GPS anxiety

[Sandy]

9 axis compass

Can you explain what a nine axis compass is?

Just looked at the price of a Garmin fēnix® 7! I am pretty sure I've never spent that amount on watched in my whole 61¾ years! A cheap WaveCeptor* watch does me.

* WaveCeptor watches are corrected daily via a radio transmission.

 

[lustyd]

Fog will not knock out your depth sounder

It would be a very unlikely scenario that causes loss of GPS on all devices but not loss of depth on a modern boat. If anything you’re more likely to lose depth than position since a mobile can’t do depth.

 

[lustyd]

Can you explain what a nine axis compass is?

It’s just what the chips are called. 3 axis (x,y and z) for compass, accelerometer and rotation making 9 readings in total which can be used together for all sorts of cleverness. On boats they will show pitching, wave height, heel etc. on a watch it can tell me what stroke I’m doing while swimming or how much bounce I have when running. It can even measure pace when running just with wrist movements.

 

[GHA]

Can you explain what a nine axis compass is?

One of these.
ICM20948 9DoF Motion Sensor Breakout
https://invensense.tdk.com/wp-content/uploads/2016/06/DS-000189-ICM-20948-v1.3.pdf

The raspberry pi based Pypilot autopilot uses a 9dof sensor reading 10 times per second.

Raymarine charge 500 quid for theirs istr.

 

[Refueler]

Can you explain what a nine axis compass is?

Just looked at the price of a Garmin fēnix® 7! I am pretty sure I've never spent that amount on watched in my whole 61¾ years! A cheap WaveCeptor* watch does me.

* WaveCeptor watches are corrected daily via a radio transmission.

Just a comment ....

I have sailed on ships that had electronic Chronometers - which could be corrected by radio signals .... but ALL were disconnected from such service for specific reason ...

You have no idea of the Chron's daily error. If you lose that Radio signal - then how do you know the correction for the time when doing sights ?? OK - 99% or more of people on here are not going to be that worried ..... or doing sights anyway ..

But its a valid point.

 

[Graham_Wright]

Whilst it’s possible you may lose the gps signal and therefore your position data, you will still have the charts available on your MFD/plotter so no pressing need to carry paper charts albeit paper charts are easier to use than a digital on screen version.

Not if the reason you lost GPS was that you lost all electrical power.

 

[Chiara’s slave]

I had thought that most of the forum was old enough to have navigated pre GPS, or else when it was expensive and rare. Why the fuss? Have we all just gone soft?

 

[ShinyShoe]

But don't forget that US GPS is not only system and many sat gear today can pick up more than just US sats ...

There seem to be a few scenarios in different people's heads - each of which may differ...

1. A rogue state (aka Russia) - either disabling the system or, maybe worse, spoofing the results to make you believe you are some place else
2. Our own state doing something similar, perhaps to confuse some inbound, actual or imagined, missile
3. Our own state testing its ability to do #2 (which comes with warning)
4. A technical loss of functionality at the satellite end
5. A technical problem on board

1-3 are likely to be aimed at interfering with ALL systems not just the US GPS.

4 seems bad luck if it takes out them all, but I guess some of the solar flare stuff might

5 seems the most common, and with modern tech as people have commented you can have back up systems on a phone. Etc.

It's worth thinking about. Earlier this year i picked up, on the Navtex, that the navy was going to be practising gps jamming from a spot with a 20 mile radius. Basically portpatrick. I am sure it will have been advertised elsewhere but I wouldn't have known. They did say they wouldn't do it if conditions were not good for trad nav.

It would also be broadcast on VHF

From an AI

Is this how forum posts work now?

What AI doesn't tell you is what happens if it goes down. Is it an instant meltdown (seems unlikely) or do these devices all have their own onboard clock and simply synchronise to the sat clock when they need to.

"Degraded call quality" hardly sounds like Armageddon! If I move money and need my transaction timing to be perfect to buy and sell I'm sure it matters... But will the world actually collapse? Doubt it.

Does AIS just use GPS? My plotter is trilingual, I believe. To think that all 3 would go down at once is beyond thinking about. But, there's always a paper chart, and old fashioned chart gear on board. I’d worry far more about electrical failure than GPS failure.

It's concerning that you've not considered the possibility of loss of the system (see #5). But so so so much of this worries me - AIS is hardly an essential tool to routine navigation. Useful - yes, essential - no.

You are (a) reliant on the info sent from the other end [is it being spoofed? Monolingual etc], (b) only getting data from big enough craft and a selection of others. (c) no military shipping. Overall it's half a picture at best...

To me the OPs question is far to broad.

Crossing an ocean... Some fix on paper seems logical because if something goes very wrong you might need a rough "where am I". How often... I suspect if you are less than >24hours from land and on a straight course... not too often.

The closer you get to land the bigger the risk, and likewise the greater the chance you don't have time to fix issues

Then once insight of land, provided you have a (backup) chart (paper or electronic) the need probably diminishes again.

Add to that the places you sail... If you like nudging your way up the Baltic to visit Crimea... You probably need a significant plan for your nav. (Oh and a bullet proof boat).

If you are pootling on the South of England in sight of land... Chance of a rogue state seems low, but even if they did your ability to nav by eye should fix that...

 

[Chiara’s slave]

You’ve misunderstood my angle. I don’t have AIS. I wS merely pointing out that it can have, likd other sat nav based systems, multiple position finding systems. And I’ the main protagonist suggesting that total on board failure is the most likely scenario. I’m therefore not the least concerned.I’m just prepared.

 

[lustyd]

Just a comment ....

I have sailed on ships that had electronic Chronometers - which could be corrected by radio signals .... but ALL were disconnected from such service for specific reason ...

You have no idea of the Chron's daily error. If you lose that Radio signal - then how do you know the correction for the time when doing sights ?? OK - 99% or more of people on here are not going to be that worried ..... or doing sights anyway ..

But its a valid point.

All of the time sources on my boat apart from the decorative brass clock use live GPS time so corrections are irrelevant. RTCs don’t suffer noticeable drift these days anyway even if they did disconnect for a few minutes.
I guess if my hobby was taking sights I’d also have an old chronometer on board to add to the fun.

 

[Refueler]

I asked on a ship a while back ... what would you do if GPS stopped working and all other sat systems were out ?

Answer : Get a shore job !!!

I asked what about the Sextant ?? They did not know which cupboard it was in ... eventually I found it with the Master locked away !! I asked where is 2nd ?? Nobody knew !!

 

[Refueler]

All of the time sources on my boat apart from the decorative brass clock use live GPS time so corrections are irrelevant. RTCs don’t suffer noticeable drift these days anyway even if they did disconnect for a few minutes.
I guess if my hobby was taking sights I’d also have an old chronometer on board to add to the fun.

Minutes ???? Think you missed the whole point ... I'm talking DAYS ..... even weeks ....

A ship voyage can be more than a month ...

As to your live GPS time .... isn't that one of the first that will go when system stops ?????

 

[dunedin]

Not if the reason you lost GPS was that you lost all electrical power.

But with most people carrying lots of mobile devices with GPS, and most of us have charts on some of them also, ships power failure should not result in loss of a GPS position (if it does you have failed to prepare). The real issue is if the GNSS signals are blocked or stopped by an external event.

 

[lustyd]

Minutes ???? Think you missed the whole point ... I'm talking DAYS ..... even weeks ....

A ship voyage can be more than a month ...

As to your live GPS time .... isn't that one of the first that will go when system stops ?????

The Kraken will get us long before GNSS fails. Just not a risk worth planning for.

 

[Refueler]

The Kraken will get us long before GNSS fails. Just not a risk worth planning for.

Me - I'm quite happy to work with or without GPS ... I was trained as a Ships Navigator before Satnav came on board ...

 

[lustyd]

Me - I'm quite happy to work with or without GPS ... I was trained as a Ships Navigator before Satnav came on board ...

I’m happy to work either way too. In practice I use GNSS and plan for reasonable problems. I don’t plan for unreasonable fairy tale scenarios.

 

[jwilson]

I have lost GPS several times. First time in early 1990s when GPS itself was a fairly new thing and I took a "waterproof" Garmin GPS45 on a long passage as a backup to sextant and tables and two Casio digital watches. Turned out not to be that waterproof, but after dismantling and drying out in a low oven it worked again for a while (the boat leaked- quite a lot).

Several times more recently have had total GPS blackouts in areas where foreign warships and bases were near. Not just one GPS dead, on one occasion had four on board: all lost position.

 

[lustyd]

But let’s not forget that Columbus managed to find the Americas not only without a chart but before longitude could be measured. Other people managed to repeat this feat for hundreds of years before the chronometer came along.
If accurate navigation fails, inaccurate navigation will get you home safely in all but the most unusual circumstances.

 

[johnalison]

But let’s not forget that Columbus managed to find the Americas not only without a chart but before longitude could be measured. Other people managed to repeat this feat for hundreds of years before the chronometer came along.
If accurate navigation fails, inaccurate navigation will get you home safely in all but the most unusual circumstances.

As Sir Cloudesley Shovell can testify.

 

[Refueler]

But let’s not forget that Columbus managed to find the Americas not only without a chart but before longitude could be measured. Other people managed to repeat this feat for hundreds of years before the chronometer came along.
If accurate navigation fails, inaccurate navigation will get you home safely in all but the most unusual circumstances.

Just to split hairs ....

Columbus did not actually find America ... he landed on an island - which one is still in dispute ! But its plain that he did not reach the mainland.

Longitude was not really an issue as long as navigator played the game of not aiming for the destination - but upwind of it ... He relied on the Latitude far more ...
In old days - of course they used Lunar tables to try and get round the Longitude mess ... glad that got binned !!