Are the days of satellite GPS navigation numbered??

[K_V_B]

Originally Posted by Johan Leopard51

GPS is at times deliberately offset.

Besides time on boats we also spend time overlanding / Safari in Africa. More than once I have had our Land Cruiser physically in a town at known landmark like police station but Garmin say I’m 15 miles away.

I doubt that this is your GPS being inaccurate. The maps are probably off. A lot of errors in maps are being discovered thanks to GPS. And you may have the wrong datum set etc...

[IanTrail]

We use GPS all the time; it would be silly and irresponsible not to. But we did learn how to use a sextant for our first ocean crossing, and we used it every day, mostly for fun, partly get get proficient at it but mainly because a 17 day ocean passage can get very boring!

Our main concern was not the GPS system being unavailable but us being unable to receive it. An electrical failure or an equipment failure due to a fault, flooding or lightning strike. The one we got was a lightning strike. We have an encapsulated keel so it's difficult to fit a permanent lightning ground so we have one which we throw over the side and connect it to the base of the mast with a big fat cable. The lightning ground took most of the strike but where the cable went across the deck then over the side we got some side flashes onto internal wiring. (Lightning strikes don't like making sharp bends). So we lost some electronics; not the GPS as it happened but it could easily have been.

So a sextant is part of our essential equipment, like the eye patch and the parrot.

[Statistical]

Originally Posted by IanTrail

We use GPS all the time; it would be silly and irresponsible not to. But we did learn how to use a sextant for our first ocean crossing, and we used it every day, mostly for fun, partly get get proficient at it but mainly because a 17 day ocean passage can get very boring!

Our main concern was not the GPS system being unavailable but us being unable to receive it. An electrical failure or an equipment failure due to a fault, flooding or lightning strike. The one we got was a lightning strike. We have an encapsulated keel so it's difficult to fit a permanent lightning ground so we have one which we throw over the side and connect it to the base of the mast with a big fat cable. The lightning ground took most of the strike but where the cable went across the deck then over the side we got some side flashes onto internal wiring. (Lightning strikes don't like making sharp bends). So we lost some electronics; not the GPS as it happened but it could easily have been.

So a sextant is part of our essential equipment, like the eye patch and the parrot.

The good news these days is GPS receivers are pretty redundant. Your chartplotter likely has an internal one. Many also have a networked GPS receiver (i.e. GPS24xd). If you have any tablets or phones they have their own GPS and can be disconnected from all power sources prior to entering lightning producing weather. If you have a smartwatch that is another GPS. Any DSC fixed radio has GPS. Even some handheld radios have GPS.

Long gone are the days of having a single very expensive GPS receiver on the boat.

That being said I agree having a sextant and compass is a good idea. Belt and suspenders.

[Stewie12]

Many years ago we were crossing the Atlantic and a lightening storm took out our mast head amplifier for our satnav. We navigated the rest of the way with a plastic sextant. We immediately bought a professional one. I would not cross an ocean without a sextant as the sun never fails.

[Colonel Bob]

Originally Posted by coopec43

I wonder how many yachtsmen use sextant navigation these days? Not many I guess. (But I've got a plastic one and I am dying to try it).

These days everyone is using satellite GPS however it has one huge drawback. What if an adversary destroys the system maybe by jamming the signal or "spoofing it" so that it positions you incorrectly?

It would be a big worry for navies and airlines so research has been taking place on "quantum navigation". If it become the way to navigate aircraft and ships around the world it will probably be just a matter of time before we do also?

There are actually multiple global positioning systems in orbit. The US launched the first GPS system satellite in 1984. GPS as a collective noun refers to the US system. GLONASS from Russia, Galileo from EU and BeiDou from China are on orbit. Modern phones track GPS, GLONASS and Galileo as a minimum. National attacks on other nations satellites is a very hostile act and counterproductive to own forces and international commerce in general. As the Ukraine war has shown, it is much cheaper, more clandestine and less provocative to do local terrestrial spoofing of receivers. The receive link margin is very slim and easily overpowered by cheap transmitters. This is why the ongoing research on alternative approaches is being pursued by the military.

[IanTrail]

Yes it’s true that every cruising boat today is festooned with GPSs in phones, tablets, plotters watches etc. Even in the event of a lightning strike you would be unlucky to loose them all. We keep our hand-held GPS in a biscuit tin, just in case.

[Statistical]

Originally Posted by Colonel Bob

There are actually multiple global positioning systems in orbit. The US launched the first GPS system satellite in 1984. GPS as a collective noun refers to the US system. GLONASS from Russia, Galileo from EU and BeiDou from China are on orbit. Modern phones track GPS, GLONASS and Galileo as a minimum. National attacks on other nations satellites is a very hostile act and counterproductive to own forces and international commerce in general. As the Ukraine war has shown, it is much cheaper, more clandestine and less provocative to do local terrestrial spoofing of receivers. The receive link margin is very slim and easily overpowered by cheap transmitters. This is why the ongoing research on alternative approaches is being pursued by the military.

Yeah the proper generic term would be GNSS. Most receivers these days are multi-constellation GNSS receivers. In fact many of the better ones are now multi-constellation and multi-frequency. Once L5 frequency goes live in or around 2027 (currently in "unhealthy" status due to insufficient L5 capable sats) expect a whole wave of new receivers to hit the market.

However kind of like bandaid and kleenex the predominant version has been used to incorrectly describe the category.

[Bill_Giles]

“People forget how limited sextants were. First it couldn’t be used n a cloudy day, 2nd you could only take one sight a day at noon, and third it was rarely more accurate than 20 miles. The sextant was a way to find land so you could follow the coast by compass and eye to your destination.” Obviously not a sextant user. One takes several sights, the noon one only gives latitude. The others use another Sun position, the Moon or the stars for longitude (and latitude too.).

Many experienced users can get as accurate as 5 miles. The question is ‘how accurate do you want to be?’ I’d suggest that one needs to be able to avoid bumping into land. When nearing land one keeps a look out

[JordanH]

So the premise is that the 5 GNSS systems will all be disrupted, the earth plunged into chaos and that it will be cloudy... and we still want to continue to navigate on our sailing cruise? I'm sure if the world is plunged that heavily into chaos, we may have other concerns on our mind.


I think, perhaps, a more practical solution would be to purchase a couple devices from various GNSS systems rather than invest in a quantum navigation tool for your cruising sailboat... We all should have a few different methods of navigation; visual navigation, compass navigation (Dead reckoning), celestial, GPS... why not just add a Galileo device to the mix? More layers of navigation gives more confidence.


FWIW, I know a company that is using the US military TALIN devices in their custom robots. They rewrote some of the navigation math because they operate in environments that are not able to receive GPS signals and are able to map out something like 10km's while being less than 10cm off of their accurate point. This is what some fighter jets use to help mitigate the risk of GPS being disrupted. I suspect that is more than sufficient, and quite a bit cheaper, than quantum navigation ; I suspect you'd be able to sail with reasonable accuracy for a month or more using that tech before it is out of whack. By then, you'd be to shore and wondering why the aliens wiped out 5 GNSS systems and have taken over the earth.

[gilligansail]

I have a plastic sextant as a backup. On my passages I do noonsites and compare to GPS. I can get within 10-20 miles of my GPS location. Noon sites are super simple all you need is a watch, a simple formula and the sextant. I kept it in my ditch bag.

[Statistical]

Originally Posted by JordanH

So the premise is that the 5 GNSS systems will all be disrupted, the earth plunged into chaos and that it will be cloudy... and we still want to continue to navigate on our sailing cruise? I'm sure if the world is plunged that heavily into chaos, we may have other concerns on our mind.

I agree. Very likely an attack on US GPS network is part of a coordinated first strike against US military assets that almost certainly involves nuclear intentions. Even if it isn't it may be mistaken as such lead to a US preemptively launching a nuclear strike while it still can.

There are a lot of things I worry about when sailing someone wiping out the GPS network is not one of them.

I think, perhaps, a more practical solution would be to purchase a couple devices from various GNSS systems rather than invest in a quantum navigation tool for your cruising sailboat... We all should have a few different methods of navigation; visual navigation, compass navigation (Dead reckoning), celestial, GPS... why not just add a Galileo device to the mix? More layers of navigation gives more confidence.

In fact most people probably already do. While we call them "GPS receivers" the reality is that for the past decade or so most "GPS receivers" are actually multi-constellation GNSS receivers.

The pretty common GPS 24xd for example tracks sats across four constellations (GPS, Galileo, Glonass, and BieDeu).

[lestersails]

Originally Posted by K_V_B

I doubt that this is your GPS being inaccurate. The maps are probably off. A lot of errors in maps are being discovered thanks to GPS. And you may have the wrong datum set etc...

I don't know about 15 miles, but 25-50 meters yes. I clearly recall the GPS being shifted about that amount on an approach to Sprat Bay on Peter Island. The GPS was going to direct me right onto the reef in front of the restaurant. Having studied the cruising guide and chart before entry and having good visibility, it was immediately obvious that the GPS was just wrong and I ignored it and navigated in by eye and the map. If it had been dark, I could have been totally screwed.
I really have no idea what was wrong as the next day when I turned on the nav system, it had me smack dab in the middle of the bay, spot on.

[searenity38]

Contrary to some of these comments, sextants can put you within a few miles of your actual location. Of course this has a lot to do with the proficiency of the navigator. Taking sights only at noon is a misunderstanding. Although noon sites are much easier to calculate, sights can be taken at any time, including night time.
There is a potential for foul play with our satellites. As proof of that, it's my understanding that the Naval Academy has reintroduced sextant training, so what does that tell you.
There are excellent educational sources available to learn celestial navigation. I like the one provided by the US Power Squadrons. I've taught their course a couple of times and learned so much in the process.
Taking sites while on a passage is a great way to kill some time.

[sailorladd]

When I set sail in 1986 from Cape Town SA, on my home built 31 footer, all I had to navigate was an old 1934 solid bronze sextant, a Timex quartz watch, paper charts, sight reductions tables, the current sea almanac and a pair of dividers and parallel rule... it was all I needed to get me virtually all around the world I would highly recommend it to any sailor!

[tjr818]

Originally Posted by MicHughV

What happened to:

"drive down this road until you see a red shed on the right side of the road, just past the red shed is a dirt road going to the left, take a left there and go about...hmmmm.....2miles or so, until you see a farmhouse with a green roof, just past that farmhouse is a road leading to your right, but it splits in two, take the left split and pretty soon you'll come to a cow pasture on your right, you can't miss this, as it's always full of cows, drive by this pasture and take the next turn to the right, that road will zig and zag a lot, but stay on it, and eventually you'll come to a river, follow that zig zag road for another mile...or maybe two until you see a bridge, relax, you are almost there, cross that bridge and about a mile...maybe two or three, you'll come to a store with a gas pump out front, the owner's name is Zeb, from there Zeb will tell you the rest of the way....."

That worked so well . . . until Zeb died.