preliminary experiments in x-ray pulsar navigation (XNAV) like NICER/SEXTANT, launched to the International Space Station in 2017, have been promising.

For an alternative to GPS here on Earth, while x-rays don't penetrate our atmosphere the several thousand pulsars that radio astronomers have charted so far might be plotted by a similar device on an airplane, ship, or ground vehicle that receives microwaves. Some teams have been working on this concept, it's been reported. Each pulsar is faint, but unlike a navigation satellite's signal its distinctive emission is smeared over a broad spectrum of radio frequencies, so that current electronic warfare jamming or spoofing wouldn't be effective. And pulsars cannot be shot down.

 

[ew33]

There is also this research paper talking about it

Quantum-assured magnetic navigation achieves positioning accuracy better than a strategic-grade INS in airborne and ground-based field trials

Modern navigation systems rely critically on GNSS, which in many cases is unavailable or unreliable (e.g. due to jamming or spoofing). For this reason there is great interest in augmenting backup navigation systems such as inertial navigation systems (INS) with additional modalities that reduce...

arxiv.org

 

[Byeman]

With the jamming (no usable signal) and spoofing (misleading signal) that have increasingly become a concern for GPS and other satellite navigation systems in this 21st century, I have seen some rueful comments that it might have been shortsighted to discontinue in 1997 the US Coast Guard's successful 'Omega' very-low-frequency navigation system.

It wasn't accurate enough

 

[Owens Z]

[Omega] wasn't accurate enough

If the choice ever comes down to be between something and nothing, Byeman, that's not a difficult decision. Satellites are susceptible, hence the modern search for practical alternate means of position fixing (complementing dead reckoning), just in case. That such alternate means might be less accurate, even much less accurate, than present satellite navigation at unjammed peak efficiency is regrettable, but not prohibitive.

For two decades, the US Naval Academy in Annapolis gave up teaching traditional celestial navigation, because the more accurate GPS "will always be available". Then ten years ago, with the vulnerability of satellites and satellite signals increasingly obvious, a prudent decision was made to reintroduce training with sextant, non-GPS chronometer, and hard-copy charts. I believe the US Coast Guard wisely made the same reversion. Sextants are not hackable, though unlike the Omega and Alpha VLF navigation systems, they are unusable while the Sun or stars can't be sighted from deck, e.g. when overcast, or submerged.

 

[Byeman]

There still is IRS.

 

[Kat Tsun]

Daylight celestial navigation is probably the winner in GPS denied environments.

 

[Josh_TN]

A much simpler technology might be simply exploiting the Starlink constellation, which is extremely hard to jam or destroy:

https://people.engineering.osu.edu/media/document/2025-10-31/barrett_high_altitude_and_high_latitude_exploiting_starlink_and_oneweb_leo_satellite_signals_for_opportunistic_navigation_in_extreme_environments.pdf

In the future other LEO constellations will provide such services as well. I believe Starlink is now providing an actual service for this now rather than just being an emitter of opportunity, and the Iridium constellation provides location information on its old pager service carrier wave. The new SDA satellites with link 16 are going to provide a secondary navigation service. I think a new start up intends to build a dedicated commercial LEO nav system as well.

 

[Owens Z]

There still is IRS.

You might have Internal Revenue Service on your brain with the tax deadline coming up, Byeman, but I believe you meant INS or inertial navigation system, a machine for automated dead reckoning. INS has come a long way since the 1950s units for ballistic missiles and submerged nuclear submarines, and I've seen news reports that quantum this-and-that will result in even more exacting precision in the future. But a fundamental weakness of dead reckoning is that the process must begin from a known, charted waypoint. If the process begins instead from a satnav fix that an enemy has spoofed to be mistaken, which has happened, then everything after that is tainted, on the principle 'garbage in, garbage out'.

At the very least, a reasonably alert man familiar with traditional navigation constrains a spoofer to keep his lies plausibly close to the truth, rather than give the worthless nonsense he would prefer ("No, you're not in the Barents Sea—you are just east of Tahiti"). So I applaud continued training in traditional navigation.

 

[Byeman]

You might have Internal Revenue Service on your brain with the tax deadline coming up, Byeman, but I believe you meant INS or inertial navigation system, a machine for automated dead reckoning. INS has come a long way since the 1950s units for ballistic missiles and submerged nuclear submarines, and I've seen news reports that quantum this-and-that will result in even more exacting precision in the future. But a fundamental weakness of dead reckoning is that the process must begin from a known, charted waypoint. If the process begins instead from a satnav fix that an enemy has spoofed to be mistaken, which has happened, then everything after that is tainted, on the principle 'garbage in, garbage out'.

At the very least, a reasonably alert man familiar with traditional navigation constrains a spoofer to keep his lies plausibly close to the truth, rather than give the worthless nonsense he would prefer ("No, you're not in the Barents Sea—you are just east of Tahiti"). So I applaud continued training in traditional navigation.

IRS - inertial reference system.
Back in the day, every hangar had its location stenciled on the wall.

 

[Owens Z]

A much simpler technology might be simply exploiting the Starlink constellation, which is extremely hard to jam or destroy:
In the future other LEO constellations will provide such services as well. I believe Starlink is now providing an actual service for this now rather than just being an emitter of opportunity, and the Iridium constellation provides location information on its old pager service carrier wave. The new SDA satellites with link 16 are going to provide a secondary navigation service. I think a new start up intends to build a dedicated commercial LEO nav system as well.

An interesting paper; thanks Josh_TN. Starlink's thousands of satellites in low Earth orbit are closer to users than the few dozen dedicated navigation satellites in higher orbits, so numbers and the inverse-square law mean more powerful signals on the ground. I know nothing about details, but I've heard thirdhand that Starlink's successful robustness is also due to behind-the-scenes efforts from highly motivated American, Ukrainian, and Israeli experts over the past six years to overcome persistent, nastily intensive electronic warfare and cyberattack against Starlink from Russia and Communist China, as well as a few less accomplished countries.

Of course, highly motivated can go both ways. A determined enemy may decide, rather than deal with a swarm of existing satellites, to send commando teams with dynamite to the vulnerable two or three places on Earth where such satellites can be launched to space.

 

[Owens Z]

IRS - inertial reference system. Back in the day, every hangar had its location stenciled on the wall.

Ahhh, I see—a synonym.

 

[Void]

If the choice ever comes down to be between something and nothing, Byeman, that's not a difficult decision. Satellites are susceptible, hence the modern search for practical alternate means of position fixing (complementing dead reckoning), just in case. That such alternate means might be less accurate, even much less accurate, than present satellite navigation at unjammed peak efficiency is regrettable, but not prohibitive.

For two decades, the US Naval Academy in Annapolis gave up teaching traditional celestial navigation, because the more accurate GPS "will always be available". Then ten years ago, with the vulnerability of satellites and satellite signals increasingly obvious, a prudent decision was made to reintroduce training with sextant, non-GPS chronometer, and hard-copy charts. I believe the US Coast Guard wisely made the same reversion. Sextants are not hackable, though unlike the Omega and Alpha VLF navigation systems, they are unusable while the Sun or stars can't be sighted from deck, e.g. when overcast, or submerged.

Hopefully they will eventually figure out you can use a phone app for celestial navigation.

 

[DWG]

Hopefully they will eventually figure out you can use a phone app for celestial navigation.

Not if someone takes out your phone with a zero day exploit. Difficult to hack a pen and paper.

 

[Kat Tsun]

Not if someone takes out your phone with a zero day exploit. Difficult to hack a pen and paper.

It's also infinitely easier to go off course due to bad calculations and requires semi-constant training and use outside of the Academy.

The real limit in modern combat is that you need skills that don't atrophy over time after all, because Sailors rarely have time to practice things outside of their job duties, and that apparently includes basic navigation. USN warships have much more common and serious issues, like their helm control touchscreens going out or their watchstanders missing the cargo ship 500 meters off the starboard bridge wing, than any possible cellphone hack.

ATAK uses a DOD proprietary fork of Android and you wouldn't need to have a phone with networking to use it as a sextant. You can download a celestial map and run the phone offline.

Even then, Ukrainian artillerists have no trouble using Discord and Signal on their phones and laptops for fire missions and vice versa the Russians. Sometimes they get into each other's voice calls and give bad info but it hasn't even shifted the frontline. The idea that cellphones are vulnerable to REC is a bit silly given the two largest combat users of cellphones since 2014 have found them indispensable once their LIC turned into an "LSCO"/HIC back in 2022. If they were truly vulnerable, that would be the first thing to go, and neither Russian nor Ukrainian gunners seem bothered to use their phones nor have there been any groundbreaking REC victories.

Elon turning off Russia's jailbroken Starlinks did more damage than any cellphone REC efforts done by CIA or HUR. Or for that matter, SVR and GRU. If the phones were a problem it would have been apparent over the past four years of high intensity combat in Europe. They only seem to be dangerous in low intensity anti-terrorist actions. They get lost in the electronic smoke of modern battle in a HIC.

Besides that, it would be trivial to give the warship itself the necessary cameras and have them use it for celestial navigation automatically.