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Decoding DME aircraft radio navigation system with the LimeSDR

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Re: Decoding DME aircraft radio navigation system with the LimeSDR

#11

Post by ammar2 »

ryandrake wrote: post #10
aftbit wrote: post #9

Earlier quoted context omitted.

There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. For example, combat zones often employ GPS spoofing and jamming, and because radio waves don't exactly respect borders, this can sometimes affect civilian equipment outside of the combat zone. This has happened at least near Israel, Iraq, and Ukraine in the last few years. In…

> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.

The VOR Minimum Operation Network[1] in the US is basically supposed to be that. They're decommissioning a lot of the VORs but at least guaranteeing that you'll be 100NM away from a working VOR and an airport with an approach that can be accomplished with VORs for the initial fixes.

Still definitely feels like putting a lot of reliance on GPS but at least there's a backup for the worst case.

[1] https://www.faa.gov/about/office_org/headquarters_offices/at...

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#12

Post by _djo_ »

aftbit wrote: post #9
VBprogrammer wrote: post #3

Earlier quoted context omitted.

ADF uses radio direction finding techniques. It's not very accurate and is all but deprecated except for some corner cases where the legislation hasn't yet allowed for overlay approaches (replacing a real radio beacon with its true position via GPS / IRS). There are some convincing reasons for being cautious on general on that front. Accidents have happened because some beacons have been substituted for the wrong loc…

There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. For example, combat zones often employ GPS spoofing and jamming, and because radio waves don't exactly respect borders, this can sometimes affect civilian equipment outside of the combat zone. This has happened at least near Israel, Iraq, and Ukraine in the last few years. In…

It's currently happening in the Eastern DRC too, affecting not only scheduled commercial traffic but humanitarian flights as well.

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#13

Post by tjohns »

VBprogrammer wrote: post #3
deutschepost wrote: post #2

VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR. But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.

ADF uses radio direction finding techniques. It's not very accurate and is all but deprecated except for some corner cases where the legislation hasn't yet allowed for overlay approaches (replacing a real radio beacon with its true position via GPS / IRS). There are some convincing reasons for being cautious on general on that front. Accidents have happened because some beacons have been substituted for the wrong loc…

NDBs/ADF are much more common outside the US, where there isn't a huge installed VOR network or where there is a need for long-range airways over remote terrain. (Canada, I'm looking at you.)

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#14

Post by tjohns »

ammar2 wrote: post #11
ryandrake wrote: post #10

Earlier quoted context omitted.

> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.

The VOR Minimum Operation Network[1] in the US is basically supposed to be that. They're decommissioning a lot of the VORs but at least guaranteeing that you'll be 100NM away from a working VOR and an airport with an approach that can be accomplished with VORs for the initial fixes. Still definitely feels like putting a lot of reliance on GPS but at least there's a backup for the worst case. [1] https://www.faa.gov/a…

There's also a DME Minimum Operational Network, for airliners that can use DME-DME RNAV. (That's too expensive for smaller aircraft to install, though.)

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#15

Post by toomuchtodo »

ryandrake wrote: post #10
aftbit wrote: post #9

Earlier quoted context omitted.

There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. For example, combat zones often employ GPS spoofing and jamming, and because radio waves don't exactly respect borders, this can sometimes affect civilian equipment outside of the combat zone. This has happened at least near Israel, Iraq, and Ukraine in the last few years. In…

> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.

> you need a redundant backup navigation system that is robustly deployed and reliably works.

Could existing cellular network base stations be this ground based backup navigation system?

https://people.engineering.osu.edu/sites/default/files/2022-...

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#16

Post by nradov »

ryandrake wrote: post #10
aftbit wrote: post #9

Earlier quoted context omitted.

There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. For example, combat zones often employ GPS spoofing and jamming, and because radio waves don't exactly respect borders, this can sometimes affect civilian equipment outside of the combat zone. This has happened at least near Israel, Iraq, and Ukraine in the last few years. In…

> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.

I agree. Starlink could potentially be used as an alternative to GPS (and other similar constellations). But it will probably be a long time, if ever, before it's certified for civil aviation navigation. And it's also vulnerable to jamming.

https://www.technologyreview.com/2022/10/21/1062001/spacex-s...

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#17

Post by cameldrv »

tjohns wrote: post #14
ammar2 wrote: post #11

Earlier quoted context omitted.

The VOR Minimum Operation Network[1] in the US is basically supposed to be that. They're decommissioning a lot of the VORs but at least guaranteeing that you'll be 100NM away from a working VOR and an airport with an approach that can be accomplished with VORs for the initial fixes. Still definitely feels like putting a lot of reliance on GPS but at least there's a backup for the worst case. [1] https://www.faa.gov/a…

There's also a DME Minimum Operational Network, for airliners that can use DME-DME RNAV. (That's too expensive for smaller aircraft to install, though.)

It's too bad that DME/DME RNAV isn't more widely available. The only real reason it's so expensive is that there isn't much demand for it since GPS (usually) works fine. Electronics-wise, it's not much more complicated than a transponder. Unlike a GPS, it does have to transmit, so it will always be somewhat more expensive than GPS.

The other problem is that there's a limit to how many aircraft a DME station can serve at a time (about 100), but I believe that could be greatly expanded if aircraft weren't pinging the DME so often. A position fix every second is generally fine, and it could be even more infrequent if you have a cheap inertial system to fuse with it that can fill in the track for a few seconds between pings.

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#18

Post by mikewarot »

nradov wrote: post #16
ryandrake wrote: post #10

Earlier quoted context omitted.

> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.

I agree. Starlink could potentially be used as an alternative to GPS (and other similar constellations). But it will probably be a long time, if ever, before it's certified for civil aviation navigation. And it's also vulnerable to jamming. https://www.technologyreview.com/2022/10/21/1062001/spacex-s...

Starlink and GPS always face denial of service from exterior forces, or simply not being able to launch replacements up into orbit in a timely manner.

We should ALWAYS have full coverage from ground based navigation systems, and the pilots should be required to use them on a regular basis.

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#19

Post by someguydave »

toomuchtodo wrote: post #15
ryandrake wrote: post #10

Earlier quoted context omitted.

> There's also a very real chance that commercial aviation may find itself operating in a GPS-denied environment, at least in various edge cases. Yea, it's kind of terrifying that we are slowly putting all of our eggs in the GPS basket. I love GPS but when lives are at stake, you need a redundant backup navigation system that is robustly deployed and reliably works.

> you need a redundant backup navigation system that is robustly deployed and reliably works. Could existing cellular network base stations be this ground based backup navigation system? https://people.engineering.osu.edu/sites/default/files/2022-...

Sure it could be done but good luck convincing cell phone vendors to adopt liability for aircraft safety

Re: Decoding DME aircraft radio navigation system with the LimeSDR

#20

Post by 0xfaded »

deutschepost wrote: post #2

VORs are pretty interesting. At first i thought every plane had a small antenna array on board to check the direction to the VOR. But the direction is just calculated by the phase shift between an omnidirectional and a directional signal. So it can be implemented very cheaply on every plane.

Here is the authoritative video of an English radio engineer explaining how VOR works.

It truly is 60s level wizardry.

https://youtu.be/tZ2gG1v9Xg8

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