GPS - Out in Front -- Fess Up

Author

Out in Front -- Fess Up

Sam Wormley

2007-06-18, 10:33 pm

Out in Front -- Fess Up
http://sidt.gpsworld.com/gpssidt/ar...l.jsp?id=429734

Jun 1, 2007
By: Alan Cameron
GPS World

Galileo proponents have finally acknowledged that public funding
presents the only feasible way to launch a satnav system. Now that
they have shed the PPP illusion, it behooves us all to examine other
Galileo myths, rehearsed again in a recent Financial Times article.
The press picks up these embroideries and perpetuates them; they do a
disservice to the satnav community.

Galileo will be more accurate than GPS. This highly exaggerated claim
is just plain wrong. GPS accuracy and GPS clocks continue to improve,
and added ground stations enhance orbit predictions. While the
experimental Galileo signal from its experimental satellite, as
reported here last month, indicates better accuracy than current GPS,
most experts believe GPS accuracy will exceed Galileo's by the time
the latter finally gets airborne.

A civilian-controlled Galileo will be more reliable than the military
GPS, which could be switched off at any time. GPS has been incredibly
reliable, to a large extent because its funding and military
commitment have been so stable. Can Europe's approach assure such
stability? That the United States would switch off GPS signals is
indeed a modern myth. Even were there such a technical ability --
which there isn't -- it would be politically impossible.

Galileo will give a mobile phone user directions to wherever. Ships
and aircraft will become more efficient. Emergency services could
pinpoint incoming calls. The implication that GPS furnished car
navigation and a few other handy things, but that Galileo will enable
far more, again misleads. GPS already does all these things. Galileo
will contribute by adding more interoperable signals, not special
signals or services. GPS makes ships and aircraft highly efficient;
more satellites won't help much in that arena. More signals will
primarily benefit users in obstructed places such as urban and
natural canyons.

A whole series of applications cannot be developed without two key
Galileo aspects: guarantee of service and accuracy. What guarantee
will a government-funded Galileo provide? What does that mean,
anyway? If it means integrity messages, they are available in Europe
from EGNOS and in North America from WAAS. Further, with 50 to 60 GPS
and Galileo satellites, receivers can determine integrity on their
own with receiver autonomous integrity monitoring. I have yet to hear
of anyone really wanting Galileo integrity messages to the extent of
paying for them.

I have already dismissed the accuracy claim. The "two key things"
don't add up to a difference that would make Galileo valuable on its
own merits. Its value lies in doubling interoperable signals.

Such Galileo "advantages" represent wishful thinking, not reality.
Galileo officials should stop selling myths and instead justify
Galileo for its true benefits: more satellites with interoperable
signals, and a subsidy to encourage a vigorous space industry. GPS
industry and users should be fully aware of same. Using real reasons
in a forthright manner, rather than fabricated ones appealing to
national vanity or sovereignty, will serve Galileo much better than
current-generation mythology.

See: http://sidt.gpsworld.com/gpssidt/ar...l.jsp?id=429734

Happy Trails

2007-06-19, 4:33 am

>Out in Front -- Fess Up
> http://sidt.gpsworld.com/gpssidt/ar...l.jsp?id=429734
>
> Jun 1, 2007
> By: Alan Cameron
> GPS World
>
> Galileo officials should stop selling myths and instead justify
> Galileo for its true benefits: more satellites with interoperable
> signals,

I agree with the intent and facts of this article.

However, this supposed interoperability is a further myth.

And until the operators of all systems agree on a single time source,
and manage to adhere to it, it will remain a myth.

Gary

2007-06-19, 10:33 am

"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:hnFdi.109605$n_.89404@attbi_s21...
> Out in Front -- Fess Up
> http://sidt.gpsworld.com/gpssidt/ar...l.jsp?id=429734
>
....
> A civilian-controlled Galileo will be more reliable than the military
> GPS, which could be switched off at any time. GPS has been incredibly
> reliable, to a large extent because its funding and military
> commitment have been so stable. Can Europe's approach assure such
> stability? That the United States would switch off GPS signals is
> indeed a modern myth. Even were there such a technical ability --
> which there isn't -- it would be politically impossible.
>
I don't know anything about the technical ability but to dismiss anything as
being "politically impossible" is to ignore the chutzpah of almost any U.S.
administration and especially of the current one!

SteveG

2007-06-19, 10:33 pm

>
> A civilian-controlled Galileo will be more reliable than the military
> GPS, which could be switched off at any time. GPS has been incredibly
> reliable, to a large extent because its funding and military
> commitment have been so stable. Can Europe's approach assure such
> stability? That the United States would switch off GPS signals is
> indeed a modern myth. Even were there such a technical ability --
> which there isn't -- it would be politically impossible.
>

Does anyone seriously think the US Government would turn GPS off and
completely cripple their military? Come on .. this is the military
machine that believes that technology is the answer to absolutely
everything. Turning off GPS would effectively make them blind and lost.

--
Regards

Steve G

Alan White

2007-06-19, 10:33 pm

On Tue, 19 Jun 2007 21:24:35 GMT, SteveG <_@_._> wrote:

>Does anyone seriously think the US Government would turn GPS off and
>completely cripple their military?

Well, the author of the bit that you've quoted obviously doesn't. He
says 'That the United States would switch off GPS signals is indeed a
modern myth.'.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

GSV Three Minds in a Can

2007-06-19, 10:33 pm

Bitstring <nQXdi.8252$p8.1244@text.news.blueyonder.co.uk>, from the
wonderful person SteveG <_@_._> said
>
>Does anyone seriously think the US Government would turn GPS off and
>completely cripple their military? Come on .. this is the military
>machine that believes that technology is the answer to absolutely
>everything. Turning off GPS would effectively make them blind and lost.

I guess you are too young to have heard of SA (Selective Availability)
then? The availability for (USA & allies) military use does not imply
the availability for all and sundry, terrorists included.

--
GSV Three Minds in a Can
8,963 Km walked. 1,746Km PROWs surveyed. 31.7% complete.

Happy Trails

2007-06-19, 10:33 pm

On Tue, 19 Jun 2007 22:44:50 +0100, Alan White
<alan.lesley@ukgateway.net> wrote:

>On Tue, 19 Jun 2007 21:24:35 GMT, SteveG <_@_._> wrote:
>
>
>Well, the author of the bit that you've quoted obviously doesn't. He
>says 'That the United States would switch off GPS signals is indeed a
>modern myth.'.

The reason he makes this statement, I believe, is because GPS has
become such an integral and vital part of so very many day to day
commercial functions, that to turn it off, even for a day, would cause
such a serious disruption to so many US owned industries world wide
that it is unthinkable that the oil cartels, shipping conglomerates,
agricultural and forestry management, North American survey and
construction industry, vehicle-based delivery systems, taxi and bus
fleets, airline navigation, and countless other smaller businesses
would allow this to happen.

The military has certain powers, but private enterprise is sacred in
America. And these days it runs on GPS.

Rudy P

2007-06-19, 10:33 pm

I think that free Galileo is also a myth. Last time I visited my old country
I had to pay for a piss. Nothing is free in Europe. Rudy.

"Happy Trails" <nomail@myplace.com> wrote in message
news:tdog73pjvre2ov8
ns6a9qvikoal7bt0cp4@
4ax.com...
> On Tue, 19 Jun 2007 22:44:50 +0100, Alan White
> <alan.lesley@ukgateway.net> wrote:
>
>
>
> The reason he makes this statement, I believe, is because GPS has
> become such an integral and vital part of so very many day to day
> commercial functions, that to turn it off, even for a day, would cause
> such a serious disruption to so many US owned industries world wide
> that it is unthinkable that the oil cartels, shipping conglomerates,
> agricultural and forestry management, North American survey and
> construction industry, vehicle-based delivery systems, taxi and bus
> fleets, airline navigation, and countless other smaller businesses
> would allow this to happen.
>
> The military has certain powers, but private enterprise is sacred in
> America. And these days it runs on GPS.
>

Alan White

2007-06-20, 4:33 am

On Tue, 19 Jun 2007 19:17:58 -0400, Happy Trails <nomail@myplace.com>
wrote:

>The reason he makes this statement, I believe, is because GPS has
>become such an integral and vital part of so very many day to day
>commercial functions, that to turn it off, even for a day, would cause
>such a serious disruption to so many US owned industries world wide
>that it is unthinkable that the oil cartels, shipping conglomerates,
>agricultural and forestry management, North American survey and
>construction industry, vehicle-based delivery systems, taxi and bus
>fleets, airline navigation, and countless other smaller businesses
>would allow this to happen.

I think you're absolutely right.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

SteveG

2007-06-20, 4:33 am

GSV Three Minds in a Can wrote:
> Bitstring <nQXdi.8252$p8.1244@text.news.blueyonder.co.uk>, from the
> wonderful person SteveG <_@_._> said
>
> I guess you are too young to have heard of SA (Selective Availability)
> then? The availability for (USA & allies) military use does not imply
> the availability for all and sundry, terrorists included.
>

I wish! I'm old enough to remember when the military - even the
Americans - navigated using maps and a compass or by taking star fixes.
The first sentence of the item I was commenting on says "switched off" -
as in not on at all - rather than selectively available by degrees. For
sure, they could reintroduce selective availability but lets face it
that would hardly cripple industry or commerce, as argued elsewhere in
this thread. It might make things less effective than they currently are
but that's all.

--
Regards

Steve G

Philip Green

2007-06-20, 4:33 am

In message <nQXdi.8252$p8.1244@text.news.blueyonder.co.uk>
SteveG <_@_._> wrote:

> Turning off GPS would effectively make them blind and lost.
>
>

Would that make all that much difference? They can hardly make a bigger mess
of the world than they're already doing.

--
Regards,
Philip.

SteveG

2007-06-20, 12:33 pm

Philip Green wrote:
> In message <nQXdi.8252$p8.1244@text.news.blueyonder.co.uk>
> SteveG <_@_._> wrote:
>
>
>
> Would that make all that much difference? They can hardly make a bigger mess
> of the world than they're already doing.
>
Touchee :-)

--
Regards

Steve G

Dale DePriest

2007-06-20, 3:33 pm

SteveG wrote:
> GSV Three Minds in a Can wrote:
>
> I wish! I'm old enough to remember when the military - even the
> Americans - navigated using maps and a compass or by taking star fixes.
> The first sentence of the item I was commenting on says "switched off" -
> as in not on at all - rather than selectively available by degrees. For
> sure, they could reintroduce selective availability but lets face it
> that would hardly cripple industry or commerce, as argued elsewhere in
> this thread. It might make things less effective than they currently are
> but that's all.
>
>
SA was a stop gap measure that is no longer needed at all thus there is
never any reason to turn it back on. Its original purpose is now served
much better by the replacement technologies that allow the blocking and
spoofing of gps in local areas of military campaign without having to
change anything in the GPS constellation.

SA will not return and GPS will not be turned off until Armageddon.

Dale
--
_ _ Dale DePriest
/`) _ // http://users.cwnet.com/dalede
o/_/ (_(_X_(` For GPS and GPS/PDAs

GSV Three Minds in a Can

2007-06-20, 3:33 pm

Bitstring < 137ipdh9o368se9@corp
.supernews.com>, from the wonderful
person Dale DePriest <Dale@gpsinformation.het> said
>
>
>SteveG wrote:
>SA was a stop gap measure that is no longer needed at all thus there is
>never any reason to turn it back on. Its original purpose is now served
>much better by the replacement technologies that allow the blocking and
>spoofing of gps in local areas of military campaign without having to
>change anything in the GPS constellation.
>
>SA will not return and GPS will not be turned off until Armageddon.

'blocking and spoofing' look pretty much like 'GPS turned off' to me -
why do you believe there is a useful distinction? The original comment
that the USA would be unable to turn off GPS for military reasons is
bunk .. they might be =unwilling= to turn it off, for commercial reasons
(where 'turn off' = SA, spoofing, blocking, or anything else which would
kill civilian apps like blind landing or whatever).

I =don't= say that this is a valid reason for proceeding with Gallileo,
Glosnast, or whatever, since those other governments are just as likely
to 'turn off' (in whatever fashion) their own systems for their own
reasons (except the Europeans would probably take 10 years to arrive at
the required decision).

c.f. The Internet .. of arguably less military significance, but equally
vulnerable to government tampering.

--
GSV Three Minds in a Can
8,963 Km walked. 1,746Km PROWs surveyed. 31.7% complete.

Dale DePriest

2007-06-20, 10:33 pm

GSV Three Minds in a Can wrote:
> Bitstring < 137ipdh9o368se9@corp
.supernews.com>, from the wonderful
> person Dale DePriest <Dale@gpsinformation.het> said
>
> 'blocking and spoofing' look pretty much like 'GPS turned off' to me -
> why do you believe there is a useful distinction? The original comment
> that the USA would be unable to turn off GPS for military reasons is
> bunk .. they might be =unwilling= to turn it off, for commercial reasons
> (where 'turn off' = SA, spoofing, blocking, or anything else which would
> kill civilian apps like blind landing or whatever).

Then you don't know how spoofing and blocking works. These are local
measures performed on the ground in a combat zone and do not effect the
satellites at all. The range of the interruption of service is local to
the area where the blocking is done and is quite different from turning
off GPS which has global impact. Note that the military will be fully
able to block or spoof Galileo as well when and if it ever gets operational.

Do you see the difference now?

Dale

--
_ _ Dale DePriest
/`) _ // http://users.cwnet.com/dalede
o/_/ (_(_X_(` For GPS and GPS/PDAs

GSV Three Minds in a Can

2007-06-20, 10:33 pm

Bitstring < 137j61psb1vj6da@corp
.supernews.com>, from the wonderful
person Dale DePriest <Dale@gpsinformation.het> said
>
>
>GSV Three Minds in a Can wrote:
[color=darkred]
>
>Then you don't know how spoofing and blocking works. These are local
>measures performed on the ground in a combat zone and do not effect the
>satellites at all. The range of the interruption of service is local to
>the area where the blocking is done and is quite different from turning
>off GPS which has global impact. Note that the military will be fully
>able to block or spoof Galileo as well when and if it ever gets operational.
>
>Do you see the difference now?

Not unless you are willing to define the maximum possible area of
'local', no. Afaict the effect is that the GPS service is not available
to (some) users .. that is 'turned off' in my book. Whether you do it at
the satellite, or from someplace else by broadcasting a counter signal,
the effect is no service. And since it is your satellite, nobody can
challenge your right to do so.

Do it to someone else's satellite system and you are undoubtedly in the
wrong. You appear to have rather a more restricted view of the meaning
of 'GPS turned off' than I do.

--
GSV Three Minds in a Can
8,963 Km walked. 1,746Km PROWs surveyed. 31.7% complete.

Alan White

2007-06-20, 10:33 pm

On Wed, 20 Jun 2007 22:38:33 +0100, GSV Three Minds in a Can
<GSV@quik.clara.co.uk> wrote:

>Not unless you are willing to define the maximum possible area of
>'local', no. Afaict the effect is that the GPS service is not available
>to (some) users .. that is 'turned off' in my book. Whether you do it at
>the satellite, or from someplace else by broadcasting a counter signal,
>the effect is no service. And since it is your satellite, nobody can
>challenge your right to do so.

The UK Ministry of Defence has announced a 'local blocking' of the GPS
signal covering a small area in, I think, Cornwall. I haven't the exact
details because I only keep posts for two days. The effect will only be
seen in a very small area, not globally. The 'blocking' will be carried
out by the MOD, not the US DOD, by transmitting a jamming signal on the
GPS frequency. The area to which it applies was fairly specific but
certainly not more than county-wide.

I live six hundred miles from Cornwall so it won't affect me or, if I'm
correct about where you live, you either. That to me is 'local'.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

Dale DePriest

2007-06-20, 10:33 pm

GSV Three Minds in a Can wrote:
> Bitstring < 137j61psb1vj6da@corp
.supernews.com>, from the wonderful
> person Dale DePriest <Dale@gpsinformation.het> said
>
>
> Not unless you are willing to define the maximum possible area of
> 'local', no. Afaict the effect is that the GPS service is not available
> to (some) users .. that is 'turned off' in my book. Whether you do it at
> the satellite, or from someplace else by broadcasting a counter signal,
> the effect is no service. And since it is your satellite, nobody can
> challenge your right to do so.
>
> Do it to someone else's satellite system and you are undoubtedly in the
> wrong. You appear to have rather a more restricted view of the meaning
> of 'GPS turned off' than I do.
>

Evidently. Turning off GPS is turning off like turning off your stove.
Blocking the heat from the stove is not the same as turning off the
stove. Blocking GPS signals is one of the techniques that is used in war
time but both sides if they can get away with it. Of course the US
military only blocks the civilian portion since their portion is
encrypted anyway. Whether this is right or wrong is beyond the point of
this discussion but you should be aware that the US has negotiated the
Galileo signals standards such that they can be blocked in a local area.

This local blocking is not what everyone else (besides you) means when
they say they are worried that the US will turn off the GPS system.

Dale
--
_ _ Dale DePriest
/`) _ // http://users.cwnet.com/dalede
o/_/ (_(_X_(` For GPS and GPS/PDAs

Happy Trails

2007-06-20, 10:33 pm

On Wed, 20 Jun 2007 22:38:33 +0100, GSV Three Minds in a Can
<GSV@quik.clara.co.uk> wrote:
>Bitstring < 137j61psb1vj6da@corp
.supernews.com>, from the wonderful
>person Dale DePriest <Dale@gpsinformation.het> said
[color=darkred]
[color=darkred]
>
>Do it to someone else's satellite system and you are undoubtedly in the
>wrong. You appear to have rather a more restricted view of the meaning
>of 'GPS turned off' than I do.

Now, now, boys, lets take a logical look at this.

Let's say, for arguments sake, the Americans are fighting against some
guys they refer to as terrorists somewhere in Africa.

They might decide to bugger up the civilian gps signals somehow so
they can see where they are, but their enemy cannot, in case the enemy
is using gps.

Do you really believe that they are NOT going to bugger up the signals
from ALL OTHER SATELLITE-based navigation systems that their enemy
might possibly use in that local area, just because maybe it wouldn't
be such a nice thing to do to the
Russians/Chinese/Eurowienies/whoever?

Especially if the French or somebody sold the enemy some missile
guidance systems that were not dependent on gps but rather on Galileo?

Really?

Now how does having Galileo as well as gps help in that situation?

So what happens to the "We need Galileo because the US might turn off
GPS" argument? Whatever the heck you might mean by "turn off"?

It's silly, right?

Can you really see a future George Bush, or even whoever his more
intelligent repplacement might be, saying, "Oh wait a minute, we can't
block Glonass here just because those terrorists are using weapons
they bought in Moscow!".

Rex

2007-06-21, 3:33 pm

Philip Green wrote:
> In message <nQXdi.8252$p8.1244@text.news.blueyonder.co.uk>
> SteveG <_@_._> wrote:
>
[color=darkred]
> Would that make all that much difference? They can hardly make a bigger mess
> of the world than they're already doing.

If it weren't for the U.S. military, you would not be enjoying your
GPS-based toys. And likely, not much else either.

Credit were credit is due.

SteveG

2007-06-21, 10:33 pm

Rex wrote:
> Philip Green wrote:
>
>
> If it weren't for the U.S. military, you would not be enjoying your
> GPS-based toys. And likely, not much else either.
>
> Credit were credit is due.

Credit for what? Making the world a safer place?

--
Regards

Steve G

Jack Erbes

2007-06-21, 10:33 pm

SteveG wrote:
<snip>
>
> Credit for what? Making the world a safer place?

Have you ever heard of DARPANET? That was the Defense Advanced Research
Projects Administration (DARPA) Net and it became the Internet.

Jack

Phil Wheeler

2007-06-21, 10:33 pm

Jack Erbes wrote:
> SteveG wrote:
> <snip>
>
> Have you ever heard of DARPANET? That was the Defense Advanced Research
> Projects Administration (DARPA) Net and it became the Internet.
>
> Jack

I think it was originally the ARPANET, back before
they hung Defense on the front of the name.

Phil

Jack Erbes

2007-06-21, 10:33 pm

Phil Wheeler wrote:
> Jack Erbes wrote:
>
>
> I think it was originally the ARPANET, back before they hung Defense on
> the front of the name.
>

You're probably right. The agency was called ARPA, then DARPA, then
ARPA again. The net was called DARPANET when I first encountered it in
the Navy and that has stayed that way in my mind.

Jack

Rex

2007-06-22, 12:33 pm

Jack Erbes wrote:
> Phil Wheeler wrote:
>
> You're probably right. The agency was called ARPA, then DARPA, then
> ARPA again. The net was called DARPANET when I first encountered it in
> the Navy and that has stayed that way in my mind.

OK, so without the U.S. Military you would not have the Internet nor GPS
satellites. This would be a pretty quiet forum, wouldn't it?

For that matter, can you image any other nation on earth, having spent
billions for an exclusive military worldwide positioning system, then
opening that up for the entire world to use, free of charge?
Never happen.

GSV Three Minds in a Can

2007-06-26, 10:33 pm

Bitstring < 819j73hujs53hhhcnajr
jprr88o87on86h@4ax.com>, from the
wonderful person Alan White <alan.lesley@ukgateway.net> said
>On Wed, 20 Jun 2007 22:38:33 +0100, GSV Three Minds in a Can
><GSV@quik.clara.co.uk> wrote:
>
>
>The UK Ministry of Defence has announced a 'local blocking' of the GPS
>signal covering a small area in, I think, Cornwall. I haven't the exact
>details because I only keep posts for two days. The effect will only be
>seen in a very small area, not globally. The 'blocking' will be carried
>out by the MOD, not the US DOD, by transmitting a jamming signal on the
>GPS frequency. The area to which it applies was fairly specific but
>certainly not more than county-wide.

The question was not how =small= an area, but how =large= the area could
be. I did say 'define the maximum possible area of local'. If the area
can be made as large as France, or 'Europe', then the end result is the
same for most users as 'turning GPS signal off'.

And I say again, this is no reason to have Galileo, but don't go telling
me 'it is technically impossible for the USA to turn GPS off', or even
'it is politically impossible'.

--
GSV Three Minds in a Can
8,963 Km walked. 1,746Km PROWs surveyed. 31.7% complete.

Jeff

2007-06-26, 10:33 pm

GSV Three Minds in a Can wrote:[color=darkred
]

The full story is at:
http://www.theregister.co.uk/2007/0... /> l_cornwall/

Article begins:

"UK gov defence boffins will carry out GPS-jamming trials in Cornwall
today and tomorrow.

Jamming transmissions will be made at the Portreath MoD site, a remote
radar station operated by the RAF's Air Surveillance and Control Systems
Force Command. The old airfield was once used (low down on page) as an
outstation of the former Chemical Defence Establishment, headquartered
at Porton Down.

Ministry of Defence (MoD) scientific operations are nowadays
consolidated under the Defence Science and Technology Laboratory (DSTL),
and it's these boffins who will carry out the tests this week.

According to a BBC report, effects on GPS receivers can be expected up
to 11km from Portreath, which would include the local towns Camborne and
Redruth. Apparently, local emergency and rescue services have been
warned, and arrangements are in place to cancel the trials if necessary."

Remainder is at the quoted URL

Happy Trails

2007-06-26, 10:33 pm

On Wed, 27 Jun 2007 00:26:31 +0100, GSV Three Minds in a Can
<GSV@quik.clara.co.uk> wrote:

>The question was not how =small= an area, but how =large= the area could
>be. I did say 'define the maximum possible area of local'. If the area
>can be made as large as France, or 'Europe', then the end result is the
>same for most users as 'turning GPS signal off'.
>
>And I say again, this is no reason to have Galileo, but don't go telling
>me 'it is technically impossible for the USA to turn GPS off', or even
>'it is politically impossible'.

C'mon, dumbhead. GPS works by satellites transmitting signals. They
are not "directional". Any given satellite can be made to send a good
signal or a bad signal for all or maybe some part of its orbit. To
block out coverage for, as you say, France for example, the signals
would have to be screwed around with for any satellite that is
viewable at any useful elevation angle - say above 5 degrees (maybe)
from anywhere in France. This would render GPS coverage pretty flakey
for a very large number of countries within thousands of miles of
France, especially to the north where fewer sats would be in view.

I do not know the details of such control, but I'd suspect, in
addition to the silliness above, that any turning on/off of
transmission, or clock diddling, or whatever other method of
disruption, could probably only be applied from one of the ground
control stations, and probably only to be effective immediately, not
preprogrammed for some future time period. Again I say I don't know,
but this is what I suspect.

So how precise could this be if it could only be done when the sat is
reachable from one of these stations. Maybe it covers the whole globe
and the whole constellation at all times - dunno.

If you are actually wondering what is the maximum area of local
jamming from ground or airborne sources, it's like, how many jamming
transmitters do you want operate, and how powerful? It's open ended!

Sam Wormley

2007-06-26, 10:33 pm

Happy Trails

2007-06-27, 7:33 am

On Wed, 27 Jun 2007 08:33:05 +0100, Alan White
<alan.lesley@ukgateway.net> wrote:

>On Tue, 26 Jun 2007 20:46:03 -0400, Happy Trails <nomail@myplace.com>
>wrote:
>
>
>Not so. I've received twelve sats at about 71°N. Because of their
>orbital radius, as you goes further north satellites 'over the horizon'
>become visible. The latitude for receiving least satellites is about
>45°N in the northern hemisphere.

Thanks, Alan. Most of my work in the past has been around the equator
+/- 15°.

Do the rest of my ramblings sound about right? I really can't be
bothered doing any "research" on this somewhat frivolous topic.

It seems odd that the " least satellites" band would be very close to
a large part of the continental USA. I guess they thought if their
ships were in port, they already knew where they were. Or maybe
they're trying to shaft the Canadians once again, hahaha.

- Tom

Alan White

2007-06-27, 7:33 am

On Tue, 26 Jun 2007 20:46:03 -0400, Happy Trails <nomail@myplace.com>
wrote:

> ...especially to the north where fewer sats would be in view.

Not so. I've received twelve sats at about 71°N. Because of their
orbital radius, as you goes further north satellites 'over the horizon'
become visible. The latitude for receiving least satellites is about
45°N in the northern hemisphere.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

Alan White

2007-06-27, 7:33 am

On Wed, 27 Jun 2007 06:53:26 -0400, Happy Trails <nomail@myplace.com>
wrote:

>Thanks, Alan. Most of my work in the past has been around the equator
>+/- 15°.
>

:-)

>Do the rest of my ramblings sound about right? I really can't be
>bothered doing any "research" on this somewhat frivolous topic.
>

More or less :-) The trouble is that GPSr ownership has stopped being a
'niche' and has become so widespread that it's very difficult to dispel
the myths. If the myths aren't dispelled they very quickly become
'facts'.

>It seems odd that the " least satellites" band would be very close to
>a large part of the continental USA. I guess they thought if their
>ships were in port, they already knew where they were. Or maybe
>they're trying to shaft the Canadians once again, hahaha.

If you can see four sats you can get a reasonable fix. It's all
compromise - like life.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

GSV Three Minds in a Can

2007-06-27, 10:33 am

Bitstring < pfc3839i707p8ctgogb1
urkt0f6o2u4jvl@4ax.com>, from the
wonderful person Happy Trails <nomail@myplace.com> said
>On Wed, 27 Jun 2007 00:26:31 +0100, GSV Three Minds in a Can
><GSV@quik.clara.co.uk> wrote:
>
>
>
>C'mon, dumbhead. GPS works by satellites transmitting signals. They
>are not "directional". Any given satellite can be made to send a good
>signal or a bad signal for all or maybe some part of its orbit. To
>block out coverage for, as you say, France for example, the signals
>would have to be screwed around with for any satellite that is
>viewable at any useful elevation angle - say above 5 degrees (maybe)
>from anywhere in France. This would render GPS coverage pretty flakey
>for a very large number of countries within thousands of miles of
>France, especially to the north where fewer sats would be in view.

Therefore (dumbhead), as I said, it is possible to 'turn off' GPS (for
non military users) over the whole planet. Q.E.D. By sending a bad (non
military) signal. It might still be politically unacceptable, but it
ain't technically impossible, as someone claimed. It WAS done during the
era of SA (for a value of 'turned off' which meant 'you can't have an
accurate signal, as required for blind landing systems').

--
GSV Three Minds in a Can
8,963 Km walked. 1,746Km PROWs surveyed. 31.7% complete.

Alan White

2007-06-27, 10:33 am

On Wed, 27 Jun 2007 14:59:09 +0100, GSV Three Minds in a Can
<GSV@quik.clara.co.uk> wrote:

>Therefore (dumbhead), as I said, it is possible to 'turn off' GPS (for
>non military users) over the whole planet. Q.E.D. By sending a bad (non
>military) signal. It might still be politically unacceptable, but it
>ain't technically impossible, as someone claimed.

I don't have the relevant posts (I only archive 48 hours-worth) but what
is usually claimed is that GPS coverage can be turned off over a small
are. That isn't possible. GPS coverage can be jammed over a small area
which is a different matter.

If you interpret 'jamming' as 'switching off' we must agree to disagree.

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

GSV Three Minds in a Can

2007-06-27, 12:33 pm

Bitstring < 0lu4839e8q6i4il4kmce
e6gmk7h0hbems1@4ax.com>, from the
wonderful person Alan White <alan.lesley@ukgateway.net> said
>On Wed, 27 Jun 2007 14:59:09 +0100, GSV Three Minds in a Can
><GSV@quik.clara.co.uk> wrote:
>
>
>I don't have the relevant posts (I only archive 48 hours-worth) but what
>is usually claimed is that GPS coverage can be turned off over a small
>are. That isn't possible. GPS coverage can be jammed over a small area
>which is a different matter.
>
>If you interpret 'jamming' as 'switching off' we must agree to disagree.

Nope, what I was disagreeing with/commenting on was way back upthread
where someone (lost in the mists of time) said:
[color=darkred]
machine that >>>believes that technology is the answer to absolutely
everything. Turning off GPS >>>would effectively make them blind and
lost.

My point was that the US government can 'turn off' GPS for civilian
users (by any of several means) without touching the military users.
They used to do so (for some SA value of 'turned off'). The technical
ability exists. Politically it would be a hot potato, but hey, that
didn't stop Iraq, Panama, Grenada, etc. etc. did it.

I do NOT believe that is a good excuse for alternate systems, since I'm
not sure a) anyone else is any more trustworthy, up to and including the
UN, b) the USA can be trusted not to 'turn off' someone else's GPS
system if they feel like it (although that would be an act of war). But
don't tell me the current GPS can't (technically) be 'turned off'
(worldwide) or jammed/spoofed/blocked (over whatever area you choose) by
the USA, probably quite legally.

--
GSV Three Minds in a Can
8,963 Km walked. 1,746Km PROWs surveyed. 31.7% complete.

Alan White

2007-06-27, 12:33 pm

On Wed, 27 Jun 2007 17:05:14 +0100, GSV Three Minds in a Can
<GSV@quik.clara.co.uk> wrote:

>I do NOT believe that is a good excuse for alternate systems, since I'm
>not sure a) anyone else is any more trustworthy, up to and including the
>UN, b) the USA can be trusted not to 'turn off' someone else's GPS
>system if they feel like it (although that would be an act of war).

In a nutshell, I also think Galileo is a complete waste of time and
money.

>But don't tell me the current GPS can't (technically) be 'turned off'
>(worldwide) or jammed/spoofed/blocked (over whatever area you choose) by
>the USA, probably quite legally.

I wouldn't dare :-)

--
Alan White
Mozilla Firefox and Forte Agent.
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Webcam and weather:- http://windycroft.gt-britain.co.uk/weather

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