GPS users must plan for outages
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GPS users must plan for outages
GPS users must plan for outages
Satellite woes mean that plan B is a must
Firms that rely on the US Global Positioning System (GPS) should ensure that they have a fallback plan, as one of the UK's top navigation experts has warned that the system may prove unreliable.
Speaking at a Cambridge University conference in September, Norman Bonnor, a retired RAF Air Commodore and president of the Royal Institute of Navigation, said the GPS signal is more fragile than many users might suppose. "Too many people don't understand its foibles and vulnerabilities," he added.
GPS is widely used in systems ranging from car navigation to emergency services co-ordination; and for time-keep- ing in utilities, finance and telecoms sectors.
The system relies on a network of satellites, which cannot be repaired once launched and have a limited lifespan. Sixteen of the present 28 satellites were built to last seven and a half years, but are now between eight and 14 years old. Twenty-four satellites are required for full coverage.
Bonnor said launches of new satellites are "only just keeping up" with current losses of around two satellites per year. But the failures could accelerate due to the number of satellites that have used up their redundant hardware. "Many are on their last legs," he explained.
The first of eight modernised satellites, built to last 10 years, was due to launch yesterday after a series of delays. A European alternative to GPS, called Galileo, is not expected to be complete until 2010.
Lem Bingley, IT Week 27 Sep 2005
Satellite woes mean that plan B is a must
Firms that rely on the US Global Positioning System (GPS) should ensure that they have a fallback plan, as one of the UK's top navigation experts has warned that the system may prove unreliable.
Speaking at a Cambridge University conference in September, Norman Bonnor, a retired RAF Air Commodore and president of the Royal Institute of Navigation, said the GPS signal is more fragile than many users might suppose. "Too many people don't understand its foibles and vulnerabilities," he added.
GPS is widely used in systems ranging from car navigation to emergency services co-ordination; and for time-keep- ing in utilities, finance and telecoms sectors.
The system relies on a network of satellites, which cannot be repaired once launched and have a limited lifespan. Sixteen of the present 28 satellites were built to last seven and a half years, but are now between eight and 14 years old. Twenty-four satellites are required for full coverage.
Bonnor said launches of new satellites are "only just keeping up" with current losses of around two satellites per year. But the failures could accelerate due to the number of satellites that have used up their redundant hardware. "Many are on their last legs," he explained.
The first of eight modernised satellites, built to last 10 years, was due to launch yesterday after a series of delays. A European alternative to GPS, called Galileo, is not expected to be complete until 2010.
Lem Bingley, IT Week 27 Sep 2005
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Well what a coincidence! Europes' own system is on its final hurdle and here we have a retired curly tash rubbishing to US system which has served us all proud.
I wouldn't read too much into it, replacing a satellite is expensive but it's not much a problem.
Don't throw away your Tom Tom yet mate
I wouldn't read too much into it, replacing a satellite is expensive but it's not much a problem.
Don't throw away your Tom Tom yet mate
To be fair to Mr. Bonnor, ISTR he is a former President/Chairman of the Royal Institute of Navigation, and well-respected.
One could also argue that the GPS space segment has proved to be remarkably robust, and the Block III replacement programme may have an even longer life....
One could also argue that the GPS space segment has proved to be remarkably robust, and the Block III replacement programme may have an even longer life....
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AFAIK GPS outages are predictable and are promulgated by AIS notams as likely to affect certain airfields between specific times on specific dates as a function of satellite coverage, maintenance downtime etc.
Not being able to rely on GPS and to have a backup plan sounds eminently sensible in aviation to me. After all we don't plan on all engines, generators, hyd systems, etc working on board nor on the wx being fine nor the CAT3 ILS being available when flight planning.
GPS availability (or lack thereof) is just another part of the planning process, imho.
The US still have the ability to put an uncertainty factor into the GPS accuracy in times of need anyway, wouldn't that render GPS approaches invalid/unusable.
He may have a curly 'tach, but is he actually saying anything new?
Not being able to rely on GPS and to have a backup plan sounds eminently sensible in aviation to me. After all we don't plan on all engines, generators, hyd systems, etc working on board nor on the wx being fine nor the CAT3 ILS being available when flight planning.
GPS availability (or lack thereof) is just another part of the planning process, imho.
The US still have the ability to put an uncertainty factor into the GPS accuracy in times of need anyway, wouldn't that render GPS approaches invalid/unusable.
He may have a curly 'tach, but is he actually saying anything new?
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Another reason why a backup might be needed. A couple of weeks ago a NOTAM was issued warning of GPS jamming trials taking place in Wales.
The jamming WAS succesful - we saw it first hand, the system can be rendered useless. Our FMS warned us that it was receiving NO satellites for quite some distance as we flew over Wales. Thankfully it also receives DMEs so the accuracy was still acceptable.
The jamming WAS succesful - we saw it first hand, the system can be rendered useless. Our FMS warned us that it was receiving NO satellites for quite some distance as we flew over Wales. Thankfully it also receives DMEs so the accuracy was still acceptable.
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Navigating with a secondary system is good practice and has been for centuries. There's not much effort involved in running a raw data cross check against an old fashioned paper map at regular intervals. How else can you be absolutely certain that your FMS is telling the truth?
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Great to know that if my highly reliable GPS which has never failed me in years - or ever for that matter - is switched off by the Americans, or just plain fails, I can use an NDB to precisely fly through thunderstorms etc.
What a joke! The GPS has proved itself to be a real boon to navigation, and I am amazed eminent people, including CAA folk, keep on about how potentially unreliable it is. Surely all our aids are potentially unreliable, and none of us would hang our lives on one aid.
As for the US shutting it down, this is not likely to happen without notice, as there are thousands of aircraft in American airspace using GPS, nearly all as their primary aid, and the US wouldn't forget that.
As for the requirement to still have an ADF and DME fitted in UK airspace if one wishes to fly airways - why? GPS can deal with both far easier. OK, if one is going to make use of an NDB as an approach aid, that is fair enough, but there ain't so many of these around now. Could someone please tell the CAA?
What a joke! The GPS has proved itself to be a real boon to navigation, and I am amazed eminent people, including CAA folk, keep on about how potentially unreliable it is. Surely all our aids are potentially unreliable, and none of us would hang our lives on one aid.
As for the US shutting it down, this is not likely to happen without notice, as there are thousands of aircraft in American airspace using GPS, nearly all as their primary aid, and the US wouldn't forget that.
As for the requirement to still have an ADF and DME fitted in UK airspace if one wishes to fly airways - why? GPS can deal with both far easier. OK, if one is going to make use of an NDB as an approach aid, that is fair enough, but there ain't so many of these around now. Could someone please tell the CAA?
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From AOPA web site:
New GPS satellite ensures future of system
When a new GPS satellite was launched on Sunday, some AOPA members wondered what it means for general aviation. The answer: GPS navigation will be around for a long time to come.
The new satellite replaces an aging bird that's nearing the end of its useful life, ensuring that the GPS signal will continue to be available even as some older satellites are taken off line.
"The latest launch represents a firm commitment to satellite navigation and demonstrates that there will be plenty of assets in space to ensure that the GPS signal is always available," said Randy Kenagy, AOPA senior director of advanced technology. "That's especially important for general aviation as more GPS-based wide area augmentation system (WAAS) approaches are created." WAAS approaches allow for ILS-like minima without the expensive ground-based equipment.
There are already several "hot spare" satellites on orbit should a GPS signal fail, and GPS availability is not a concern at this time.
The Air Force expects to launch an average of three new GPS satellites each year to replace older equipment.
September 29, 2005
When a new GPS satellite was launched on Sunday, some AOPA members wondered what it means for general aviation. The answer: GPS navigation will be around for a long time to come.
The new satellite replaces an aging bird that's nearing the end of its useful life, ensuring that the GPS signal will continue to be available even as some older satellites are taken off line.
"The latest launch represents a firm commitment to satellite navigation and demonstrates that there will be plenty of assets in space to ensure that the GPS signal is always available," said Randy Kenagy, AOPA senior director of advanced technology. "That's especially important for general aviation as more GPS-based wide area augmentation system (WAAS) approaches are created." WAAS approaches allow for ILS-like minima without the expensive ground-based equipment.
There are already several "hot spare" satellites on orbit should a GPS signal fail, and GPS availability is not a concern at this time.
The Air Force expects to launch an average of three new GPS satellites each year to replace older equipment.
September 29, 2005
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Lets remember 11Sept01, when all aircraft were ordered to land inbound to the USA, yet then, or in the days that followed, the GPS signal was not degraded or switched off.
So much for the switch off nonsense.
Now, I have been using GPS as a prime navigation aid for oceanic/long range flights for a rather long time, and in my private airplane as well, for just as long, yet I can count on exactly three times when the GPS signal faded or was not available...and never during an approach to GPS minimums.
Most of the sour grapes about the US GPS system can be traced to the 'not invented here' syndrome.
Not surprised at this at all.
That the USA thought the idea up and implemented same must be very upsetting to some...on the outside.
So much for the switch off nonsense.
Now, I have been using GPS as a prime navigation aid for oceanic/long range flights for a rather long time, and in my private airplane as well, for just as long, yet I can count on exactly three times when the GPS signal faded or was not available...and never during an approach to GPS minimums.
Most of the sour grapes about the US GPS system can be traced to the 'not invented here' syndrome.
Not surprised at this at all.
That the USA thought the idea up and implemented same must be very upsetting to some...on the outside.
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The amount of US waeponry requiring suitable GPS reception means the Americans are not going to let the system fall out of the sky. Worst case is the degradation signal is switched back on requiring crypto for precision approaches. It'll still get you over the atlantic though. Your Garmin is safe.
CBA
CBA
As for the US shutting it down, this is not likely to happen without notice, as there are thousands of aircraft in American airspace using GPS, nearly all as their primary aid, and the US wouldn't forget that.
Most of us who know its capabilities, and limitations, accept that GPS works in practice. It would appear that this is not good enough for some, and they are trying to get GPS to not work in theory......
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Blacksheep,
"Navigating with a secondary system is good practice and has been for centuries. There's not much effort involved in running a raw data cross check against an old fashioned paper map at regular intervals. How else can you be absolutely certain that your FMS is telling the truth?"
Exactly what we routinely do, that's how I knew it was accurate without GPS inputs. It's even easier when you have a moving map fed from the FMS, all that is required is to make a cross check that the displayed aircraft position ties in with a raw position from VOR/DME or NDBs.
The FMS even tells us when to change beacons on our Nav 1 box and which one it would prefer, although we do pre-empt it on most occasions because our routine checks keep us ahead of the game in that respect. We can go into various FMS info pages which tell us which satellites and ground based beacons it is using. It is usually working / computing from at at least half a dozen or so DMEs.
On this occasion, we could tell when the jamming ceased, because the aircraft symbol on the moving map twitched slightly, which probably related to about a hundred metres.
Obviously the concern is someone who might be placing too much reliance on GPS. If the whole system suffers jamming it immediately ceases to work at all.
"Navigating with a secondary system is good practice and has been for centuries. There's not much effort involved in running a raw data cross check against an old fashioned paper map at regular intervals. How else can you be absolutely certain that your FMS is telling the truth?"
Exactly what we routinely do, that's how I knew it was accurate without GPS inputs. It's even easier when you have a moving map fed from the FMS, all that is required is to make a cross check that the displayed aircraft position ties in with a raw position from VOR/DME or NDBs.
The FMS even tells us when to change beacons on our Nav 1 box and which one it would prefer, although we do pre-empt it on most occasions because our routine checks keep us ahead of the game in that respect. We can go into various FMS info pages which tell us which satellites and ground based beacons it is using. It is usually working / computing from at at least half a dozen or so DMEs.
On this occasion, we could tell when the jamming ceased, because the aircraft symbol on the moving map twitched slightly, which probably related to about a hundred metres.
Obviously the concern is someone who might be placing too much reliance on GPS. If the whole system suffers jamming it immediately ceases to work at all.
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I know that's what you good navigators do ShyTorque its what the not so good navigators do that worries me. There's ample evidence in the preceding posts that there are quite a few poor navigators flying around the skies, some of them 'Professional Pilots' too!
As a long time and highly qualified avionics specialist I've yet to encounter any foolproof 100% reliable navigation system. No matter how good and reliable the GPS is, the airborne equipment carried in today's aircraft is the same old junk that we've always had in aircraft. If avionics systems were indeed perfectly reliable, I wouldn't have a job.
As a member of the Royal Institute of Navigation and avid reader of the Institute's Academic Journal I'm also well aware of the considerable shortcomings of GPS. It isn't anywhere near as accurate or reliable as so many people seem to think - which is why the Institute recommends caution when relying on it for primary navigation.
As a long time and highly qualified avionics specialist I've yet to encounter any foolproof 100% reliable navigation system. No matter how good and reliable the GPS is, the airborne equipment carried in today's aircraft is the same old junk that we've always had in aircraft. If avionics systems were indeed perfectly reliable, I wouldn't have a job.
As a member of the Royal Institute of Navigation and avid reader of the Institute's Academic Journal I'm also well aware of the considerable shortcomings of GPS. It isn't anywhere near as accurate or reliable as so many people seem to think - which is why the Institute recommends caution when relying on it for primary navigation.
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Digital Cellular phone systems rely on GPS
I suspect it's not widely known, but digital cellular systems rely on GPS to provide "master clocking" and time synchronization at each base station. Just another reason to make sure it keeps working. I don't imagine that European cellular operators will be rushing to switch their equipment from using NavStar to Gallileo just because of its European credentials.
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EGPWS and SCATANA downing of GPS
Anybody thought about the legality implications for the mass of EGPWS users who might have a CFIT if the GPS was suddenly switched off or degraded significantly?
Let's say that at any one point in time around 7500 EGPWS using airplanes are flying around and someone pulls the GPS plug, perhaps as a SCATANA measure.
a. What will the pilot see? Just a RAIM alert?
b. Will he realize that his EGPWS is defunct? What mode will it default to?
c. Having relied for years upon EGPWS to keep him out of rock-filled clouds, is he that much more of a CFIT risk?
d. Who sues who if there's a sudden batch of deadly CFITS during a GPS outage?
e. What about if a CFIT's claimed to have been due to an intentional Defence-related degrade of the system's accuracy?
SCATANA = security Control of Air Traffic and Navigation Aids
Let's say that at any one point in time around 7500 EGPWS using airplanes are flying around and someone pulls the GPS plug, perhaps as a SCATANA measure.
a. What will the pilot see? Just a RAIM alert?
b. Will he realize that his EGPWS is defunct? What mode will it default to?
c. Having relied for years upon EGPWS to keep him out of rock-filled clouds, is he that much more of a CFIT risk?
d. Who sues who if there's a sudden batch of deadly CFITS during a GPS outage?
e. What about if a CFIT's claimed to have been due to an intentional Defence-related degrade of the system's accuracy?
SCATANA = security Control of Air Traffic and Navigation Aids
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shock...horror
<<EGPWS and SCATANA downing of GPS
Anybody thought about the legality implications for the mass of EGPWS users who might have a CFIT if the GPS was suddenly switched off or degraded significantly?
Let's say that at any one point in time around 7500 EGPWS using airplanes are flying around and someone pulls the GPS plug, perhaps as a SCATANA measure.>>
Ok, lets presume all this happened, Belgique, and all the EGPWS units in aircraft worldwide failed all of a sudden.
Hmmm, well, if you have to use EGPWS to avoid the rocky bits, then I guess you would be better off firmly on the ground.
Strange, ain't it.
Thousands and thousands of aeroplanes managed to avoid the lumpy parts simply by knowing where they are, flown by professional crews for many many, many years.
Gee, what a surprise...
Anybody thought about the legality implications for the mass of EGPWS users who might have a CFIT if the GPS was suddenly switched off or degraded significantly?
Let's say that at any one point in time around 7500 EGPWS using airplanes are flying around and someone pulls the GPS plug, perhaps as a SCATANA measure.>>
Ok, lets presume all this happened, Belgique, and all the EGPWS units in aircraft worldwide failed all of a sudden.
Hmmm, well, if you have to use EGPWS to avoid the rocky bits, then I guess you would be better off firmly on the ground.
Strange, ain't it.
Thousands and thousands of aeroplanes managed to avoid the lumpy parts simply by knowing where they are, flown by professional crews for many many, many years.
Gee, what a surprise...
411
What is the trend of aviation safety from the 1960's till now? Safer or more dangerous?
I've seen a lot of posters talk about intentional shutdown and how it likely wouldn't happen. What about unintentional shutdown? MIJI anyone. Isn't an unintentional signal loss enough to make sure you know where you are independant of GPS?
What is the trend of aviation safety from the 1960's till now? Safer or more dangerous?
I've seen a lot of posters talk about intentional shutdown and how it likely wouldn't happen. What about unintentional shutdown? MIJI anyone. Isn't an unintentional signal loss enough to make sure you know where you are independant of GPS?
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You don't need GPS to use EGPWS. I've flown plenty of aircraft that have EGPWS fitted but not GPS. You just need to make sure you do nav accuracy checks to ensure the FMS/IRS position is within tolerance compared to the raw data position.