[ntp:questions] GPS Jammers in Use by Criminals - Warping Time for Fraud Suggested

unruh unruh at invalid.ca
Thu Feb 23 21:40:33 UTC 2012

On 2012-02-23, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> On 2/22/2012 5:16 PM, David Woolley wrote:
>> An article in the Metro, the free morning paper on the London commuter
>> transport network, suggests that criminals may be using GPS jamming
>> equipment to warp the time on financial systems to allow the commission
>> of fraud.
> GPS is not the only source of time!
> In the U.S. 60 cycle Alternating Current is the standard and the source
> of time.  It's not going to give you the nanoseconds but very few people 
> could even explain what a nanosecond is let alone needing nanosecond 
> resolution.

It is neither a standard nor is it a "source of time". The requirement
is that the phase of the 60Hz be the same across the country, so
electricity can be traded between generation facilities without one
source shorting out the other. That does not require frequency accuracy,
just that the frequency of all the generators be the same and the phase
difference be less than  a ms or so. 

Because the easiest way to ensure phase coherence is to demand frequency
coherence and use a standard, like UTC, as a reference, they do tend to
be close. But the requirement is phase coherence not time accuracy and
the latter will be jettisoned in favour of the former.

>> Although I can't find the source of that article, the BBC has an
>> article, presumably from the same underlying source, addressing another
>> point in that that article, that GPS jammers are increasingly being used
>> to defeat GPS based car tracking systems.
> If anyone wants to track my car's location, you're welcome.  And I hope 
> that no one dies of boredom!

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