Could a handheld GPS interfere with the INS system?

[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.