[time-nuts] How hard is it to detect a GPS Jammer?

Chris Albertson albertson.chris at gmail.com
Tue Oct 8 20:33:56 UTC 2013


It does no good to prohibit clients from using GPS on land because unless
you keep them blindfolded the entire time they will see and photograph
their surroundings.  People with some training can find location to within
about 25 feet with no GPS even in a flat dessert.   I've hiked out to find
a tent stake that was placed there by an instructor in open dessert.  We
photo the stake then hike back.  THose who don't know the tricks can
certainly find a location to within a 1/2 mile.

The only place this makes sense is on the ocean when you are not within
sight of land.  There ARE some fishing boat captains who ask clients not to
use the GPS.   But people cheat and turn on the GPS and leave it packed in
a bag and let it run until the battery dies.  This way they are never seen
using it.    This is rare because usually fish move and yesterday's good
spot is of no use.  Many of the boats hire a spotter who works from an
airplane.  But then "everyone" uses one of only two spotters who fly in the
area.


On Mon, Oct 7, 2013 at 10:37 PM, David I. Emery <die at dieconsulting.com>wrote:

> On Mon, Oct 07, 2013 at 11:30:57PM -0500, Bill Hawkins wrote:
> > In general, we expect a jammer to be involved in criminal activity.
> >
> > What about a wilderness guide whose reputation is built on finding
> > the best spots to view Nature's wonders. Should he or she be happy
> > to let people in the guided group save the coordinates of those
> > spots in order to compete with the guide or avoid guide's services
> > in the future?
> >
> > Or would that be a justifiable use of jamming?
>
>         No.
>
>         Jamming can potentially impact a much wider area and safety of
> life critical uses of GPS, and  very few wilderness guides are expert
> enough to understand, control and mitigate this risk.   And even if one
> particular one was, how is this to be reliably ensured ? Should  he or
> she be licensed and certified and regulated as to how and when he might
> jam safely - we don't current issue GPS denial licenses (except maybe to
> LightSquared) ?
>
>         And even with someone suitably trained and licensed and
> certified there is a balance between the slight risk that his jamming
> harm something important or critical that society relies upon and his
> own personal interest in denying GPS to his customers that I am not sure
> we as a society have quite figured out.   Should private businesses be
> allowed to deny GPS (or for that matter cellphone access) to folks
> nearby or their customers - is this a legitimate interference with a
> public resource ?
>
>         Obviously if the answer is yes, businesses should be allowed to
> jam cellphones or GPS - then what are the limits - eventually all those
> private jammers will make such services MUCH less useful - as they will
> be unpredictably unreliable at apparently random times and places which
> makes it very hard to trust them for anything important.   We will in
> other words have allowed the private interests of certain folks to
> destroy a commons, something we are getting increasingly good at BTW.
>
>         I suppose it is SOMEWHAT justified for a guide to search his
> customers for GPSes, or have a strict policy of dropping them off at the
> nearest road if they are found to be using one, or even to use a GPS
> detector to ID GPSes in use... but an active attack seems wrong given
> the risks involved.
>
>         And anything more nuanced in a policy on such invites various
> low life scumbags to push the limits and use blatantly excessive power,
> dangerous antenna locations, and generally horrid engineering that puts
> important uses and users of the technology at serious risk for very
> selfish personal reasons - perhaps in some cases just buying some cheapo
> jammer instead of a proper licensed and limited one managed and
> installed by someone who knows what he is doing.
>
>         Finally of course, who is to say that I cannot use my cellphone
> for important messages - perhaps life critical (my wife is a doctor and
> does this from time to time when she is on call)... or my GPS to locate
> a store somewhere... perhaps if the jamming ONLY worked in a completely
> private space owned or controlled by the jammer and not at all outside
> of it would this begin to be marginally acceptable but it certainly
> isn't in public spaces.  And I believe there should be mandatory readily
> visible notices saying that jamming is use... allowing someone who
> truly needs access to know what is happening.
>
>         As for the wilderness case specifically there are any number of
> strategies to defeat short range jamming of that sort - just announce
> you have to "go" as the group leaves the scenic knoll and go back and
> take a bearing (maybe automatically from a concealed GPS you already
> have in you backpack) while peeing on the special rock...   Inverse
> square law applies here of course... hard to radiate enough power to
> deny over a long enough distance without being completely unsafe for
> other users.
>
> --
>   Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston,
> Mass 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole -
> in
> celebration of what could have been, but wasn't and is not to be now
> either."
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California



More information about the Time-nuts_lists.febo.com mailing list