GPS anxiety

[Refueler]

Heavily utilises, yes. Relies? Technically no.

It's certainly built around the idea of having continuous satellite positioning, but remains usable even in the absence of it. If you lose GPS because a wiring connection corroded through, or you're sailing in an area with jamming, or even if it's working fine but the chart was using an incorrect datum, you can still use the ECDIS (or really any decent ECS system) for navigation. No need to haul out paper.

But, as someone mentioned above, there isn't customer demand for such features even though they are quite simple to implement.

Its positional operation relies on GPS / GLONASS / GALILEO / BEIDOU or whatever sat system opted for.

Once Sat data stops - it becomes a fancy chart display ..... I never said it was not useable - in fact I added :

The only answer is to create / install a completely different system that does not use sats ... but how long before an adversary jams / spoofs that ? Its fine if near enough to coast to use radar or closer and use mk1 eyeball / compass ... offshore to return to using Sextants ....
Blimey that'll cause a stir ... I now have a vision of all those young 3rd / 2nd mates rushing off to learn to use a sextant !!

Because that is the reality ... to relegate the ECDIS to a scrolling chart display ...

Even my old Lowrance plotter ... my smartphone ... my tablets and Garmin UHD displays can all act as chart displays ...

My post was due to your post implied ECDIS was capable of some wizardry if GPS fails ...

 

[requiem]

Because that is the reality ... to relegate the ECDIS to a scrolling chart display ...

Even my old Lowrance plotter ... my smartphone ... my tablets and Garmin UHD displays can all act as chart displays ...

My post was due to your post implied ECDIS was capable of some wizardry if GPS fails ...

Not some wizardry, simply sufficient to replace paper. That's the effective distinction between plotters and ECDIS/ECS; your plotter is largely a passive "chart display" if it loses position. ECDIS/ECS allow continued navigation, either via dead reckoning mode (which I reckon is would be over-engineering things for the leisure crowd) or simply manually plotting fixes on the screen.

 

[Refueler]

Not some wizardry, simply sufficient to replace paper. That's the effective distinction between plotters and ECDIS/ECS; your plotter is largely a passive "chart display" if it loses position. ECDIS/ECS allow continued navigation, either via dead reckoning mode (which I reckon is would be over-engineering things for the leisure crowd) or simply manually plotting fixes on the screen.

I can do all those on my tablets .. phone ... Garmin ... and my old Lowrance !!

My PC charting has DR / EP function as well ...

In fact I can turn off GPS input and use as a chart only .....

 

[lustyd]

When people say that one should not sail in certain conditions that is a crap comment. I have, many times, started off in 15MPH winds (also forecasted) & been confronted with considerably more when half way through the trip. If one is half way between Bradwell & Ramsgate & things kick up then there is not a lot of choice to sail elsewhere.
Does danger come from personal choice. Of course it does. We should all stay at home. Thanks for the advice on that one.

I didn't say don't sail in bad conditions at all, I said that in those circumstances don't carry on with your original plans.

Bradwell to Ramsgate. You're halfway and GPS fails. You can see on the chart that there is a windfarm to your port and a whole bunch of buoys and that Ramsgate has some fairly dodgy bits. Turn the boat around so the windfarms/buoys are on your starboard and you're sailing away from said dodgy bits. Stay far enough out that you're over 20m contour but not so far out that you hit a windmill. At this point you're safe and know well enough where you are to get home. Sail north for a few hours, basing your progress on time since passing a given buoy and you'll know roughly when you're back at Bradwell entrance then start looking for buoyage to follow in. There appears to be plenty of depth on the approach for a yacht and lots of buoys to identify to find your position approximately enough to put a finger on the screen and see what's coming next.

When I spoke of personal choice, it was not on the decision to go sailing, it was your dogged determination not to change your plans or destination - this has killed a lot more sailors than GPS failure.

 

[lustyd]

Also, while not relevant to sailing, it is noteworthy that in urban canyons such as those of Hong Kong, the accuracy of GPS is often significantly degraded by multi-path and shadowing effects. I observed this most recently a couple of months ago when the accuracy would go from tens of metres to hundreds of meters depending on the location

Get a more modern device. My wrist watch has multi-band and multi-GNSS and is excellent in urban canyon situations. It's usually in the ~1m range for accuracy and I don't think it's ever been 10m out despite my best efforts.

In general, I agree that buoyage is a good guide, but not always. In rapidly changing areas such as the East Coast, buoys can either drag or be misleading because the bottom has changed since they were last positioned

My point was that in an emergency you should be making better decisions. The yacht is safe until you choose to try your luck. If you know one place has issues, sail to somewhere else if there's a navigation emergency or put the anchor down until you have a better option. I never said I could navigate anywhere on the planet with no GPS or position, I said that with the chart on the plotter screen I could get the yacht to a safe haven, probably from anywhere in the world if it had provisioning for the trip. Knowing your exact position and being able to get to safety are not the same thing, refueller's story showed that well - they were unsure of position so took actions to mitigate that uncertainty until they were safe.

 

[requiem]

I can do all those on my tablets .. phone ... Garmin ... and my old Lowrance !!

Same here, it does depend on the app/hardware you use. I think many are less capable and simply turn into "scrolling chart displays"

 

[lustyd]

I think many are less capable

I think this applies to the users at least as much as the devices!

 

[AntarcticPilot]

Get a more modern device. My wrist watch has multi-band and multi-GNSS and is excellent in urban canyon situations. It's usually in the ~1m range for accuracy and I don't think it's ever been 10m out despite my best efforts.
.

My device was top of the range about a year ago. If you're getting better accuracy than I in a place like Hong Kong, your device is using techniques other than GPS to improve the positioning. I note that all my Hong Kong friends and relations see exactly the same sort of thing - and I have lots of friends and relations there!

 

[st599]

mmmmm just reading your post and sitting here trying to figure out your point ...

ECDIS relies on GPS ... Full Stop.

It usually integrates Radar / ARPA ... AIS .... :



Where will the position info come from for the ECDIS system ?

The RIN/MCA/RYA paper suggests the reason that chartplotters have a "Not for Navigation" splash screen and are not accepted by the MCA is that they can only accept position data from GNSS/GPS whereas ECDIS is allowed as you can input a position using traditional navigation techniques such as a 3 point fix. So they're suggesting that for the post paper chart world, chartplotters will need to accept location input data from more traditional techniques and from Radar.

https://cdn.ymaws.com/rin.org.uk/re...s/smallcraft/Proposal_for_EN_system_Rev6_.pdf

 

[st599]

In fact I can turn off GPS input and use as a chart only .....

Which isn't enough for the MCA - they want the software to calculate where you are from otherfixes (3 pt, running etc.) then use that info as if it were a GPS fix.

 

[lustyd]

My device was top of the range about a year ago. If you're getting better accuracy than I in a place like Hong Kong, your device is using techniques other than GPS to improve the positioning. I note that all my Hong Kong friends and relations see exactly the same sort of thing - and I have lots of friends and relations there!

Age of the device doesn’t matter. Does it have multiband? That’s the crucial part in urban canyons as it uses multiple frequencies to deal with the reflection of signals and multi-GNSS gives access to more satellites which can help too. Most devices don’t yet have this, the top end Garmin being exceptions and relatively early adopters to the tech. Their handhelds like the gpsmap with better antennas help here too.

 

[B27]

.....

I disagree that paper charts are a must in most of the world cruising grounds. They are nice to have, but a must is stretching things. In the vast majority of places there is buoyage, and even without buoyage there's usually enough visual information to dead reckon your way to somewhere safe. From a safety perspective, you don't need precision, you just need to avoid danger and that doesn't require plotting anything on the chart. We all learn this with pilotage notes - keep the lighthouse to port and you'll be safe or keep these things in transit and you're safe, keep the depth over 20m until you can see into the harbour clearly etc.

You need the knowledge of what pilotage features or whatever you're going to use.
That could be stored as a sequence of instructions, leave the buoy to port, head 300 degrees until the transit, follow the transit...

Or it can be stored pictorially in a paper chart format, or pilot book could mix the two.
Or it can simply be in your head as knowing the route in and out of a e.g. few Solent ports and where they are and what they look like.

Or it can be stored as electronic charts .


You can live without paper charts if you have Navionics or whatever, even without GPS working.

Yes there are channels you can follow just buoy-hopping with no knowledge, but most of us aspire to more than that.


Paper charts and a GPS giving lat/long used to work for us last century.
Nothing to stop you using electronic charts and e.g. a hand bearing compass to create a position line. Or a depth sounder or simply reading the name of f the buoy and using the compass to find the next one.

 

[bergie]

So here was an interesting one: we're currently anchored off Lanzarote. Two nights ago, our anchor alarm went off. Basically no wind (2-3kt said our system).

Chartplotter and Signal K anchor alarm are both showing us dragging at about 2kt to the sea.
Transits to various shore features were stable, however. And anchor chain and snubber felt completely normal.

Ten minutes later, we magically "dragged back" into our original swing radius, again at about 2kt speed.

Investigating it afterwards, I saw from Signal K logs that the system had switched to our secondary GNSS receiver at that time. The primary is set GPS-only, while the secondary also uses the other constellations. And apparently the primary had lost the fix.

While we were on deck looking at transits, the skipper of the charter boat anchored next to us also started pointing his searchlight around quite frantically. So that makes me think they also had an alarm go off. So that would very strongly suggest a GPS glitch instead of something wrong in our end.

Now, some GPS drift is quite normal. But this was the first time I've seen something this drastic.

 

[zoidberg]

Most military vessels - and many aircraft - have GPS 'spoofing' equipment fitted.... something RIN warned about multiple times. There's a fair likelihood some matelot had a routine test to do, perhaps after a Black Box swop-out, for a few minutes which happened to affect your anchorage briefly.

 

[finestgreen]

Nothing that flightradar picked up from aircraft ADSB data:

Live Flight Tracker - Real-Time Flight Tracker Map | Flightradar24

 

[Irish Rover]

New global navigation data service launched in Ireland