Having read the responses to and comments on my original post, I am
still left with a few questions:

If I am on the Bahama Bank or in the Bahamian Exumas or in Hawk Channel
off Key Largo or in a bay or "river" or "creek" off the Chesapeake Bay,
negotiating shoals on a cloudy and windy day and GPS goes out because
it was suddenly turned off, is that not an "end" for me?

Does anyone believe or expect GPS to be turned off only for a few
minutes or hours? I would expect weeks to months, or longer, of "ended"
signals.

And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

wrote in message
ups.com...
having GPS suddenly go off? This may well be an "end."


Not the "end" if you maintain a proper watch and can still remember how to
navigate, using traditional methods we used before GPS.

I don't mean reverting to Celestial, just maintain your plot/log and use DR
until your obtain a position fix using other basic methods.

Of my 48 years of boating, only in the last 2 years have I had
GPS/Loran/digital charts. I will admit that I find GPS and digital charts
very accurate and convenient, to the extent that I frequently neglect to
maintain my plot. However, last summer I was reminded the hard way, when the
power failed to my nav station while I was negotiating (for the first time)
the tricky Hammersley Inlet (So. Puget Sound). With 6-8 knot current
running, there was little time to take bearings and plot position. In this
case, I relied on the "ole MK I Eyeball" and description provided in my
cruising guide (shoreline references, etc.).

IMHO, a brief loss (day/month or so) shouldn't be the ended of recreational
boating. Just an opportunity to employ the traditional methods we all should
be familiar with.

My opinion, FWIW.

Steve
s/v Good Intentions

Any book or reference on boating safety and navigation will tell the prudent
mariner to NEVER depend on only one source of information for navigation....

I flew an airplane around Alaska in the 60's without a GPS or a VOR. We
used sectionals (which had large "uncharted areas) and pilotage (DR).
Sailed the windward, leeward, virgin islands and Bahamas in the 90's
without a GPS. Used charts, compass, knowledge of tides and currents,
coast pilot, dr and guide books. Never had a GPS until about three years
ago. Turning GPS off will not make all planes crash and ships run
aground. Learn how to navigate!.
krj

wrote:

Having read the responses to and comments on my original post, I am
still left with a few questions:

If I am on the Bahama Bank or in the Bahamian Exumas or in Hawk Channel
off Key Largo or in a bay or "river" or "creek" off the Chesapeake Bay,
negotiating shoals on a cloudy and windy day and GPS goes out because
it was suddenly turned off, is that not an "end" for me?

Does anyone believe or expect GPS to be turned off only for a few
minutes or hours? I would expect weeks to months, or longer, of "ended"
signals.

And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

wrote:
Having read the responses to and comments on my original post, I am
still left with a few questions:

If I am on the Bahama Bank or in the Bahamian Exumas or in Hawk Channel
off Key Largo or in a bay or "river" or "creek" off the Chesapeake Bay,
negotiating shoals on a cloudy and windy day and GPS goes out because
it was suddenly turned off, is that not an "end" for me?

Yes. I suggest you stay off the water. Those of us who know how to
navigate without GPS will thank you.

Does anyone believe or expect GPS to be turned off only for a few
minutes or hours? I would expect weeks to months, or longer, of "ended"
signals.

Actually, its most likely it will be degraded in some locality. It can
be made useless for terrorists by degrading the altitude component.


And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

Commercial flights do not rely on GPS for approaches.

"Jeff Morris" wrote in message
...
wrote:
Having read the responses to and comments on my original post, I am
still left with a few questions:

If I am on the Bahama Bank or in the Bahamian Exumas or in Hawk Channel
off Key Largo or in a bay or "river" or "creek" off the Chesapeake Bay,
negotiating shoals on a cloudy and windy day and GPS goes out because
it was suddenly turned off, is that not an "end" for me?

Yes. I suggest you stay off the water. Those of us who know how to
navigate without GPS will thank you.

Does anyone believe or expect GPS to be turned off only for a few
minutes or hours? I would expect weeks to months, or longer, of "ended"
signals.

Actually, its most likely it will be degraded in some locality. It can be
made useless for terrorists by degrading the altitude component.


And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

Commercial flights do not rely on GPS for approaches.

There are certain procedures available with GPS that are impractical (or
even undoable) for other navigation techniques. For instance I have made
dark and stormy approaches to a couple of harbors that I would not have done
without GPS and radar. These are comfortable with GPS with radar as a
backup and sometimes a calibrator. I would not attempt these by radar
alone.

Note that lights and other aids to navigation are being retired. In a few
years it will be impractical to sail a lot of places without GPS.

Aircraft use of GPS provides very quick problem detection. Implemented in
WAAS it provides an indication of non-proper operation in seconds.
Commercial airplanes certainly fly GPS approaches. I don't think there are
any precision approaches flown GPS yet...but non-precision approaches
certainly are. Eventually it is likely that the VOR/DME system and the ILS
will give way to GPS.

We are busily embedding GPS into the fabric of society. It is very
unlikely that the gov. will suspend the system at all...if they must it
will likely be for rather short periods of time.

Jim Donohue

On 20 Dec 2004 07:58:48 -0800, wrote:

Having read the responses to and comments on my original post, I am
still left with a few questions:

If I am on the Bahama Bank or in the Bahamian Exumas or in Hawk Channel
off Key Largo or in a bay or "river" or "creek" off the Chesapeake Bay,
negotiating shoals on a cloudy and windy day and GPS goes out because
it was suddenly turned off, is that not an "end" for me?


You reference to the Bahamas reminded me of a epsilon in the Sea of
Abaco in 1992. We were in our way back from a visit to Green Turtle
Cay. We were approaching the Whale Key Passage, about to go out into
the Atlantic and then back into the Abacos. Ahead of us were two
sailboats about to do the same. One had a stopped. The other radioed
him and asked if he was coming through. he responded that his GPS
had failed and he did not know where he was. All he had to do was
look around use his chart.


Does anyone believe or expect GPS to be turned off only for a few
minutes or hours? I would expect weeks to months, or longer, of "ended"
signals.

GPS will not be turned off world wide. It may be turned off in areas
of conflict. GMDSS is closely integrated with GPS. Turning off GPS
would endanger lives.


And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

Commercial airline pilot rely on radio navigation beacons and flight
controllers to stay in their assigned air space. Instrument landings
also use radio beacons.

I would suggest that EVERYONE take a coastal navigation course. You
still have to understand tides and currents, chart symbols, compass
reading, plotting, the buoyage system, and position finding.

Jack

__________________________________________________
Jack Dale
Swiftsure Sailing Academy
Director/ISPA and CYA Instructor
http://www.swiftsuresailing.com
__________________________________________________

"Steven Shelikoff" wrote in message
...
On 20 Dec 2004 07:58:48 -0800, wrote:


It does get locally turned off once in a while for tests, military
exercises, etc. Usually they give plenty of warning. For instance,
here's an AP line about an outage back in June for the Carolinas to
Florida:
----------
Military testing system designed to jam GPS signals off coast

WILMINGTON, N.C. (AP) - Military officials are testing a system for
jamming signals from navigational satellites - an experiment that could
disable boaters' GPS devices and force them to rely on dead reckoning.
The test began Friday and will run through June 20, as part of a NATO
training exercise along the Atlantic Coast.

The Coast Guard said GPS signals will be unreliable or unavailable in
waters up to 60 miles off North Carolina and along the coast of northern
and central Florida. Officials said the testing may affect cell phones
as well as GPS navigation devices in boats, airplanes or cars.

Coast Guard stations are trying to get word out about the interference.

"What we kind of foresee happening is some confusion on the mariners'
end," said Petty Officer 1st Class David Christensen.
----------

And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

No, that won't be the end either... unless the plane doesn't have a
pilot and it's being flown automatically, directed by GPS.

Steve

Actually Steve I think the military jammed the signal rather than turning it
off or degrading it. I also believe that there are antennas that would make
it difficult or impossible to jam a GPS particularly from a boat a few miles
away from the jamming site. I doubt the military will talk about it but
reasonably simple shielded antenna with deliberate limitation of the sky
viewed can probably provide pretty good reception even in the face of heavy
jamming.

On the other side jamming GPS in a relatively close in situation like a
harbor or a city is a piece of cake. I am sure the hacker community already
has a couple of desings on the internet.

None of this in any way applies that the gov can't easily screw around with
the signal to any desired extent. I would also point out it would be
relatively trivial for the gov to take out Russian or European sattellites
as well. Probably construable as an act of war but why else would the gov.
do it?
Jim Donohue

Jim Donohue wrote:
"Steven Shelikoff" wrote in message
...

On 20 Dec 2004 07:58:48 -0800, wrote:


It does get locally turned off once in a while for tests, military
exercises, etc. Usually they give plenty of warning. For instance,
here's an AP line about an outage back in June for the Carolinas to
Florida:
----------
Military testing system designed to jam GPS signals off coast

WILMINGTON, N.C. (AP) - Military officials are testing a system for
jamming signals from navigational satellites - an experiment that could
disable boaters' GPS devices and force them to rely on dead reckoning.
The test began Friday and will run through June 20, as part of a NATO
training exercise along the Atlantic Coast.

The Coast Guard said GPS signals will be unreliable or unavailable in
waters up to 60 miles off North Carolina and along the coast of northern
and central Florida. Officials said the testing may affect cell phones
as well as GPS navigation devices in boats, airplanes or cars.

Coast Guard stations are trying to get word out about the interference.

"What we kind of foresee happening is some confusion on the mariners'
end," said Petty Officer 1st Class David Christensen.
----------


And mo Would anyone want to be in a commercial or private airplane
when making an initial approach in low ceiling weather to landing and
having GPS suddenly go off? This may well be an "end."

No, that won't be the end either... unless the plane doesn't have a
pilot and it's being flown automatically, directed by GPS.

Steve


Actually Steve I think the military jammed the signal rather than turning it
off or degrading it. I also believe that there are antennas that would make

Right. That's what the article says, that the military was jamming GPS
signals from 60 miles off North Carolina and along the coast of northern
and central Florida. Of course, it doesn't really matter why it's
unusable ... whether it's jammed or turned off, it's still unusable.

it difficult or impossible to jam a GPS particularly from a boat a few miles
away from the jamming site. I doubt the military will talk about it but

If you increase "few" miles to a hundred miles or more, I'd agree. That
also depends on how they jam it. I.e., whether it's from the air or
ground. You can possibly get directional antennas and point the null in
the direction of the jammer. But that assumes there's only one and that
it's not somewhere above you. There's also ways of decreasing the
effectiveness of a jammer via signal processing. Of course, most
boaters don't go out equipped to handle possible jamming.

reasonably simple shielded antenna with deliberate limitation of the sky
viewed can probably provide pretty good reception even in the face of heavy
jamming.

It's got to be a little better than that. It has to have a pretty good
null specifically in the direct of the jammer. That's because GPS
signals are so weak (actually, they're below the level of background
noise and signal processing is needed to dig them out) that just about
any interference can cover them up.

On the other side jamming GPS in a relatively close in situation like a
harbor or a city is a piece of cake. I am sure the hacker community already
has a couple of desings on the internet.

You want a link? I've seen several make your own designs, complete with
schematics and parts lists with sources, design considerations, etc. To
take out GPS up to maybe 50 miles or more you only need about 4 watts
ERP, same as a CB walkie talkie. If you're equipped to handle the
jamming, you can overcome that and limit the range of the jammer to
maybe only a few miles. But again, most boaters aren't equipped to deal
with jamming and it would render the GPS of most boaters useless.

None of this in any way applies that the gov can't easily screw around with
the signal to any desired extent. I would also point out it would be
relatively trivial for the gov to take out Russian or European sattellites
as well. Probably construable as an act of war but why else would the gov.
do it?

It's just as trivial for another sophisticated government, one with
space capability, to take out our GPS satellites. Also probably an act
of war.

Steve

In a message dated 12/20/2004 1:43:11 PM Eastern Standard Time,
writes:
How many boats have you been on in the past five or so years that have
on their nav table: a divider, a chart ruler, or anything like these
simple and other nav instruments? I would guess you have found very
few, indeed if any.

Ahoy:

I have to admit that (1) my boat does have a nav table, dividers, and other
simple chart plotting tools, and that (2) I hardly ever use them.... I'm not
sure what other boater friends of mine have, but you've peaked my curiousity to
find out. Having said all this, I also agree that most of us do, in fact,
depend on the GPS alone more often than not. But if you are like me, I also
have something of an "eyeball DR" going on in my head almost all of the time.
This served me well once when I was navigating a course on the GPS to a distant
marker. At some point, the "eyeball DR" in my brain kicked in to say that what
I was seeing did not look right. I was way off course. It turned out that I
had transposed the waypoints for my destination when I loaded them into my
GPS....It was an interesting lesson that happily ended well

Good sailing to you.

w.