GPS replacement

[Stevie bouy]

I’ve been thinking about how dependent we all are on GPS these days, especially offshore.


Out of interest:


• How many of you are actually concerned about GPS being unavailable or unreliable at sea?
• Does anyone here regularly use a sextant as a backup?
• For those who don’t — is that down to cost, complexity, or just not feeling the need?


Genuinely curious how people are approaching backup navigation these days.

 

[wonkywinch]

There are 4 GNSS systems, GPS is only one of them. My chart plotter can receive and decode all four (GPS, Galileo, GLONASS, and BeiDou).

 

[dunedin]

There are 4 GNSS systems, GPS is only one of them. My chart plotter can receive and decode all four (GPS, Galileo, GLONASS, and BeiDou).

But all 4 rely on very weak radio signals which are easily blocked - whether by natural phenomena or more likely human activity, accidental or malevolent. This would disable all 4 systems.
I assume the OP is reacting partly to things like the recent RIN report on GNSS blocking and spoofing.

 

[barca nova]

There is no need. Lots of satellite signals so the reliability is far greater than for a sextant which is weather dependant. But sailing round th coast, which is what most of us do, charts and a pencil / hand bearing compass etc are the back up alternative

 

[lustyd]

But all 4 rely on very weak radio signals which are easily blocked - whether by natural phenomena or more likely human activity, accidental or malevolent. This would disable all 4 systems.
I assume the OP is reacting partly to things like the recent RIN report on GNSS blocking and spoofing.

Blocking them is trivial, but requires sending a stronger signal which is even more trivial to find since it must be relatively local to the outage and direction finding kit will lead straight to the source. Bad actors, therefore, are not a problem at all outside of warzones, and most of us won't sail in warzones.
Spoofing is orders of magnitude harder to do reliable and without detection, but is already a solved problem using certificate signing of the signal. This is present on all constallations but unavailable to civilians. If spoofing became an issue, a small firmware update could enable signing and sort the issue permanently overnight. This has not happened because spoofing is simply not a real issue.

In terms of alternatives, clouds are a considerably bigger problem for sextants than spoofing or blocking are for GPS. If ever there was a need to navigate with stars, an iPhone has had all the necessary hardware for over a decade to find position accurately with stars using just the camera, realtime clock, and 9 axis accelerometer and some software. The software isn't available because....it's not an issue.

 

[Hermit]

Blocking them is trivial, but requires sending a stronger signal which is even more trivial to find since it must be relatively local to the outage and direction finding kit will lead straight to the source. Bad actors, therefore, are not a problem at all outside of warzones, and most of us won't sail in warzones.
Spoofing is orders of magnitude harder to do reliable and without detection, but is already a solved problem using certificate signing of the signal. This is present on all constallations but unavailable to civilians. If spoofing became an issue, a small firmware update could enable signing and sort the issue permanently overnight. This has not happened because spoofing is simply not a real issue.

In terms of alternatives, clouds are a considerably bigger problem for sextants than spoofing or blocking are for GPS. If ever there was a need to navigate with stars, an iPhone has had all the necessary hardware for over a decade to find position accurately with stars using just the camera, realtime clock, and 9 axis accelerometer and some software. The software isn't available because....it's not an issue.

I am not sure you can call the Baltic a war zone and, in certain areas, jamming and spoofing is prevalent. Ditto in the anchorage north of Suez (albeing close to a warzone). It is rapidly becoming a significant problem and as part of the team who developed this report (https://rin.org.uk/page/RIN_Maritime_Report) I do think back up systems are going to be of ever increasing importance.

 

[lustyd]

I am not sure you can call the Baltic a war zone

It's Russia doing the jamming and spoofing. Russia is an aggressor in a war in that area. If it were not an agressor in a war, the jamming/spoofing would have been dealt with. I won't be sailing within a few hundred miles of any of these agressive states, but you are free to do as you wish.
Commercial and military vessels might need different solutions, but they both have access to spoof-proof GNSS anyway on multiple systems so it's less of a concern for them.

 

[st599]

The NPL are reporting about how integrated GPS is in to critical UK infrastructure and how secondary sources are going to be needed very soon.

 

[requiem]

• How many of you are actually concerned about GPS being unavailable or unreliable at sea?

Not really concerned; I'm not sailing in areas where jamming is frequent, so the closest it gets is the occasional Notice to Mariners about "GPS might not be working within X miles of {location} due to testing during {time range}".

If it does happen; there isn't really an issue; I can just as easily plot a traditional or radar fix on my devices. I keep a sextant around mainly for practice as I'm rarely so far offshore that it would make a meaningful difference.

 

[st599]

Not really concerned; I'm not sailing in areas where jamming is frequent, so the closest it gets is the occasional Notice to Mariners about "GPS might not be working within X miles of {location} due to testing during {time range}".

If it does happen; there isn't really an issue; I can just as easily plot a traditional or radar fix on my devices. I keep a sextant around mainly for practice as I'm rarely so far offshore that it would make a meaningful difference.

The bigger issue is that financial transactions, water provision and food transport logistics would also grind to a halt as they're reliant on GNSS. But you may not know as most communication networks are too.

 

[requiem]

The bigger issue is that financial transactions, water provision and food transport logistics would also grind to a halt as they're reliant on GNSS. But you may not know as most communication networks are too.

Oh, I suspect if that day ever comes the extra sunrises will provide a clue.

 

[Hermit]

I think that GNSS disruption is going to become more widespread and potentially mobile on hostile state vessels. I hope no one is planning a charter from Antalya. GPSJAM GPS/GNSS Interference Map

 

[st599]

Oh, I suspect if that day ever comes the extra sunrises will provide a clue.

Not according to the UK government. Landmark government investment to safeguard the essential signals we all rely on

 

[Roberto]

I would immediately tie three Ariadne's strings to wife and daughters to avoid having to travel to Congo or Oklahoma to find them back.

 

[dunedin]

The bigger issue is that financial transactions, water provision and food transport logistics would also grind to a halt as they're reliant on GNSS. But you may not know as most communication networks are too.

The RIN report made this point on a smaller scale. Lots of systems on ships are needlessly integrated to GNSS, often for time etc, which means a GNSS outage can have many unexpected knock on failures.
Better design would reduce our impact from GNSS unavailability.

 

[st599]

The RIN report made this point on a smaller scale. Lots of systems on ships are needlessly integrated to GNSS, often for time etc, which means a GNSS outage can have many unexpected knock on failures.
Better design would reduce our impact from GNSS unavailability.

NPL are starting to offer terrestrial time broadcasts and more accurate timing over IP connections.