This will stir-up a hornet’s nest…

[hammdo]

https://www.airguide.info/faa-urges-pilots-to-rely-on-traditional-navigation-amid-rising-gps-spoofing-threats/
 

-Don

[DCarlton]

Imagine that.  Yes I'm in the keep your dual VOR and ILS receivers camp.  

[hammdo]

I have 1 and kept it on purpose but, no DME - that would be needed for many ‘routes’ too… I wonder how many MON VOR/ILS require DME/GPS…

-Don

[toto]

I’ve been following the e-LORAN developments with some interest. Seems like it has a future for area navigation. 

https://www.militaryaerospace.com/rf-analog/article/14181490/eloran-loran-c-gps-gnss

[hammdo]

https://hellensystems.com/

better get this going ;o)

-Don

[Marc_B]

Why does this make me think of this scene from Die Hard 2..."they've rest ground level minus 200 feet!"??? 

 

[EricJ]

A project in my pipeline is to make a lat/lon estimator using essentially the same hardware as a stratux.    The RTL-SDR tuner like what is used in a stratux will digitize enough bandwidth to receive all of the VOR channels simultaneously, so with some signal processing it can detect any VOR signals present and determine the radials of each, and estimate where the radials of multiple received VOR signals cross based on the known lat/lon of the identified VOR stations.   It won't be nearly as accurate as GPS, but will give you a good idea of where you are whenever there are at least two VORs in range.    I've done a bunch of development on the same hardware already, and also have a decent library of lat/lon computation stuff, so it's mostly just getting time to do it, and there are a few other projects in the pipeline ahead of it, unfortunately.

Somebody in the UK did something similar several years ago but it never got much attention, so it's not a unique idea.   It'd be a nice backup that you can run on a handheld device, or even on an existing stratux with an additional tuner.   I wouldn't be surprised if others aren't already working on the same and'll beat me to having something working, which is fine with me.

And, yeah, gps susceptibility to a variety of attacks is a real thing.   Everybody knows this, which is why all the global powers have their own system satellite navigation systems, to not be dependent on somebody else's.

[0TreeLemur]

1 hour ago, EricJ said:

A project in my pipeline is to make a lat/lon estimator using essentially the same hardware as a stratux.   

That's a great idea.  Knowing airspeed and heading while crossing a VOR's radials would allow you to estimate range from that VOR.  Get winds aloft from FIS-B will allow a more accurate GS estimate.  I could see a moving map display with an error ellipse around ownship.  Do it with a stratux, it'll cost less than $500.   The certified version will be $5,000 or more.  It could include DME which would be a significant improvement and more $$.

If cell phone companies would transmit time and position from each tower, that would make a fantastic constellation of surface based beacons providing essentially the capabilities as GPS.  Cell phone towers are clustered in cities and along highways so coverage wouldn't be necessarily uniform.  Less of a problem in the flight levels. 

Neat stuff.

[Pinecone]

It would just be software to do VOR/VOR position with the GTN series of navigators and some others.  You can swap back and forth with a single VOR receiver.  

Add a DME receiver (could be external) and add the ability to do VOR/DME and DME/DME position.

Heck, someone on PoA found and off the shelf solid state INS that fits in your hand for under $700.  Retail from DigiKey

When GPS is spoofed, it is normally a big difference.  So step one is to identify when you are spoofed.  Secondly, provide good enough position to get you where you are going.  But we were able to do that with VORs before GPS.

 

[hammdo]

https://www.collinsaerospace.com/what-we-do/industries/military-and-defense/navigation/airborne-products/attitude-and-heading-reference-system/micro-ins-mins

interesting…

-Don

[PeteMc]

2 hours ago, EricJ said:

Somebody in the UK did something similar several years ago but it never got much attention,

There probably wasn't any GPS Spoofing reported back when they created their device.  And very few people really think about the "what if" and have a backup plan.  Now if you did come up with a device like this, it might be of more interest.  Design in now the possibility of including an eLORAN receiver too. If they expand the system to cover the ground as well as the oceans, then it would be a simple add.  Possibly even an upgrade/retrofit to existing customers.   

And then there's always to chance you can sell your startup to Garmin to make a certified panel mount receiver that will feed your PDF. 

 

Edited February 24, 2024 by PeteMc

[EricJ]

1 hour ago, Pinecone said:

It would just be software to do VOR/VOR position with the GTN series of navigators and some others.  You can swap back and forth with a single VOR receiver.  

Add a DME receiver (could be external) and add the ability to do VOR/DME and DME/DME position.

Yeah, it's not hard to do with existing systems, but the barriers to putting something in a certified system suggest it'll be a long time and large expense.   I hope nobody is holding their breath.

1 hour ago, Pinecone said:

Heck, someone on PoA found and off the shelf solid state INS that fits in your hand for under $700.  Retail from DigiKey

The AHRS commonly used in stratux systems has mostly the same stuff for $40.   I use them just for the fan controller and get the AHRS for free.   

https://www.amazon.com/Stratux-Sensors-Controller-Raspberry-MPU9250/dp/B06ZZCHBHT

1 hour ago, Pinecone said:

When GPS is spoofed, it is normally a big difference.  So step one is to identify when you are spoofed.  Secondly, provide good enough position to get you where you are going.  But we were able to do that with VORs before GPS.

RAIM is specifically supposed to be able to detect loss or corruption of GPS.   Spoofing is supposed to be detectable as well, but who knows how sophisticated the spoofers can get.

[toto]

1 hour ago, Pinecone said:

It would just be software to do VOR/VOR position with the GTN series of navigators and some others.  You can swap back and forth with a single VOR receiver.

Doesn’t this already happen automatically? I thought I remembered that the GTN will go into a “GPS unavailable” mode and use ground-based station data to maintain navigation. 
 

ETA: Yep, here it is:

 

Not really clear whether that’s using VOR or some kind of software “best guess” about location. 

[hammdo]

My GNC 355 has that feature - no VOR so I’m guessing it takes ground speed and timing with known lat/long from the internal db and maybe wind speed/direction from the sensor into account…

-Don

[EricJ]

46 minutes ago, toto said:

Doesn’t this already happen automatically? I thought I remembered that the GTN will go into a “GPS unavailable” mode and use ground-based station data to maintain navigation. 
 

ETA: Yep, here it is:

 

Not really clear whether that’s using VOR or some kind of software “best guess” about location. 

The air data gives it airspeed and the magnetometer will give it heading, so it's probably literally dead reckoning like we used to learn for navigation, i.e., time, speed, distance, direction.   Even a good Inertial Navigation system starts accumulating drift errors as soon as it loses its reference (e.g., gps), so they're all going to provide some input, but are essentially open-loop.    I don't know of any current on-board systems that infer lat/lon/location from radio nav aids (since LORAN was turned off), which I've always thought odd since it's not that hard to do.   I suspect the absence of inexpensive AHRS/INS back in the day to fill in the gaps or maintain reliability may have kept it from being considered useful, especially once GPS became well accepted.

[toto]

28 minutes ago, EricJ said:

The air data gives it airspeed and the magnetometer will give it heading, so it's probably literally dead reckoning like we used to learn for navigation, i.e., time, speed, distance, direction.   Even a good Inertial Navigation system starts accumulating drift errors as soon as it loses its reference (e.g., gps), so they're all going to provide some input, but are essentially open-loop.    I don't know of any current on-board systems that infer lat/lon/location from radio nav aids (since LORAN was turned off), which I've always thought odd since it's not that hard to do.   I suspect the absence of inexpensive AHRS/INS back in the day to fill in the gaps or maintain reliability may have kept it from being considered useful, especially once GPS became well accepted.

Definitely. VOR-based RNAV units were reliable for enroute navigation 30 years ago, and since a modern nav unit would know where it was at the time the GNS disappeared, it could easily keep track of nearby VORs and navigate to your destination with none of the INS drift. I wonder why they don’t do this. 

[dkkim73]

3 hours ago, Pinecone said:

It would just be software to do VOR/VOR position with the GTN series of navigators and some others.  You can swap back and forth with a single VOR receiver.  

Add a DME receiver (could be external) and add the ability to do VOR/DME and DME/DME position.

As cool as the G1000 is (and I'm down on my knees thanking God for this "20 yr old technology" (which it is) since I got it) I had hoped it would also do some primitive VOR-VOR RNAV without GPS. 

I've asked a few people about adding DME and maybe ADF boxes back in... Which will integrate for basic use at least. They mostly think I'm cute for asking.

Much harder to spoof every AM station in a region than a complex GPS signal I would think (PP thoughts only, not an EWO...

Love @EricJ's SDR idea. Have read of a few cool little SDR projects recently.

D

 

[EricJ]

4 minutes ago, dkkim73 said:

Much harder to spoof every AM station in a region than a complex GPS signal I would think (PP thoughts only, not an EWO...

Love @EricJ's SDR idea. Have read of a few cool little SDR projects recently.

D

The thing I'm working on right now is for locating VHF 121.5 or 243 MHz ELTs, and could actually be used for navigating based on listening to ASOS/AWOS/ATIS AM signals.   So, in a really, really, bad pinch, as long as those don't go away there'll be a way, albeit a fairly brute-force way, to navigate with AM, even if you don't have an ADF.   

I'd been thinking about that, too, that navigating with ADF and AM broadcast stations is still a pretty reliable methodology if the "smarter" stuff started to catch colds or something, but most airplanes don't have that any more.

[Fly Boomer]

11 hours ago, hammdo said:

I have 1 and kept it on purpose but, no DME - that would be needed for many ‘routes’ too… I wonder how many MON VOR/ILS require DME/GPS…

-Don

I too plan to keep at least one copy of all my old radios (okay, not LORAN).

Searched for "how many MON VOR/ILS require DME/GPS".  First hit was this document from AOPA:

https://download.aopa.org/epilot/2012/120112VOR-MON-White-Paper.pdf

First, it says that all VORs will be retained in Alaska, the Western U.S. Mountainous Area (WUSMA), and U.S. Islands and territories. 

But outside of WUSMA, third paragraph says (in part) aircraft will be able to navigate using VOR at or above 5000 feet AGL to an airport within 100 NM and land at that airport using non-GPS-based landing aids.  Radar vectors, DME, or ADF will not be required for transit or a safe landing.  Aircraft operating in the WUSMA, Alaska, or U.S. islands or territories will have the same VOR infrastructure that is currently provided.

Document also says "primary purpose of the MON is to support safe landing of IFR aircraft during a GPS outage", so not super useful for day-to-day navigation.
 

[toto]

34 minutes ago, Fly Boomer said:

I too plan to keep at least one copy of all my old radios (okay, not LORAN).

Seriously, LORAN is looking better and better. My old GPS+LORAN combo radio isn’t going to do me much good, but I might well buy an e-LORAN receiver when that technology matures.

[Fly Boomer]

1 minute ago, toto said:

Seriously, LORAN is looking better and better. My old GPS+LORAN combo radio isn’t going to do me much good, but I might well buy an e-LORAN receiver when that technology matures.

As time goes on, LORAN is looking better and better.

[Pinecone]

8 hours ago, toto said:

Definitely. VOR-based RNAV units were reliable for enroute navigation 30 years ago, and since a modern nav unit would know where it was at the time the GNS disappeared, it could easily keep track of nearby VORs and navigate to your destination with none of the INS drift. I wonder why they don’t do this. 

Probably because no one saw a need.

There are airliners that still have DME/DME position to update the INS.

The issue has been near conflict zones and the GPS gets spoofed, and then "updates" the INS to the wrong position.  One report said the nav system showed the plane hovering (no motion) for 30 minutes.

The Garmin DR kicks in if there is no GPS signal.  With spoofing, there is a signal and the system thinks it is correct.   Since most reports show massive jumps in position and significant track changes, that the unit could be programmed to detect these and alert the pilot.

I suspect that turbine aircraft (at least larger ones) will have updates to deal with this fairly soon.

IMO, the reason that this has not been addressed was that no one saw a need.  But personally, I would have put it into the GNS series, even if just VOR/VOR back.

[dkkim73]

2 hours ago, Pinecone said:

Probably because no one saw a need.

...

The issue has been near conflict zones and the GPS gets spoofed, and then "updates" the INS to the wrong position.  

With the availability of repurpose-able technology (eg small wide bandwidth SDRs) and a certain hobbyist segment, it seems not unlikely that we might encounter some domestic use of jammers if not spoofers.  

Add a certain political vibe, eg anarchist accelerationists (like some of the odd arson of the last few years), or more familiar terrorist motivations (wait I'm sure it's all gone away) I do wonder if it's a more reasonable worry than 20 yrs ago. 

There was a presentation i read a while ago about eLORAN for tactical resiliency, very interesting. 

Disseminated poor man's RNAV like EricJ mentions would potentially have wide use. 

 

[DXB]

Interesting discussion. We clearly need eLORAN technology.  Unfortunately, a world where bad actors successfully render GPS useless will probably not be all that conducive to my continuing to fly as a fun hobby either.

[Ragsf15e]

Spoofing gps for airplanes or even jamming (which is easier) is actually pretty tough in cruise.  The jammers/spoofers are usually on the ground and need to cover a large area.  The aircraft antenna is on the top of the aircraft, providing some shielding from ground based signals.  I’d be more worried about someone tactically spoofing gps near an airport where an ac is on an approach in low weather.  In these conflict areas they are warning about, there can be many powerful jammers covering a wide area.  I think that’s unlikely outside a conflict zone.