GPS anxiety

Two chaps in a 10mt boat, longlining offshore. Set off for home, cup of tea, tin mug next to the compass. They ran out of fuel thirty miles up channel.
I used to get interesting course changes when I dragged the large chain end weight along the deck above the autopilot compass.
 
My sailing, of the semi adventureous coastal type is mostly reading, noting down and memorising the offshore hazards/races/rocks, avoiding them and then keeping the land on the left, or the right, depending on which way I am going. When going further offshore, Cherbourg, Cork, Kilmore Quay, Arklow perhaps, the plotter is obviously on, but I would have no qualms about finding my way without it.

My first Solo Channel crossing, no plotter or GPS, had my mate Tim saying as dawn broke " You jammy bugger!!! That is Braye Harbour dead on the nose!!!"

And it was. :)
 
lustyd said:
Looking at the FAQ that site appears to be almost pure speculation.
Click to expand...
It’s based on data reported automatically by airliners. More flights through an area obviously makes for better quality data. But in this case the news stories also mentioned separate reporting of GNSS problems in that area by Finnair pilots.
 
fisherman said:
Two chaps in a 10mt boat, longlining offshore. Set off for home, cup of tea, tin mug next to the compass. They ran out of fuel thirty miles up channel.
I used to get interesting course changes when I dragged the large chain end weight along the deck above the autopilot compass.
Click to expand...
Oh, we’ve had that too! The autopilot compass is under one of the saloon settees. Once my co-skipper put the MacBook down near it while taking a break from work, and the autopilot did an immediate 40 degree turn. Luckily was easy to catch quickly, as we were sailing down a pretty narrow and rocky fairway on the east coast of Sweden.
 
bergie said:
It’s based on data reported automatically by airliners. More flights through an area obviously makes for better quality data. But in this case the news stories also mentioned separate reporting of GNSS problems in that area by Finnair pilots.
Click to expand...
Yes it said the source in the FAQ. Completely speculative, there are many reasons, including altitude that might cause an airliner to have poor GNSS reception. Poor reception can mean literally anything from loss of one satellite to full position loss. The site seems desperate to draw some conclusion about GPS jamming from such a poor set of data, despite that being the absolute least likely cause over such a wide area. The data isn't even entirely drawn from GNSS systems!

If you're wanting to make conclusions about GPS jamming I suggest using a more robust source, that one is a complete joke.
 
lustyd said:
Looking at the FAQ that site appears to be almost pure speculation.
Click to expand...

If it is also including INS - then its useless ... as INS requires updates to remove accumulated errors between such positional updates.

My Father was involved in bringing INS to Commercial Aircraft ... Senior Flight Ops, UK DoT CAA. In fact he did the trans polar flight with BOAC that opened up that route - I have his handheld manual plotters used on that flight.
He later was part of the Committee overseeing commissioning of Concorde .. and its navigation.
 
Sorry to burst your bubble but it is using mode s extended squitter transmitted by the aircraft which gives a navigation uncertainty value to the transmitted position (version 0, version 1 gives both an accuracy and integrity value). This is calculated by the aircraft. There is no reason to doubt the website even if it smells like a conspiracy nutter. The data is freely available online.
 
Have a read of the website, there’s plenty of reason to doubt and assume it’s a conspiracy nutter. They don’t even quantify poor position, if GPS were being jammed it would be being jammed, not slightly degraded. They also don’t cross reference type of craft or position or even weather. The site appears designed to suggest GPS is being jammed, not to genuinely investigate signal quality.
 
lustyd said:
Have a read of the website, there’s plenty of reason to doubt and assume it’s a conspiracy nutter. They don’t even quantify poor position, if GPS were being jammed it would be being jammed, not slightly degraded. They also don’t cross reference type of craft or position or even weather. The site appears designed to suggest GPS is being jammed, not to genuinely investigate signal quality.
Click to expand...
GPS degradation is an accepted form of 'jamming / interference' ...

Have worked as Contractor with Military in two war zones ... and that was common practice.
 

From the FAQ:​

​

'Does red and yellow always mean there's jamming?​


No. Red and yellow hexes show where a significant number of aircraft reported low navigation accuracy. This often seems to be in regions where it's known or suspected that GPS jamming is occurring, but the data doesn't tell me what's causing the low accuracy'


Ok so here is a representation of data, and comments over possible causes. The data could be better defined to promote understanding. However the quote above shows it to be a long way from being 'a conspiracy nutter'.
 
This thread had me digging out my old Davis Mk 15 sextant. It got me across the Atlantic 30 years ago. Though I did buy an early Magellan GPS in the USA to get back.

It's sat unloved in the back of a cupboard for 20 years. Nevertheless on checking today: parallax error - nil; side error - nil; index error - 0.4' off. Not bad for an instrument once denigrated as a pile of plastic junk. But the foam padding in its storage box had turned to dust.
 
Airscrew said:
The original question was re anxiety, and whilst it doesnt make me anxious, this article today clearly shows that we should never be 100% reliant, nor 100% confident, on GPS alone.

Russia suspected of 63-hour attack on GPS signals in the Baltic region
Click to expand...

I live on west coast of Latvia .... and use GPS every day ... unless the Russian disruption is targetted and small area aimed - I have seen no disruption whatsoever and no-one I know shipping / yachting etc this side of Baltic has mentioned anything about it ...

Of course Russia and West have electronic capability to swamp or block ...
 
Anyone with 5 bucks worth of electronics has the capability to block GPS, it’s a very weak signal.
The question is why they’d bother. Neither side needs GPS to be functional for anything bigger than a drone so they’d only really achieve annoying civilians.
 
lustyd said:
Anyone with 5 bucks worth of electronics has the capability to block GPS, it’s a very weak signal.
The question is why they’d bother. Neither side needs GPS to be functional for anything bigger than a drone so they’d only really achieve annoying civilians.
Click to expand...
Surely somebody has shown considerable delight in "annoying" civillians so far. I assume & I stress, asssume, that ferries & the like use GPS. Should one get into difficulties, due to a sudden unexpected disruption in the signal, before the navigator could correct the situation, that would cause mayhem. Likewise, a tanker sinking causing an evironmental disaster would not worry Vlad the Invader one jot. But it would tie up resources. Particularly with the "grey" shipping passing in Danish waters without authorised pilots, if one caused an oil spill.
 
You must log in or register to reply here.

Share this page

Top