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.

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.

True, but America is ?

Boo

Wayne.B wrote:

Have you ever looked at the age and detail level of the commonly
available Cuban charts?

No, I looked at the bilge you were talking about GPS and pointed out
that it was bilge. And for some reason (lack of balls, inability to
admit fault?) you keep running away from your failure.

No one mentioned "conspiracy" or "mysterious forces" before you started
wibbling about them.

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

Right, so your government hasn't had sanctions in place against Cuba
since the 1950s? Oh look, porcine aviation.

Perhaps you could learn to read BTW. I pointed out that your government
has a rabid hatred of Cuba. You then tried to turn that into a
generalisation about Americans with your "no one in the US" bull.

"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

Steve Firth wrote:
Wayne.B wrote:

Have you ever looked at the age and detail level of the commonly
available Cuban charts?

No,

So you know nothing about Cuban charts.
And you know nothing about GPS navigation in Cuban waters.
Does that sum it up?

Jim