waynes said ...
There is no viable alternative offshore other than celestial,
and even the Navy has stopped teaching it.

waynes i'm guessing that you mean that the navy doesn't teach RDF, not
that they don't teach celestial. only reason i say that is because it
seems like the military would need backups like celestial because i
understood that the EMP from a nuclear weapons blast could take out
electronics such as GPS systems. is that wrong ? i'm surprised that
someone in the navy who was going to navigate such important ships
would be able to get out of their training without knowing absolutely
every way there was in the world to navigate. it seems like a navy
sailor would have to know everything there is to know about navigation
before they could make decisions that affect the ship.

da kine said ...
GPS is great right up until you get a lighting strike and
everything blows out.

thanks da kine and everyone for the great posts. i want to know as
much about navigation as i can and really enjoy learning about all
these alternatives. you mentioned some others including cloud
formation, wind direction, wave intervals, etc, and i hope things like
that get mentioned in the two fat navigation books i'm currently
reading.

i wonder what other situations could lead to GPS not working ? i'm
with everyone else who thinks that GPS with some spares is really
important. i agree relying on just a GPS wired into the boat is a bad
idea because what happens if it stops working, or if your boat
batteries die, or you just forget to bring enough fuses or something,
or your power generation methods fail. i can't really think of much
that would stop a handheld unit from working except for
losing/destroying them, not having batteries, etc. i wonder what
situations outside of a sailors control could make GPS fail ? i mean,
i assume because so many people rely on GPS that the military wouldn't
just shut it off unless there was some really drastic reason for doing
so. i've read that they might make it more inaccurate or shut it off
in the event of war, would they ? and i assume too that they take
really good care of it since they and everyone relies on it so much ...
has it ever failed ?

As I understand it, they actually run off of a gyro system that is
better then GPS. Also, I have a good friend that captains a navy sub
that told me celestial navigation was required.

In your reading, pick up a red/orange colored paperback called
“Emergency Navigation�. Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won’t find
much of the good stuff in most books.

As for something else making GPS not work, there are a few things I
have come across and here they are.

On 9/11 GPS was scrabbled in many areas. For anyone in a critical
position in one of the scrabbled areas, OOPS!

In Mexico (and I love this one) I ran across and “electrical
engineer� that had a broken GPS and his spare didn’t work either.
This was a while back but … Turned out to be a bad antenna that I
fixed for him – the engineer☺

That’s the only way gps failures other then lighting that I know of.

As for a spare GPS, the rumor is that if you wrap a handheld in tinfoil
and get hit by lightning, your spare will still work. I don’t know
anyone that has put it to the test but I keep my spare wrapped just the
same.

GPS signals use to be scrabbled all the time. In about 1991 or so the
military started allowing public access of the gps signal. In times of
heightened defense alerts, the gps signal does get less accurate but
then there is also a differential signal that I don’t know much about
but is used to help the gps become more accurate again. All in all,
I’m more worried about lightning, having been through enough of it,
then anything else.

Da Kine wrote:
[snip]
In your reading, pick up a red/orange colored paperback called
"Emergency Navigation". Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won't find
much of the good stuff in most books.

good stuff, i will check into it ...

As for something else making GPS not work, there are a few things I
have come across and here they are.

i spent a little while reading about this since my last post and found
some interesting things i didn't know, i'll post some of them here
since you are interested too! from some of the things i read it looks
like GPS does/has failed before, i didn't know that before now.
there's a quote in one of these documents that i found interest, the
document says the quote is from "Interagency GPS Executive Board. GPS
policy, applications, modernization, international cooperation.
February 01". here's what it says ...

"GPS provides many benefits to civilian users. It is vulnerable,
however, to interference and other disruptions that can have harmful
consequences. GPS users must ensure that adequate independent backup
systems or procedures can be used when needed."

then later in that same document it is talking about situations where
GPS doesn't work, and apparently it's pretty easy to make it not work!
you can build GPS jammers using plans on the net to jam GPS signals,
and there are even jammers sold for doing the same thing. one paper i
read said that these jammers are sold to militaries that want to be
able to selectively jam areas for security reasons, and to defend
themselves from attack, and that some of these jammers are huge like
radio stations.

this one paper i read had these real world situations where GPS had
failed ...

"Jamming in Mesa, AZ
13 - 18 Dec 01, GPS jammer caused GPS failures within 180nm of Mesa,
AZ
Boeing was preparing for upcoming test
Accidentally left Jammer on L1 frequency radiating at .8mW
Jammer operated continuously for 4.5 days
Impact to ATC operations
A/C lost GPS 45nm from PHX, performed 35° turn toward traffic
NOTAM was not issued until 2nd day
Numerous pilots reported loss of GPS NavAid
Reports of hand-held GPS receivers not working"

"Jamming in Moss Landing Harbor, CA
15 Apr 01 - 22 May 01, VHF/UHF television antenna with pre-amplifier
caused GPS failures to all of Moss Landing Harbor
Boat owner purchased TV antenna, which was equipped with pre-amp
From interior location Amp's emitter jammed all of Moss Harbor and
1km out to sea
No GPS in entire area = 37 days
Impact to Moss Harbor
Research vessels relied heavily on timing from GPS
Extreme difficulty going through harbor in foggy conditions
Notification to all vessels in area that GPS was down
Switched back to radar control for harbor entrances"

the source for those was a document from a search engine with the title
"Civilian GPS Systems and Potential Vulnerabilities"

i also read online that geomagnetic storms can cause GPS to fail,
especially in higher latitudes and during periods of intense solar
activity. it said that storms can introduce errors of 1km and more
depending on location and how active the ionosphere is. and then there
are other kinds of errors too that i read about, ones that seem well
known to people who are really into that kind of thing.

thinking back on it, i also remember another reference to GPS failure,
somewhere in the red sea or east coast of africa there was a harbor
where GPS doesn't work, but now i can't remember where i read it. i
think it may have been in jimmy cornell's "world cruising handbook" but
i glanced through it just now and couldn't find the reference.
apologies to the author if i am wrong about that!

i guess like anything else, GPS is just another aide to navigation.

These are great examples of why I keep up on my other nav skills and
why I make a point to bust the chops of the guys that try to preach gps
like they do.

As well intentioned as people are, they are blindly falling into a trap
and leading others with them when they set aside the old world skills
of navigation.

Good for you for being smart!

purple_stars wrote:
Da Kine wrote:
[snip]

In your reading, pick up a red/orange colored paperback called
"Emergency Navigation". Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won't find
much of the good stuff in most books.


good stuff, i will check into it ...


As for something else making GPS not work, there are a few things I
have come across and here they are.


i spent a little while reading about this since my last post and found
some interesting things i didn't know, i'll post some of them here
since you are interested too! from some of the things i read it looks
like GPS does/has failed before, i didn't know that before now.
there's a quote in one of these documents that i found interest, the
document says the quote is from "Interagency GPS Executive Board. GPS
policy, applications, modernization, international cooperation.
February 01". here's what it says ...

"GPS provides many benefits to civilian users. It is vulnerable,
however, to interference and other disruptions that can have harmful
consequences. GPS users must ensure that adequate independent backup
systems or procedures can be used when needed."

then later in that same document it is talking about situations where
GPS doesn't work, and apparently it's pretty easy to make it not work!
you can build GPS jammers using plans on the net to jam GPS signals,
and there are even jammers sold for doing the same thing. one paper i
read said that these jammers are sold to militaries that want to be
able to selectively jam areas for security reasons, and to defend
themselves from attack, and that some of these jammers are huge like
radio stations.

this one paper i read had these real world situations where GPS had
failed ...

"Jamming in Mesa, AZ
13 - 18 Dec 01, GPS jammer caused GPS failures within 180nm of Mesa,
AZ
Boeing was preparing for upcoming test
Accidentally left Jammer on L1 frequency radiating at .8mW
Jammer operated continuously for 4.5 days
Impact to ATC operations
A/C lost GPS 45nm from PHX, performed 35° turn toward traffic
NOTAM was not issued until 2nd day
Numerous pilots reported loss of GPS NavAid
Reports of hand-held GPS receivers not working"

"Jamming in Moss Landing Harbor, CA
15 Apr 01 - 22 May 01, VHF/UHF television antenna with pre-amplifier
caused GPS failures to all of Moss Landing Harbor
Boat owner purchased TV antenna, which was equipped with pre-amp
From interior location Amp's emitter jammed all of Moss Harbor and
1km out to sea
No GPS in entire area = 37 days
Impact to Moss Harbor
Research vessels relied heavily on timing from GPS
Extreme difficulty going through harbor in foggy conditions
Notification to all vessels in area that GPS was down
Switched back to radar control for harbor entrances"

The jamming of GPS is possible and used. The challenge is long range
jamming or continuous jamming. It takes a great deal of power to jam a
GPS that is any distance away. It also needs to run continuously to
really screw you up. Once the jamming stops, or you get too far away,
it just locks back on. The jamming will likely be obvious. You just
won't get a signal. The better way of doing it is not jamming but
deceiving the GPS so it looks like it is working but leads you (or a
missile) away from the intended destination or target. This would be
fairly obvious on a yacht at sea.

In other words, don't worry about it. The 90% of the time you are on
your boat sitting at anchor it won't matter. The rest of the time
nobody cares to jam you.

Don't forget that tinfoil in your ball cap.

Gary wrote:
[snip]
The jamming of GPS is possible and used. The challenge is long range
jamming or continuous jamming. It takes a great deal of power to jam a
GPS that is any distance away. It also needs to run continuously to
really screw you up. Once the jamming stops, or you get too far away,
it just locks back on. The jamming will likely be obvious. You just
won't get a signal. The better way of doing it is not jamming but
deceiving the GPS so it looks like it is working but leads you (or a
missile) away from the intended destination or target. This would be
fairly obvious on a yacht at sea.

In other words, don't worry about it. The 90% of the time you are on
your boat sitting at anchor it won't matter. The rest of the time
nobody cares to jam you.

i never said i was worried about it. i never said i thought anyone was
going to jam me. i never said i was going to high latitudes where i
thought geomagnetic storms would affect me. all i did was answer my
own question which was "can GPS fail ?". to my surprise, yeah, there
were some cases where it has failed. end of story.

GPS is a great tool, my primary navigation tool and i would assume the
primary navigation tool of anyone on a boat. i can't imagine any
reasonable situation where it would ever fail for me. but that doesn't
make understanding when it can fail some kind of crime, it doesn't make
me into some kind of anti-GPS zealot.

Don't forget that tinfoil in your ball cap.

i don't understand why you are being rude to me, i've not done anything
to you.

purple_stars wrote:
Gary wrote:
[snip]

The jamming of GPS is possible and used. The challenge is long range
jamming or continuous jamming. It takes a great deal of power to jam a
GPS that is any distance away. It also needs to run continuously to
really screw you up. Once the jamming stops, or you get too far away,
it just locks back on. The jamming will likely be obvious. You just
won't get a signal. The better way of doing it is not jamming but
deceiving the GPS so it looks like it is working but leads you (or a
missile) away from the intended destination or target. This would be
fairly obvious on a yacht at sea.

In other words, don't worry about it. The 90% of the time you are on
your boat sitting at anchor it won't matter. The rest of the time
nobody cares to jam you.


i never said i was worried about it. i never said i thought anyone was
going to jam me. i never said i was going to high latitudes where i
thought geomagnetic storms would affect me. all i did was answer my
own question which was "can GPS fail ?". to my surprise, yeah, there
were some cases where it has failed. end of story.

GPS is a great tool, my primary navigation tool and i would assume the
primary navigation tool of anyone on a boat. i can't imagine any
reasonable situation where it would ever fail for me. but that doesn't
make understanding when it can fail some kind of crime, it doesn't make
me into some kind of anti-GPS zealot.


Don't forget that tinfoil in your ball cap.


i don't understand why you are being rude to me, i've not done anything
to you.

The ball cap comment was a joke aimed at Da Kine who seems lack a sense
of humour as well.

My comments on jamming are not intended to be rude.

You are being a bit sensitive.

Sorry.

Da Kine wrote:
As I understand it, they actually run off of a gyro system that is
better then GPS. Also, I have a good friend that captains a navy sub
that told me celestial navigation was required.

In your reading, pick up a red/orange colored paperback called
“Emergency Navigation�. Its available all over and you should be
able to find it at http://www.amazon.com for cheap. You won’t find
much of the good stuff in most books.

As for something else making GPS not work, there are a few things I
have come across and here they are.

On 9/11 GPS was scrabbled in many areas. For anyone in a critical
position in one of the scrabbled areas, OOPS!

In Mexico (and I love this one) I ran across and “electrical
engineer� that had a broken GPS and his spare didn’t work either.
This was a while back but … Turned out to be a bad antenna that I
fixed for him – the engineer☺

That’s the only way gps failures other then lighting that I know of.

As for a spare GPS, the rumor is that if you wrap a handheld in tinfoil
and get hit by lightning, your spare will still work. I don’t know
anyone that has put it to the test but I keep my spare wrapped just the
same.

GPS signals use to be scrabbled all the time. In about 1991 or so the
military started allowing public access of the gps signal. In times of
heightened defense alerts, the gps signal does get less accurate but
then there is also a differential signal that I don’t know much about
but is used to help the gps become more accurate again. All in all,
I’m more worried about lightning, having been through enough of it,
then anything else.

It's scrambled not scrabbled and they never were. The error was called
selective availablity. It made the more accurate signal only available
to military users. It has long since been discontinued because the
commercial sector came up with ways to make GPS very accurate without
SA. (Differential, WAAS etc)

As far as wrapping a GPS up in tinfoil. That is a good idea. It is
also helpfull to line your ball cap with tinfoil so aliens can't see
what you are thinking.

On 5 Mar 2006 14:20:24 -0800, "purple_stars"
wrote:

waynes i'm guessing that you mean that the navy doesn't teach RDF, not
that they don't teach celestial. only reason i say that is because it
seems like the military would need backups like celestial because i
understood that the EMP from a nuclear weapons blast could take out
electronics such as GPS systems. is that wrong ?

Yes, it's wrong. They no longer teach celestial. The military buys
EMP hardened electronics, and has for a long time.

Wayne.B wrote:
On 5 Mar 2006 14:20:24 -0800, "purple_stars"
wrote:


waynes i'm guessing that you mean that the navy doesn't teach RDF, not
that they don't teach celestial. only reason i say that is because it
seems like the military would need backups like celestial because i
understood that the EMP from a nuclear weapons blast could take out
electronics such as GPS systems. is that wrong ?


Yes, it's wrong. They no longer teach celestial.


You keep saying that. However, celestial navigation is shown as part
of the navigation course at the Naval Academy, which is required for
many majors.

The report from a few years ago which created your myth was that
celestial was no longer required for *all* majors.