When they send out a distress signal, they presumably give the GPS co-ordinates of where they are located to help the coastguard reach them more easily, and they won't be able to do that if GPS is jammed.
Following complaints from local fishermen, the Royal Navy has suspended satnav signal jamming during its ongoing Joint Warrior naval exercises, despite making every attempt to let people know. Locals around the Western Isles say the jamming of GPS has disrupted their lives, and put the safety (and profitability) of fishermen at …
Whilst you are technically correct, you are also quite a way away from the point. They can get your rough position through VHF, but they wont need to do that because you will know roughly where you are anyway (as all good skippers do). They will scramble the rescue craft and you will see it, you then fire your flares and bobs your granddad's son they find you, no GPS needed.
If you are in a position where a transponder needs to hit the water to activate and give off its GPS coords (think sinking or capsize where there isn't much chance of using the radio), then you are already fucked and by the time help gets to you the north sea will have made you an icecube.
M'aide M'aide, I have just come round after suffering a blow to the back of the head from a swinging Boom, I must have been drifting for hours and my GPS is not working. Oh and there's loads of blood coming out of the back of my head, can you find Wally?
Well, in that case you're in luck, 'cos the RN are running an exercise in the area, massively increasing your chances of being found, especially as they can triangulate your radio transmission very easily. Of course, if you were a mildly competent sailor then you'd just take a look at your chart, guesstimate drift over the period you think you were unconcious, and have a good enough idea of where you were likely to be in order to decide a rough course to steer for the mainland. Once you get close to the shore you'd be able to identify landmarks and find a safe harbour.
GPS and Distress calls
Although distress calls are (of course) transmitted in a vastly different part of the EM spectrum from GPS, disabling GPS disables a crucial part of the Global distress system (GMDSS). A VHF technology called DSC provides the capability to broadcast digital message containing latitude and longitude; these are used heavily in distress messages that are provided on pushing a Big Red Button. Of course, the latitude and longitude are normally provided by a GPS system; other types of electronic position finding are rarely used.
Automated distress beacons also provide positions from GPS; again, although the communications technology is not compromised, the GPS is. In this case, there is no alternative technology feasible.
However, the other side of the coin is that I, an amateur yachtsman who happens not to have gone to sea for a couple of months, knew all about these tests. I really don't understand why the fishermen didn't know about them - they are routinely notified through a wide variety of channels. What do the fishermen want? Personal visits from HRH?
North Sea ?
I think you'll find the North Sea is off the EAST coast of Scotland, and round most of the Western Isles is the ATLANTIC OCEAN . . . So if you're off the Western Isle and request a coastguard rescue to the North Sea, you are well and truly screwed . . .
Well, if you're such good friends with the coastguard that you can address them in the intimate voice, then they're probably already looking for you, non?
A DSC radio will keep transmitting a MayDay including the position once the button is pushed even if the crew are incapacitated.
Boats and GPS
Are they saying that if the GPS malfunctions on their boat they are screwed?
Maybe they need to dust off their compass and do it the old fashion way.
Good practise for them in case of such event.
Most fishermen can still navigate without GPS but in a similar way to how most people don't use a map in a car, most fishermen don't use charts now (but still have them onboard in case of failure).
GPS is used for net fishing close to the coast where the accuracy allows the boat to go closer to shore than you'd attempt without GPS.
From what I've heard - there's been outright GPS failure which means you just don't fish there and go for deep water fishing or back to port.
The real problem seems to be cases where the GPS is reporting inaccurate positions so you think you're safe and end up hitting rocks or catching nets - both of which appear to have happened during this exercise.
That made me think...
...that smartphones have an accurate clock, and a camera that you could use as a sextant. They also have a compass. Someone needs to make a Captain Pugwash locator app.
Android Market... IamAt
I think you might find something along those lines - using a digital camera as an emergency sextant - in The Lo Tech Navigator by Crowley combined with the excellent Emergency Navigation by Burch.
Problem is, a single sextant reading can only give you a line of position (long line drawn across your chart) and not a fix where two lines cross. Admittedly, if you can do that then it helps anyone searching you a lot as they only have to look up and down a line instead of hundreds of square miles of sea.
I was thinking of doing an solar navigation app for my Android, but hadn't thought of trying to combine it with the camera ...
"Most fishermen can still navigate without GPS but in a similar way to how most people don't use a map in a car, most fishermen don't use charts now (but still have them onboard in case of failure)."
I use a map. Less talking back to me than a silly GPS. ;)
"The real problem seems to be cases where the GPS is reporting inaccurate positions so you think you're safe and end up hitting rocks or catching nets - both of which appear to have happened during this exercise."
GPS is, first and foremost, a military system - civilian GPS was always a very nice afterthought. If the RN needs to jam it for practice twice a year, so long as they send out proper notice, the fisherman should simply cope. As for said notice, it's already been noted on this forum that amateurs who sail in that area were well aware of the coming failure - if the fisherman weren't paying attention to what should be standard notices, then that's their own fault. What are they going to complain about next, that the RN isn't nuking storms out of the sky so they keep fishing?
When I were a lad...
When I did my cert for offshore sailing, we were taught to use charts, tide tables, sextant etc. and one should never rely on the GPS, you would use it to check drift etc. between readings, but you only a fool would rely on the GPS, without plotting their actual course on the map.
I guess times are changing...
I gave up using GPS, when my system messed up and had me driving through the middle of Lake Constance, after I had been driving north for 2 hours from Munich! :-D
I still use Post-It notes when travelling somewhere, they are a lot more reliable and don't tend to go blank if the power fails :-P
Hi Mike, as you say, the sextant reading of the sun together with the time, gives you a line on the chart. Then a compass reading of the direction of the sun at the current time gives you an intercept on that line. I think!
As you say, as long as they send out the proper notices.
I live over 35 miles away from where the jamming was taking place (well outside of the range that the MoD specified as being affected by the jamming) and my GPS was giving positions about 10-15 meters from true.
So the notices that were issued were inaccurate to say the least.
The mind boggles ...
I used Loran briefly, when I operated a commercial salmon boat out of Noyo Harbor back in the mid 1970s ... I soon went back to charts & dead reckoning. I've fiddled with GPS, on and off, but charts and a compass are really where it's at when it comes to open water.
I spent some time living (and fishing) out of A' Chomraich when I was late teens/early twenties ... None of the fishermen I worked for even had a chart on board. One wonders how much of what makes us human that humans are going to lose thanks to so-called "convenience" ...
Using a boat eh? Back in my day I'd wade out and throw a net, as god, and our ancestors intended.
And I lived in a cave, Natures own palace we called it. Well not exactly, we had none of that fancy language you kids have now. But we lived better for the lack!
Oooh, a net! How fancy! Back when I was a lad, we would wade out and catch fish with our bare hands and then tear them open raw as the gods intended.
My family roamed the open plains, counting on our bearskins for warmth. Ever tried skinning a bear with your bare hands and curing the skin without fire? It ain't easy!
Don't worry - fishing boats powered by Java are coming. If you try to move your boat closer to the shore for better fishing, you will get an error message:
"The function 'MoveCloserTo Shore()' is deprecated. Please use 'MoveFurtherFromShore()' "
I think the commentards ...
... have underlined my point for me.
If you don't understand TheRealWorld[tm], you will make the same mistakes of generations before you ...
Emergency beacons have GPS
The mandatory marine 406 Mhz emergency location beacons transmit their GPS coordinates to let rescuers know where you are - as do commercial systems like SPOT
They can also work with no GPS at all
Initial location accuracy only to within a few kilometres though. GPS improves that to within a couple of hundred metres..
Although one would assume that should the coast guard receive a distress signal with no/an improbable GPS location, they, being fully aware of the activities going on, would be able to call up the RN (who they already cooperate closely with) and ask them to turn off the jamming for a bit so their GPS comes back up. This is assuming that the beacon doesn't also contain a homing signal.
Also I expect that the RN would be monitoring emergency bands in areas they are operating in, and may well already have a rough direction from one or two of the high tech communications rooms onboard the various ships (depending which ones were involved in the exercise) and probably wouldn't even need the coast guard to call them before they respond.
I'd suggest if your a commercial fisherman an ability to navigate without relying on GPS might be a good idea, in fact I'd be surprised if it wasn't a requirement of the license to drive a ship (when i got mine you weren't allowed to rely on GPS it was all visual and radar fixing).
It's not as if they're in the middle of the Atlantic these are coastal waters with the world's supply of distinct headlands to identify your position with. They don't even particularly need GPS to give their position when in distress either, radio direction finding having been perfected in World War 2...
How on earth did Cook, Columbus etc manage without GPS? I suppose fishing has only been possible since GPS became available?
Fools - how on earth did we manage to last thousands of years.
To be fair, when Cook et al were sailing, a lot of them didn't come back
These days we seem to expect something like five nines survival rate for mariners.
I know that's completely unreasonable, and we should go back to the good old days when ships came back 80% of the time, often with more than half the crew still on board!
And to be fair, the reason a lot of them didn't come back is because they were sailing a fragile ship the size of a modern trawler to the far side of the the world without the benefit of charts, because the land they were sailing to hadn't been charted *at all*, and hitting ground resulted in the ship falling apart. Add to that little things like scurvy etc. Unless i've missed something, none of those conditions are true for a modern trawler?
Given any IT bods understanding of the importance of backups, I think it's going to be a struggle to persuade most of us that the navigator on a ship shouldn't need to know how to read a map. Most scouts can manage that at 15 at a level that will let them get by, and i'm pretty certain I could chart my own position reasonably accurately with a map and compass simply by calculating the speed and thus distance travelled along a compass heading from my last position.
Cook et al were sailing, a lot of them didn't come back
But those were the ships that sailed too close to the edge of the world, where old charts had pictures if evil looking men and giant fish that ate ships..
Didn't Columbus arrive at the wrong continent? Wasn't he going to the East Indies? Perhaps GPS would've helped...
Mostly true, Peter
Hitting ground still causes ships to sink, steel not being naturally buoyant. While they fall apart less often, it's little solace to know that your submerged tomb is only in one or two pieces.
GPS will give you a location with errors measured in metres or tens of metres.
Taking a fix on known coastal features can give you a similar precision of fix, however it relies on good visibility (you need visibility of at least three coastal features) and tells you where you were a few minutes before.
Dead reckoning relies on a reliable fix to start you off, and your precision rapidly drops off - hundreds of metres within hours, several km within a tide. Hence trying to take a fix hourly.
- Dead reckoning on land is much easier because the land doesn't move under you at continually varying velocity.
The ancient mariners would take a fix using sun, moon and stars, and were often off by hundreds of km. Astromical fixes are not very precise and you can only take them at specific times of day - really local noon and midnight. (Sunrise/set and rise/set of chosen astronomical bodies are possible but you need big lookup tables and to be completely out of sight of land in perfect visibility for them to be useful.).
Off the coast of Scotland in autumn, how good do you think the visibility usually is to take those coastal fixes?
The Royal Navy have inertial navigation equipment capable of dead reckoning with the accuracy of GPS, given a good enough fix to start with. Civilians, less so.
Will they do this Galileo?
Can they? Also, there are some interesting documents about Galileo in the new Wikileaks archive, maybe an El Reg journo might like to take a look.
The Americans insisted on being able to selectively jam Galileo and the necessary arrangements have apparently been made to facilitate this. However, it is planned to use EGNOS (an extension to Galileo) for aircraft navigation around Europe. One wonders if the military will be so cavalier about jamming systems that will be used to fly and land aircraft.
Living on the isle of Lewis
There's normally an article in the local rag letting people know that an exercise is on it's way - this time they seem to have forgotten.
Normally the jamming isn't a problem as it shouldn't affect the Western Isles (as indicated in the map in your article) and fishermen just avoid the affected areas.
As mentioned in your article, the real worry from the fishermen is that DSC has failed (and well outside the areas specified by NATO). Although DSC does use a different frequency than GPS it stopped working which is worrying as it allows the coastguard to pinpoint the location.
On the island itself we've seen problems with GPS, mobiles (worse than usual), internet connectivity (due to a large percentage of the island using a wireless network) and satellite TV.
In general, a bit of a non-event for people living on the island but worrying for the fishermen especially since there's no emergency tug in the area anymore.
Think yourselves lucky...
When I lived up there they had regular "Spetsnaz attack" exercises. That was back when the airport runway got used for significantly heavier stuff than now ;)
While the idea of the RAF running all over the place "capturing" strategic sites such as petrol stations sounds amusing it is a monumental PITA when you live there.
It'd be nice if the RN would fuck off down south and run their exercises - I mean apart from Holy Loch they are exclusively based on the south coast of England. What the hell are they doing up here if their tactical base is the south coast?
People should note that the west coast of Scotland has LOTS of these poxy exercises (I'm sure Mr Page remembers where the sub captains qualified?) and that there is some irony/sarcasm above ;)
As I understand it GPS is supposed to be treated as a secondary navigation aid for exactly this reason - the military reserves the right to degrade or switch it off at any time, anywhere.
In practice mariners obviously aren't doing this, but perhaps they ought to dig out their sextants and Harrison chronometers and practice without GPS occasionally.
The US Military made a commitment to the United Nations in respect to intentional disruption of GPS at source, they committed to never doing it because GPS had become critical to so much of our lives.
As a side note:
I suspect that mobile and internet communications have been disrupted because many of them using GPS to discipline their frequency sources. The high accuracy 1PPS pulse from GPS is used to synchronise microwave relays as well as some fibre nodes. Most data centres should try to have a clock/frequency source which can sustain itself for a while in-case GPS is unavailable, but eventually that might drift and I am not sure if mobile base stations / telecoms relays contain such an expensive/accurate time source.
Local time sources
Generally if you buy a time appliance that provides a NTP stratum 1 source using GPS, MSF or DCF, then they put a high-precision temperature controlled clock in the appliance for just the situation where your exterior time source is not available.
Normally these are accurate to <2ms per day drift (this is for the entry level device from Time and Frequency Solutions Ltd. - other NTP time appliances are available), so will take over a year to drift even a second from real time if they lose their external feed. There are better ones if you need more accuracy.
So if you need accurate time, relying on a regular feed from GPS is just not necessary.
Of course, some people might be doing time synchronisation on the cheap, but that is then their problem.
"supposed to be treated as a secondary navigation aid"
This is a little disturbing as the new point-to-point flight system, as opposed to corridors, is predicated on using GPS because it is a single system, like the earlier Decca Navigator, as opposed to individual, multiple systems such as inertial or radar navigation.
I'd be very interested in knowing when they did this. I know that in a recent skermish, the US put in a number of fixed markers with known Lat/Long and turned off the GPS in the whole regon for a while. The only way of knowing where you were was using one of our inertial navigation platforms, and syncing the location at one of the known points. If you ever switched it off, it was screwed though; it could find true north after about 5 minutes, but apart from that it wouldn't know where it was.
will these exercises jam GLONASS and Galileo?
Since it seems to be jamming other satellite signals (such as TV) and mobile signals - I'd say yes.
Probably already does
They're pretty close, channel wise, to GPS.
Re: In future
GLONASS is Russian, so jamming it is going to *really* upset some people who have the ability to make their feelings known.
Galileo is a civilian system, so I'm sure that Brussels will not be happy if the military starts jamming it. Probably pass a Ero-lay making such jamming illegal!
Remember that they are not jamming a system or systems, just rendering the signals unusable over a patch of the earth. GLONASS really can't complain if their system is inoperable over north west Scotland and Galileo likewise, unless it is so frequent or extensive that it starts putting off paying (or potential paying) customers.
No more than the US was upset by this. As in not at all. And why should it?
What they all seem to have forgotten...
...is that GPS is first and foremost a military system. And it's not even our system, it's the yanks. It's only courtesy that they inform everyone about it.
As noted above - in mission-critical applcation, GPS should never be your primary navigation device.
Also...it's interesting the navy are conducting GPS-less maneuvers; obviously one of their anticipated attack vectors is complete destruction of the GPS network by their antagonist. And who has recent form with destroying satelites, I wonder...
To the 'why not use a map' comments
O.K., how about you having to revert to pagers for a bit?