Could a handheld GPS interfere with the INS system?

[411A]

Good God, some here are still complaining about GPS being 'switched off' by the US DoD.
Get over it, ain't gonna happen, full stop.

Can it be used stand alone on the north Atlantic, as a primary means of navigation?
You bet...and I have done so many times.
Dual (or triple) Honeywell HT9100 units have been thus used for over ten years.
'Tis a fact.
Can an INS/IRS be updated with GPS?
You bet, as others have correctly indicated.

And as for BEagle...of course it was a Collins unit, the best there is, bar none.
Except...perhaps for Hamilton Sundstrand, the heart of the L1011 FMS.
Ahhh....Lockheed!

[Life's a Beech]

An INS update includes an alignment to true north. That's why it must be done stationary and takes several minutes - it is detecting the rotation of the Earth. That can't be done with GPS!

OK, so technically there have been tests with GPS in each end of an aircraft to find heading, but it is nowhere near as accurate as fine alignment on an INS or IRS.

[IO540]

The handsets are always making search transmissions and at full power. When they can't get a response they ramp up the power and try again. At high power outputs the transmission power is sufficient to break through on my tape player.

Is the above for a GSM network? Surely not. AFAIK GSM phones remain silent until they pick up a signal from a tower. Then and only then they run the protocol with that, at a power which is adjusted according to how strong the incoming is (stronger means less power is required from the phone).

I still don't believe there is a significant chance of a mobile phone interfering with anything.

Which is a different thing from banning them as a precaution....

[Self Loading Freight]

Shame there isn't a GPS Receiver on the market which could use the US, Russian and soon to be Gallieo systems for error checking and failure warning.

There will be, just as soon as GLONASS and Galileo are reliable - or, indeed, exist. GLONASS is still recovering from being left to rot in orbit, and has very poor coverage over most of the world - less than 25 percent availability in lots of places. There are also questions over whether it'll adopt GPS compatible signalling. It's not yet stable or reliable enough to support.

Galileo is still a long way from being operational at all, but I know that GPS receiver makers are intending to include Galileo capabilities. It won't be difficult or expensive when the time comes and there's no real reason not to, but the designers aren't sure how useful it'll actually be.

R

[NSEU]

"I have to call you on that one. There is no IRS/IRU/ADIRU that updates from any external source...in any civil aircraft, be it Honeywell, Litton, etc. The FMC (FMS) will up date from GPS/DME/LOC/VOR."

Many years ago (pre-FMC), we had direct DME inputs to our 747 Classic INU's. Note that INU's are different from IRU's in that INU's have full navigation capabilities. IRU's require FMC's.

However, I guess you could argue the definition of "updating". During DME updating on our Classic 747's, DME-only position is used for navigation (not the inertial position), although the two values are compared for reasonableness inside the INU. You could say that the DME is not really modifying the basic inertial position, but the INU itself is outputting more accurate (DME) data.

This system was very labour intensive and involved manually inserting DME station info via the CDU.

Rgds.
NSEU

[Spooky 2]

Was that a Collins AINS70 by chance?

[Dan Winterland]

Blimy BEagle, I remeber that diagram. Was the blue box on the left the oven? The most essential piece of equipment on an RAF tanker!

And as for GPS set being as common as mobile phones, Mrs W actually has a GPS built into her mobile phone!

No GPS could ever cope with the magic roundabout! Reminds me of the true tale of the American exchange officer who on his first excursions onto the British roads happened across the said roundabout. After going round three times, he decided he couldn't get out of it, parked his car in the middle and waited for the police to arrive!

[BEagle]

No, not the oven! It was the JTIDS terminal (used ac posn and air data).

You're right about the oven though - most essential!

I can well believe the confusion the magic roundabout would cause to a US Exchnage Officer - it'd be hard enough for him to remember to drive on the left, let alone cope with the 5 linked mini roundabouts!

[el_visigodo]

Russians launch three more navigation satellites

GLONASS is still recovering from being left to rot in orbit, and has very poor coverage over most of the world - less than 25 percent availability in lots of places.

"The full constellation of 24 satellites, scheduled for completion in the next two years, will allow the system to reach users worldwide."

http://www.spaceflightnow.com/news/n0712/25glonass/

[ankh]

One source, no problem; many sources, you get spikes.

Following the pointer from the active 777 topic, for those thinking about electronic interference. There may be no interference at all from one source in one mode, or in any of its modes.

Combining two variable sources gives an inordinate number of possible combinations.

Combining all the sources passengers may have active at any moment gives in inestimable number of combinations.

What do we know about combining a great many waveforms? On a two-dimensional surface, quite a bit, although this work has become a worry only very recently because it explains a problem long considered a myth, until photographs and satellite instruments show it happens:

http://www.ams.org/mathmedia/archive/01-2003-media.html

" BBC Two, on November 14, 2002, aired a program on this phenomenon and its recent mathematical analysis. Freak waves, also "rogue waves," "monster waves," are extraordinarily tall and steep waves that appear sporadically and wreck havoc with shipping. One is suspected to have washed away the German cargo München which went down with all hands in the midst of a routine voyage in 1978. More recently, the cruise ship Caledonian Star was struck by a 30m wave on March 2, 2001. The standard analysis of ocean waves predicts a Gaussian-like distribution of heights; extreme heights, although possible, should be very rare - a 30m wave is expected once in ten thousand years, according to the BBC. But these waves occur much more frequently than predicted. The program focused on new methods of analysis, and on the work of the mathematician A. R. Osborne (Fisica Generale, Torino). Osborne has applied the inverse scattering transform, which he describes as "nonlinear Fourier analysis," to the time series analysis of wave data. He conducted simulations using the nonlinear Schrödinger equation and found near agreement with the standard analysis, except that "every once in a while a large rogue wave rises up out of the random background noise." His paper ... gives an example of such a simulation:

http://www.ams.org/mathmedia/images/wavetrain.gif

See the spike? Put the spike into your onboard electronics. There will be a spike strong enough to overcome the specified sensitivity protection, somewhere in 3-dimensional space inside the aircraft, at some point. Most of them won't coincide with anything that will interpred the spike as a signal. Some of them will. Some of the software won't reject that as an incorrect signal.

On a two-dimensional surface, the ocean, such a spike (rogue wave) can break a long oil tanker in half. The tanker design assumes there are no such waves -- they weren't observed when the designs were established and nobody's tried to reinvent the oil tanker to build one capable of surviving these events. They lose a few, cost of doing business -- until now nobody could do the statistics, they didn't believe rogue waves happened!

The Japanese had a term for this long ago, in a very dense population with a lot of electronics and electrical gear and little in the way of shielding -- "electronic smog."

The first deaths from unexpected activation of electronic equipment due to this were reported over 20 years ago.

http://intranet.cs.man.ac.uk/Study_s...P10070/KR_real

-----excerpt----
A series of mysterious deaths in which industrial robots suddenly attacked and
killed humans is being investigated in Japan, news reports said yesterday. Ten
people have been killed by robots in the last eight years. In four cases,
operating errors were blamed. In the other accidents, the robots suddenly
started working for unexplained reasons, according to reports. Witnesses
listed a number of cases in which the robot suddenly stretched out its
mechanical arms, killing its victim. Experts plan to test a theory that
electromagnetic waves in factories have been responsible for setting off the
sensitive computer mechanisms in the robots.

[We had previously documented the 1981 Kawasaki case, and noted reports of at
least four more (and possibly as many as 19) robot-related deaths.]

http://catless.ncl.ac.uk/Risks/4.91.html#subj1.1
CHIPS ARE DOWN OVER ELECTRONIC POLLUTION
The Guardian, 26 May 1987
"Lindsay F. Marshall" <lindsay%[email protected]>

Japan is engulfed in an "electronic smog" which has caused deaths and injuries,
and jammed an airport radar system, according to recent findings.

Electronic smog occurs when electromagnetic waves from equipment like personal
computers and electronic game machines "escape" and trigger other machines. An
electromagnetic wave can also be caused by a mere spark. An electric spark
from a crane operating in a valve plant set off a lathe-operating robot in
1982 killing an assembly-line worker.

http://catless.ncl.ac.uk/Risks/2.42.html#subj1.1
Date: Mon 14 Apr 86 09:19:46-PST
From: Ron Cain <[email protected]>
-----end excerpt------

Remember -- the more signals you have, the more they will overlap, and the energy in the waves is additive so you _will_ get 'rogue' spikes of very strong signal that come from no identifiable individual source -- they come from the interaction of many signals that is momentary and not reproducible.

And we're at a sunspot minimum right now, so you can't blame it on sunspots. In a few years, though, those will be adding to the effect.

[Self Loading Freight]

While it's possible for lots of different EM radiating sources to coincide and produce unusual peaks of energy, that would be extremely difficult to categorise in any useful way other than by observation. My head hurts with the idea of creating even a crude mathematical model of an aircraft full of bored punters playing with their gadgets. I've seen how researchers model office conditions for WLAN design, and even when you're limiting the radios to one design doing one job on one band, it's devilishly difficult to get useful answers - at one point they started to put sacks of saline solution in the chairs to model absorption by bodies - and the speed at which technology changes means you can't spend years trying all these ideas.

But that doesn't mean it's not possible to get useful results. Ideally, the aviation and ICT industries would work together to create and run a testing regime that models real life as closely as possible.

[BobT]

IO540 nails it.

While the theoretical discussion is interesting, we've by now a good amount of practical experience that strongly indicates that EMI from consumer devices isn't much of an issue if any.

Think about the numbers of emitters (mobiles, laptops, Playstations, digicams, DVD players, Ipods, etc. etc.) that have been used in all phases of flight. No aircraft down under mysterious circumstances...

[ankh]

> While it's possible for lots of different EM radiating sources to coincide
> and produce unusual peaks of energy, that would be extremely difficult
> to categorise in any useful way other than by observation.

It's more than 'possible' -- it's physics. It happens.

Look up the very new field of research on 'rogue waves'

These are being described now in light and other electromagnetic terms as well as on the surface of the ocean. Once people realized these things really happened and can explain the odd number of losses of the largest ships, and observed them, the research took off fast.

Example, recent work only; some of these likely relate to what's happening in an environment like the inside of an aircraft:

http://scholar.google.com/scholar?nu...07&btnG=Search

First hit in that search (abstract only, you'll have to visit a library or Google for the authors' bibliography pages or other sources to see more):

http://www.nature.com/nature/journal...l/450953a.html

Nature 450, 953-954 (13 December 2007)
doi:10.1038/450953a; Published online 12 December 2007

Photonics: Rogue waves surface in light

Dong-Il Yeom & Benjamin J. Eggleton

Abstract

How do the freak waves that haunt seafarers' nightmares arise? We don't know, is the short answer — but the discovery of a similar phenomenon in optical waves might assist in getting to the bottom of the mystery.

Oceanic rogue waves — monstrous sea waves that form spontaneously and can reach up to 30 metres in height— have been held responsible for marine misfortunes ranging from the sudden sinking of seagoing ships to damage to oil platforms. They are not just the stuff of maritime folklore ...

----- end abstract ---
From the related links provided, this:
Nature 450, 1054-1057 (13 December 2007) | doi:10.1038/nature06402; Received 22 February 2007; Accepted 11 October 2007
Optical rogue waves

D. R. Solli1, C. Ropers1,2, P. Koonath1 & B. Jalali1

1. Department of Electrical Engineering, University of California, Los Angeles 90095, USA
2. Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, D-12489 Berlin, Germany

Correspondence to: D. R. Solli1 Correspondence and requests for materials should be addressed to D.R.S. (Email: [email protected]).



Recent observations show that the probability of encountering an extremely large rogue wave in the open ocean is much larger than expected from ordinary wave-amplitude statistics1, 2, 3. Although considerable effort has been directed towards understanding the physics behind these mysterious and potentially destructive events, the complete picture remains uncertain. Furthermore, rogue waves have not yet been observed in other physical systems. Here, we introduce the concept of optical rogue waves, a counterpart of the infamous rare water waves. Using a new real-time detection technique, we study a system that exposes extremely steep, large waves as rare outcomes from an almost identically prepared initial population of waves. Specifically, we report the observation of rogue waves in an optical system, based on a microstructured optical fibre, near the threshold of soliton-fission supercontinuum generation4, 5—a noise-sensitive5, 6, 7 nonlinear process in which extremely broadband radiation is generated from a narrowband input8. We model the generation of these rogue waves using the generalized nonlinear Schrödinger equation9 and demonstrate that they arise infrequently from initially smooth pulses owing to power transfer seeded by a small noise perturbation.

------end of abstract ----

Much more information available. Serious, very new science being done.

One last thought -- put the signal generators inside a Faraday cage -- airliner, train, or bus -- and you get intensities above those outdoors.

That's being studied as well, for example:

Electric-Field Distribution Estimation in a Train Carriage due to ...

The electromagnetic field (EMF) distributions created inside a train ... A simplified histogram estimation method for electric field strength is newly ...
http://ietcom.oxfordjournals.org/cgi...t/E88-B/8/3281

How much more or less sensitive is aircraft electronics at any individual particularly exposed spot in the cabin than, say, a cardiac pacemaker?

----abstract---
The electromagnetic field (EMF) distributions created inside a train carriage by the cellular radios of the passengers are analyzed and the impact their electromagnetic interference (EMI) on the implantable cardiac pacemakers is evaluated based upon the analysis results. Both computer simulations and experiments using 800 MHz and 2 GHz transmitters in an actual train carriage confirm that excessively high EMF, high enough to affect the normal functions of the pacemaker, does not occur inside the carriage provided the safe distance of 22 cm specified for pacemaker users is kept. A simplified histogram estimation method for electric field strength is newly developed to deal with the complicated EMF distributions. It allows the EMI risk to pacemakers by cellular radio transmission to be quantitatively evaluated. Methodologies are described first. Typical results of FDTD analysis and actual measurement data are then shown. Finally, considerations and conclusions are made.


---end abstract----

So -- there's more science news every day. Opinions don't change nearly as fast as what's actually known. Always worth looking up what's known, today, compared to yesterday.

[rossmi]

Following on from this discussion ... is it known to what altitude the 'electronic fog' might affect an aircraft's equipment? I'm researching the vulnerabilities of GPS for a security project and am trying to get a handle on the risk of interference.

There was a post in a thread in 2002 ('GPS jamming over most of UK') which mentioned a faulty GPS receiver jamming all other receivers nearby. A brief web search suggests that any Government road toll scheme would motivate many car drivers to use GPS jammers - to avoid being tracked. Would this 'electronic fog' in the L-band affect all aircraft, perhaps, or only at aerodromes close to motorways? Can anyone offer some suggestions?

Then there is the possibility of GBAS being tripped by 'electronic fog' near its GPS receivers ...

thanks

[Geezers of Nazareth]

The use of a GPS device on an aircraft in-flight (or on the ground, if it comes to that) interests me. I have a small GPS which I have used on a flight back from Paris a few years ago, and I still have a copy of the 'track' flown from gate to gate. It only really works if you place it by the window, so that it can 'see' the satellites.

In March last year I was in the USA and did a little flight in Arizona. I asked the pilot if I could use my GPS during the flight, and he was quite happy with it. In fact, he suggested placing it on top of the instrument panel so that it would get a better signal. During the flight I asked the pilot about possible interference, and we moved the GPS around several times, trying to get a reading on any of the instruments. Nothing, nada, zip!

On long distance flights I get bored, so I like to look out of the window and look at various features on the ground below. Later, if I'm able, I try to find these things on Google Earth, to see what else I can find out about those places. Having a GPS makes it so much easier. I can record a location (or 'waypoint', or POI, in GPS terms) for later use.

I find that the moving map display on the 'in flight' entertainment system is completely useless, and nowhere near accurate enough for what I want to do.
As somebody suggested above, do you seriously expect me to go and knock on the cockpit door to ask the pilot for a lat/long readout?? How about if I do this every 30 minutes over the entire flight? How long do you think they would continue to answer the knocks on the door?



There is a product on the market which I have been considering. It is called a 'Trackstick'. It is a small GPS receiver with a memory; it can be programmed to record its location every 1 minute, or every 5 minutes, or every hour, or whatever. Later, the whole set of location recordings can be downloaded for later use or analysis. There's no display on a Trackstick, so you can't instantly see where you are.
So, with a suitable Trackstick placed next to the aircraft window, set to record its position every minute, if I see anything of interest on the ground below I just need to make a note of the time and what I saw, and when I download the data from the Trackstick I can match the two to see where I was.



Going back to my original comments - my GPS device is a small grey box about the size of a box of matches. It uses Bluetooth to communicate with my mobile phone. So, I set the phone to 'flight safe' (as allowed by the airline), and use a Bluetooth connection (also as allowed by the airline) ... what am I doing wrong?

[Dream Land]

I'm no technician but I would say what you're doing affects no one, I know several pilots that do the same thing on the flight deck, happy navigating.

[ModernDinosaur]

An interesting anecdote regarding GPS. One system I used about three years ago had two GPS receivers and checked one against the other. One day, receiver 'A' reported no satellites were visible, while receiver 'B' showed a sky-full, albeit it slightly reduced signal level compared to normal. We tried changing the antenna on receiver 'A' for a known-good unit, but still couldn't see any satellites. We scratched our heads for a bit until I suggested using the antenna we'd just removed on receiver 'B' instead. That one change brought BOTH receivers back to life, with strong signals from all satellites. A lab investigation showed that the low-noise amp in the antenna which was originally on receiver 'B', the one that appeared to be working, had developed a fault and was acting as an oscillator which was blocking the other antenna, located some 20m away.

Now imagine your personal GPS has a similar fault. You're sitting in the cabin of an airliner satisfying your curiosity by looking at your moving map, oblivious of the fact that your kit is interfering with the aircraft's GPS. Not a problem in a light aircraft since generally the pilot knows full well that someone in the back seat is using a GPS and can ask them to turn it off if they have the slightest suspicion of a problem. How about the Captain flying 200+ passengers? He or she has absolutely no idea why his GPS doesn't work any more - and if in IMC, they may not even be aware that it's not working.

In general, during critical phases of flight (loosely those which occur within 10,000' of the ground for an airliner), I make darned sure that all of my personal electronic devices are turned off if they can be. I do draw the line at my wrist watch, and if I had one, I'd probably leave my pacemaker on too

It appears from the accident rate that the risk is low even for devices which are designed to transmit (e.g. the infamous cellphone), although there is a growing body of evidence that non-critical system interference does occur fairly regularly. But why take that risk? Is a text message really worth 200 lives?

[ex jump pilot]

Re in flight mags and using "electronic equipment".
I've flown with BA a few times.... Their in flight mag* (plus web site) says that receivers are fine once the seat belt light is off. I've used my GPS on many flights with subsequent enjoyment when the results have been plotted. Can't always get a signal from a window seat but mostly it's fine. N Atlantic to Denver last month wasn't too hot nor was LHR to LAX last April at times. Brazil to LHR gave a wonderful track all the way overnight (had the GPS between the blind and the window).

Considering most receivers are run from a 1.5 or 3 volt battery, I think they would be hard pressed to generate much interference. LCD screens generate noise (my air band radio will pick it up within about 18" (say 45 cms) of my lap top and personal organiser. Somehow, I don't think that would be strong enough to affect equipment in a modern aircraft.

As for mobiles. They have considerably more radiated power and I reckon it's not a good thing to leave one on. However, I suspect aircraft are more than resilient enough against them.

The "test reports" about RFI and aircraft that I have followed up seem very dated and use language that appears to be deliberately ambiguous.

Lastly, whilst it's no bad thing that all "distractions" are put away during landing and take-off, I think it's a bit "we love telling you what to do" by stating no mobiles are to be on until you are safely inside the terminal. Probably more to do with emptying the aircraft faster for a speedier turn around?

One final thought. In the 1930s, death rays against aircraft were wildly popular. Is there a resurgence?

* I think that easyJet also allow receivers to be used. Will be having a go next month though the route is pretty direct so no surprises there.