Clarification about the term "GPS Shutdown"

[Juergen Nieveler]

They haven't. Accurate navigational methods are a recent development.

For values of recent meaning "two hundred years"?

Only if he already knows where he is.

You only need to know ROUGHLY where you are - with an accuracy of more
than a dozen miles. Unless you've been blindfolded and dropped from an
airplane, that should be doable for most people, with the exception of
young officers, as anybody who served in an Army will tell you

If you know what map sheet you're on, and it's not too foggy or pitch
black night, you'll be able to find terrain features recognizable on a
topographical map.

Juergen Nieveler

 

[Juergen Nieveler]

How is it done?

Finding North? Lots of ways - the old "analogue wristwatch aiming at
the sun method" is slowly dying out as young people don't know how to
read an analogue watch anymore, but there's lots of telltale signs that
you can use instead which are good enough to find north with a degree
of accuracy good enough to identify terrain features and triangulate
your position.

Methods are for example:
- Vegetation (In temperate zones, moss only grows on one side of a tree)
- Old buildings (Churches can be seen from far away, and the choir is
always in the east) - same for old graves, but don't get confused by
new graves on old graveyards
- New buildings (Satelite antennas for TV will point rougly South-
Southeast in the northern hemisphere)
- At noon, the sun will be in the south (adjust for DST...)
- At night, you can spot the polar star if you're in the northern
hemisphere

If you know where you are, that's half the trip.

Nope, not even close. You might know exactly WHERE you are to within a
few millimeters, but without a map that information is totally useless.
At the very least, you'll have to know the coordinates of the spot you
want to go to.

I've regularly used GPS without a map.

But you knew the coordinates of the spot you wanted to reach, didn't
you? Which you had from an external source, such as a map.

Knowing your position is nice, but if that's all you know then all you
can do is give this position to the rescue crews trying to find you.


Juergen Nieveler

 

[Juergen Nieveler]

There is no such thing. No diesel generators starts in under a
millisecond.

Never claimed that. Ever heard the term "UPS", apart from parcel
delivery?

Usually, such systems have a stack of batteries that will last for a
few minutes at maximum load - enough time to start the diesel and get
it running at normal RPMs.

No, companies get stuck with similar disclaimers.

Depends on what they are willing to pay. For example, at work we have
an MPLS connection that is backed up by another MPLS connection running
on hot-standby, routed through a different Telco and a different main
node in a different city - and if both fail at once, the ISP will get
it repaired within 4 hours, or he'll have to pay a huge amount of money
to us to make up for the downtime.

Describe one.

A loney putting chemical time-bombs in several US cities, set to
explode at the same time, synchronized by GPS, without any other
methods of synchronisation because the loney thinks that GPS would
never be shut down.

You'll claim that if companies have contingency plans, so will the
terrorist - but the difference is that companies shouldn't be run by
loneys...


Juergen Nieveler

 

[Iolaos]

It's a mystery then how people have managed to navigate with only map
and compass for ages...

Actually, they frequently got lost and starved to death or died
of scurvy.

It's pretty difficult to tell where you are in the ocean with
only a map and a compass.

And they didn't attempt thousands of ocean crossing every day at
500 miles per hour, either.

 

[Frank Looper]

True, a compass alone won't help - but a compass and a map in the hands

of somebody who knows how to use them are just as accurate as GPS.
Using map and compass is slower, but more reliable... a compass doesn't
need batteries.


Juergen Nieveler

A sextant and a reliable chronometer would be the rest of the package.

With those, if you're experienced at it, you can find where you are to the
level of a GPS during SA days.

Frank

 

[Alan Browne]

Possibly ... or hitting mountains.

What you know about aircraft navigation is even less than what you know about
GPS, which is clearly very little.

Just because they're older? Which of them is "most primary"?

Aircraft dependant. Basic VFR requires no more than a magnetic compass, T&B,
airspeed, altimeter and a clock. Basic IFR requires a little bit more.

A 'decently' equipped IFR single engine aircraft would have 1 ADF, 2 VOR's, 1 GS
receiver, MB RX and hopefully a DME. that would get you about very handilly for
CAT I approaches. (A transponder too of course, but that is not a nav system
for the pilot).

Most widebodies (and most recent narrow bodies) have everything above plus dual
or triple INS. These systems is integrated via nav management systems for
guidance. The pilot can select the nav guidance combinations of choice.

Gee, I haven't meantioned GPS. Don't have too. KLM's MD-11's for example are
still GPS free and cert. for at least CAT III. Most B-747-100/200's are not
equipped with GPS, and most likely will never be. There have been a few
integrations on -200's and 300's, which are effective, but expensive. I would
bet that most -400's built before 1994 do not have GPS.

B-777 was the first airliner built that had GPS designed in from the intitial
design stage ... but can of course navigate on its INS, VOR, DME, ADF systems
quite well including CAT III approach (ILS+INS) if the GPS is Tango-Uniform.

Cheers,
Alan.

 

[Alan Browne]

Juergen Nieveler writes:




Between cycles of line power so as to avoid any power outage to critical
equipment? Even with a major credit card, I don't think that would be
possible.

Look up uninterruptible power supply (UPS). Very common in large computer
centres and now available in quite small and affordable systems. They click on,
giving you more than enough time to start the generators. Many of them will
signal a generator to start automatically and manage the transition more than
smoothly enough to protect the power supplies of the equipment.

Not so for any utilities.

Tell that to the NE US.

 

[Alan Browne]

Most missiles take less than seven days to reach their targets.

So you would have to steal the keys after you are ready to launch. good luck.
you would aslo have to have another item to make it work.

That has never stopped spies from leaking them in the past.

Timing is everything. Lessons from the past apply as well.

It would have far more impact than destroying the World Trade Center.

I doubt it. Nobody that I know of died last summer.

And the terrorists will be doing all this, too.

Good that they be distracted and that their task made harder.

 

[Sam Wormley]

A sextant and a reliable chronometer would be the rest of the package.

With those, if you're experienced at it, you can find where you are to the
level of a GPS during SA days.

Frank

Wonder what the cost of asextant and a reliable chronometer compared
to a GPS receiver.

 

[Frank Looper]

Wonder what the cost of asextant and a reliable chronometer compared

to a GPS receiver.

Well, you're wearing a reliable chronometer (quartz ocillator timing), and a
sextant can be had for less than 50 USD.

Frank

 

[Iolaos]

Not a single one of which would catastrophically fail.

Or hitting each other.
There are LOTS of airplanes in the sky these days.

Because all those other navigation systems suddenly failed as well, and
ATC couldn't see the plane on their radar, and somehow the pilots
weren't able to look out of the window anymore? If an aircraft would be
in such a desperate situation, they'd declare inflight emergency and
get a military escort - problem solved, the military aircraft would
still be able to navigate.

There are hundreds of civilian aircraft for every military
aircraft.
Good luck.

Depends on which part of the flight. For transoceanic flights it would
be LORAN,

I haven't seen a LORAN in an airplane in decades. I'm not even
sure LORAN is available outside the USA.
Primary for oceanic flights is GPS.
It's the only thing that provides the precision required for
flights on the new narrower tracks for flights over six hours.
The backup (primary on older airplanes) is INS, but that drifts
too much to be used after six hours.

for final approach ILS...

The majority of the airports in the world (and in the USA) don't
HAVE ILS.

There's already talk of decomissioning the VOR/DME and possibly
the ILS system in favor of GPS.

 

[Sam Wormley]

Well, you're wearing a reliable chronometer (quartz ocillator timing), and a
sextant can be had for less than 50 USD.

Frank

400,000 per month to keep up with GPS receiver sales according to
"GPS World".

 

[High Sierra]

Well, you're wearing a reliable chronometer (quartz ocillator timing), and a
sextant can be had for less than 50 USD.

Frank

Heck, you could make a usable sextant for a few bucks. However it wouldn't be as
accurate, tho it will probably get the job done.

 

[Philip Homburg]

- Old buildings (Churches can be seen from far away, and the choir is
always in the east) - same for old graves, but don't get confused by
new graves on old graveyards

Except when the choir and the graves are west of the church. (I assume that
17th/18th century can called 'old'. Otherwise the 'can be seen' from far
away part becomes a bit tricky).

 

[Mxsmanic]

For values of recent meaning "two hundred years"?
Yes.

You only need to know ROUGHLY where you are - with an accuracy of more
than a dozen miles.

You won't be any more accurate in your navigation than you were in your
initial position.

If you know what map sheet you're on, and it's not too foggy or pitch
black night, you'll be able to find terrain features recognizable on a
topographical map.

If the wind blows away your map, you're out of luck.

 

[Mxsmanic]

Its quite incredible isn't it, that people managed to sail from Liverpool
to New York on a fortnightly basis ...

When?

 

[Mxsmanic]

Wonder what the cost of asextant and a reliable chronometer compared
to a GPS receiver.

GPS receivers are much cheaper.

 

[Mxsmanic]

Finding North? Lots of ways - the old "analogue wristwatch aiming at
the sun method" is slowly dying out as young people don't know how to
read an analogue watch anymore, but there's lots of telltale signs that
you can use instead which are good enough to find north with a degree
of accuracy good enough to identify terrain features and triangulate
your position.

The fact that the need for accurate navigation throughout the ages has
been a consistent motor of technological progress would seem to indicate
that simply looking for moss on the side of a tree just isn't good
enough for many practical applications, however useful it might be to
boy scouts.

Methods are for example:
- Vegetation (In temperate zones, moss only grows on one side of a tree)

I see moss on all sides of trees in my region, and it's a temperate
climate.

- Old buildings (Churches can be seen from far away, and the choir is
always in the east) -

How many churches are there between Medina and Mecca?

- New buildings (Satelite antennas for TV will point rougly South-
Southeast in the northern hemisphere)

But you have to know which hemisphere you're in.

- At noon, the sun will be in the south (adjust for DST...)

But you need a clock for that.

- At night, you can spot the polar star if you're in the northern
hemisphere

How do you know which one is the polar star?

Nope, not even close. You might know exactly WHERE you are to within a
few millimeters, but without a map that information is totally useless.
At the very least, you'll have to know the coordinates of the spot you
want to go to.

And that's practically all you need in many cases. I've proven this in
the field many times.

But you knew the coordinates of the spot you wanted to reach, didn't
you?
Yes.

Which you had from an external source, such as a map.

From a Web site, usually.

Knowing your position is nice, but if that's all you know then all you
can do is give this position to the rescue crews trying to find you.

If you know your position, you know which direction to move in order to
reach your destination. And then you don't need the rescue crews.

 

[Mxsmanic]

Here's a hint: there's this astonishing thing called "the sun".

The sun moves through the sky, and without a clock or a great deal of
patience, it'll take a really long time to find geographic north.

So. You know you're at 15.60N 32.53E.

Which allows you to decide which way to go to reach your destination.

Which direction do you go in, to get to Nairobi? Or Khartoum ? Or London?
No using a map (or substitute such as the web) to find out.

You just need coordinates.

Me too. But to navigate? I think not.

Yes, to navigate.

 

[Mxsmanic]

I doubt it. Nobody that I know of died last summer.

Nobody that I know of died at the World Trade Center, either.

Good that they be distracted and that their task made harder.

It doesn't matter once they execute the plan.