I've never heard that or seen any evidence of it. We've met Canadians
just recently that cruise to Cuba quite frequently and they reported
no such issues. It would be technically difficult to jam GPS signals
over any distance other than by satellite or high altitude airplane.


I understood that "selective availability mk2" (or whatever it's known as) is
the capability to selectively deny access to GPS signals over limited
geographical areas, maybe this has some bearing ?

Boo

On Sat, 17 Jul 2010 11:22:42 +0100, Boo
wrote:

I understood that "selective availability mk2" (or whatever it's known as) is
the capability to selectively deny access to GPS signals over limited
geographical areas, maybe this has some bearing ?

It would be limited mostly to "line of sight" distances, and Cuba is
not known for being a technical power house with unlimited financial
resources.

Wayne.B wrote:

On Sat, 17 Jul 2010 11:22:42 +0100, Boo
wrote:

I understood that "selective availability mk2" (or whatever it's known as) is
the capability to selectively deny access to GPS signals over limited
geographical areas, maybe this has some bearing ?

It would be limited mostly to "line of sight" distances, and Cuba is
not known for being a technical power house with unlimited financial
resources.

You and the previous poster are giving the appearance of not knowing
what selective availability (SA) is. SA is a feature of GPS that permits
the civilian positioning feature of GPS to be subject to a psuedo random
position error. This error affects all GPS units within a particular
area and is only "line of sight" in that it affects all units within
line of sight of particular satellites, so the area can be huge or
indeed global as it was until 2000 when the feature was turned off. Your
comment makes it appear that you are confused between jamming and SA.

At present GPS is denied in particular areas using other means which are
less susceptible to correction. SA could be defeated by the use of dGPS
and the US have stated it will never be turned back on again.

You seem to have been attempting to claim that GPS cannot be jammed or
denied, in this you are wrong. The methods used are not however public
knowledge although from time to time NOTAMS and similar publications
will indicate in which areas GPS is being denied for trials.

On Sat, 17 Jul 2010 14:35:36 +0100, (Steve Firth)
wrote:

You seem to have been attempting to claim that GPS cannot be jammed

Incorrect. I am claiming that it is unlikely that GPS is being jammed
by the Cuban government.

Wayne.B wrote:

On Sat, 17 Jul 2010 14:35:36 +0100, (Steve Firth)
wrote:

You seem to have been attempting to claim that GPS cannot be jammed

Incorrect. I am claiming that it is unlikely that GPS is being jammed
by the Cuban government.

Well no, and you had to trim a lot from my post to cover up the mistakes
you made. FWIW, jamming is low tech and the Cuban government is probably
able to do it as well as the British government. OTOH if GPS is being
jammed near Cuba, I'd point the finger towards another government with a
rabid hatred of Cuba.

On Sat, 17 Jul 2010 20:52:41 +0100, (Steve Firth)
wrote:

Incorrect. I am claiming that it is unlikely that GPS is being jammed
by the Cuban government.

Well no, and you had to trim a lot from my post to cover up the mistakes
you made. FWIW, jamming is low tech and the Cuban government is probably
able to do it as well as the British government. OTOH if GPS is being
jammed near Cuba, I'd point the finger towards another government with a
rabid hatred of Cuba.

Have you ever looked at the age and detail level of the commonly
available Cuban charts? If so, you'd know that the problem is not
with GPS. I was cruising within 40 miles of the Cuban coast just a
month ago and our GPS was spot on with up to date electronic CMAP
charts of the area. Cruise ships and commercial shipping transit
within sight of the Cuban coast all of the time and they are having no
issues. What *is* happening, is that some, but by no means all,
cruisers are getting into trouble because of bad charts and/or
inattention. When that happens it is much less embarassing to blame
the whole incident on mysterious forces and conspiracy theories.

PS, no one in the US really hates Cuba except for a small number of
reactionaries who escaped after the Castro takeover.

In article ,
Wayne.B wrote:

On Sat, 17 Jul 2010 14:35:36 +0100, (Steve Firth)
wrote:

You seem to have been attempting to claim that GPS cannot be jammed

Incorrect. I am claiming that it is unlikely that GPS is being jammed
by the Cuban government.

Not to dis Wayne, but MANY Governments that are NOT Allies with the USA,
have purchased GPS Jamming Technology, from the Russians, for the simple
Paranoid Reason, that they can turn it ON, and it will keep some of our
Lower Tech GPS Guided Munitions from hitting their intended Targets,
should we feel the need to go to War with them.... Most of the more
Modern Guided Munitions now use other Primary Guidance Systems, and GPS
is only a Backup Slave System, that can be set to be compared with the
Primary System.
These same Governments, test these Systems regularly... Our own
Government DOES protect MANY of our most important Federal AREAS, using
similar Technologies, for the same reasons. GPS is great, but it is NOT
the One Size Fits ALL Munition Aiming System....

--
Bruce in alaska
add path after fast to reply

Bruce in alaska wrote:

Most of the more Modern Guided Munitions now use other Primary Guidance
Systems

Great Random CaPitalisation tHere.

FWIW, a great many Old Guided Munitions use other Primary gUiDancE
sySteMs.

On Sun, 18 Jul 2010 12:19:23 -0800, Bruce in alaska
wrote:

Not to dis Wayne, but MANY Governments that are NOT Allies with the USA,
have purchased GPS Jamming Technology, from the Russians,

It was never my point that GPS could not be jammed. My point was,
and is, that such jamming would by necessity be relatively short range
because of the microwave frequencies involved. The only exception
would be some sort of systemic jamming that originated within the
satellites themselves. It's my understanding that jamming of that
sort would affect all users.

"Steve Firth" wrote in message
.. .
Wayne.B wrote:

On Sat, 17 Jul 2010 11:22:42 +0100, Boo
wrote:

I understood that "selective availability mk2" (or whatever it's known
as) is
the capability to selectively deny access to GPS signals over limited
geographical areas, maybe this has some bearing ?

It would be limited mostly to "line of sight" distances, and Cuba is
not known for being a technical power house with unlimited financial
resources.

You and the previous poster are giving the appearance of not knowing
what selective availability (SA) is. SA is a feature of GPS that permits
the civilian positioning feature of GPS to be subject to a psuedo random
position error. This error affects all GPS units within a particular
area and is only "line of sight" in that it affects all units within
line of sight of particular satellites, so the area can be huge or
indeed global as it was until 2000 when the feature was turned off. Your
comment makes it appear that you are confused between jamming and SA.

At present GPS is denied in particular areas using other means which are
less susceptible to correction. SA could be defeated by the use of dGPS
and the US have stated it will never be turned back on again.

You seem to have been attempting to claim that GPS cannot be jammed or
denied, in this you are wrong. The methods used are not however public
knowledge although from time to time NOTAMS and similar publications
will indicate in which areas GPS is being denied for trials.


Exactly right Steve,
Washington DC and Fort Hood in upstate NY are just
two places I have personal knowlege of where GPS is
munged for security purposes.
Regards,
JR