Clarification about the term "GPS Shutdown"

[Mxsmanic]

Nope. No clocks needed. Sheesh!

How do you know when it's noon without a clock?

The only way I can think of is to plot the movement of the sun over an
entire day. You can then see true north plotted directly. But an
entire day is a long time to wait. And if you are moving, that won't
help.

By being not utterly clueless, and having a vague idea about
constellations. Or by simply staring at space for about 1 minute,
by which time you'll be able to sense the circumpolar motion.
Go ahead, try it.

What if it's daytime?

By luck. People who navigate by straight lines generally fall off a cliff,
into a bog, down a mineshaft or wander into a firing range/ minefield /
alligator farm.

Not if they keep their eyes open.

And that got them from....

GPS receivers?

 

[Mxsmanic]

Tomorrow I could do it in 5 hours using only a stick.

Five hours is an extremely long time.

With a reasonably accurate dial watch, I could do it in one second. Thats a
£1 watch from a junk shop, not a chronometer.

Years from now, people will be saying exactly the same thing, except
that it will be a £1 GPS receiver from a junk shop, instead of a watch.

So, without a map, which way?

You need destination coordinates, and your coordinates.

Ah, so you need a map after all - or is there some other way to know the
coords of Khartoum?

You can ask someone who lives there.

I don't believe you.

So? It was part of what proved the value of GPS to me.

 

[Mxsmanic]

Time to wake up Bubba. He ain't never seen no big wreck before.

I'm just using the same reasoning being used to argue against GPS.

What if GPS fails?

Well, what if VOR fails? Or ADF? Or the magnetic compass?

The fact is, they are all more or less equally vulnerable, but human
nature is such that people will tend to reject what's new, rather than
what's old. They believe that anything new is less reliable, whether
this is actually the case or not.

 

[Mxsmanic]

He didn't need to. What did you think started the diesel up?

A human being, or a signal from a computer.

 

[Mxsmanic]

But it can be a component of one.

Components aren't good enough.

 

[Tom]

To maintain RNP 10 tracks over the oceans, an INS needs an

update every six hours.
Currently, the only way to do that is with GPS.

THAT IS NOT THE ONLY WAY. RPN 10 approval requires an airline to demonstrate
it's equipment meets certian accuracy requirements. Meeting those requirements
allows 6.2 hours of flight without position updates. Several means of updating
or increasing INS/IRS accuracy are mentioned, GPS is one but not the ONLY one.
See: http://www.faa.gov/ats/ato/rnp.htm
Quote from FAA order 8400.12A --- .
Effect of En route Updates. Operators may extend their RNP-10 navigation
capability time by updating. Approvals for various updating procedures are
based upon the baseline for which they have been approved minus the time
factors shown below:

(1) Automatic updating using DME/DME = Baseline minus 0.3 hours (e.g., an
aircraft that has been approved for 6.2 hours can gain 5.9 hours following an
automatic DME/DME update).

(2) Automatic updating using DME/VOR = Baseline minus 0.5 hours.

(3) Manual updating using a method similar to that contained in Appendix 7 or
approved by AFS-400 = Baseline minus one hour.

GPS is listed as a SUPPLEMENTAL navigation system by the FAA - aircraft can
still navigate without it. Maybe someday GPS will be required on aircraft, but
not now.

 

[Tom]

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

HAVE ILS.

Is that so? I would think that every airport in the world that passenger
airlines land at would have an ILS (instrument landing system = localizer and
glideslope). WOW. Don't ever fly on a rainny day! Maybe you'rer referring to
county airports and dirt airstrips?

 

[Juergen Nieveler]

You're at the top of Ben Nevis. Your destination is due north. Feel
free to walk north.

You're right tho, you won't need the rescue crew. And watch the first
step, its a big one.

Anybody got a back issue of that british newspaper? ;-)


Juergen Nieveler

 

[Juergen Nieveler]

Aviation experience shows that backup systems often don't help.

Which is why they have more than one backup...

What happens when radar breaks down? What are the backups?

For the ATC, another radar. Or if everything breaks down, they might
call the Pentagon and ask them to launch an AWACS bird if they're
really desperate.

Drawing upon the infinite quantity of fuel in your tanks.

If you were going in the right direction before the outage, why should
you suddenly be flying circles?

It shouldn't, if it's primary navigation.

GPS isn't primary navigation yet, though.


Juergen Nieveler

 

[Juergen Nieveler]

I just hate it when it's cloudy and I'm trying to orient myself with
the Sun, Moon or stars.... will on clowdy night, light pollution from
cities works pretty well.

During a day it's not all that bad - you can usually still see the sun
through the clouds.

And if you're lost in the woods on a cloudy night, that light polution
might prevent you from seeing the stars, but it tells you the direction
to the next city


Juergen Nieveler

 

[Juergen Nieveler]

How do you know when it's noon without a clock?

The only way I can think of is to plot the movement of the sun over an
entire day. You can then see true north plotted directly. But an
entire day is a long time to wait. And if you are moving, that won't
help.

Not nearly an entire day needed. Once it got to the highest position,
you'll note it going down again.

What if it's daytime?

You use all those other methods we keep telling you

Not if they keep their eyes open.

But you'd at the very least have to make huge detours - imagine a
terrain like grand canyon, with a map you can plan your route ahead.

GPS receivers?

Maps.


Juergen Nieveler

 

[Juergen Nieveler]

A human being, or a signal from a computer.

Turning a crank, after pre-heating the cylinders with a match? Hint:
Most diesel engines today are started electrically...


Juergen Nieveler

 

[Juergen Nieveler]

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).

There are churches with the choir and altar in the west? Got to be
pretty rare, at least in catholic areas.


Juergen Nieveler

 

[Juergen Nieveler]

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

Join the boyscouts. You findout where north is, orient your map, look
at the area around you for noticeable features (and on a 1:25000 map,
that includes trees), and fix your initial position. Easy. BTDT.

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

If your batteries run out, you're out of luck.

Juergen Nieveler

 

[Juergen Nieveler]

That was very recent.

Just how did the pilgrims manage to find the USA? And why didn't
anybody stop them?

Juergen Nieveler

 

[Juergen Nieveler]

How many churches are there between Medina and Mecca?

Look at the direction people are praying in, then.

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

If you don't even know THAT, you're screwed. Your GPS won't help you if
you suddenly find yourself on the wrong planet.

But you need a clock for that.

Not necessarily. You can measure height of the sun over the horizon -
highest position is noon.

How do you know which one is the polar star?

You don't even know THAT? Just how old are you, 8?

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

We could set you up on a normal field exercise, basic-training-style -
we'd send out a search team after a couple of days, don't worry.

Yes.

And if you get thrown out of a plane with just the order "Reach the
city of $FOO", you're still screwed.

From a Web site, usually.

You realise that you can't compare geocaching with real field trips,
let alone army exercises?

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.

Wrong. If you know your position and know where you want to go, you'll
end up next to that huge river and drown in a patch of quicksand -
which you would have known if you had a map.


Juergen Nieveler

 

[Mxsmanic]

Join the boyscouts.

I grew out of that long ago. I don't think I'd find the organization
interesting, especially if it is still depending on the moss on trees
for navigation.

 

[Mxsmanic]

Just how did the pilgrims manage to find the USA?

They sailed due west from a known point in Europe.

And why didn't anybody stop them?

Why would anyone want to?

 

[Mxsmanic]

Not nearly an entire day needed. Once it got to the highest position,
you'll note it going down again.

How? And what if you start at dawn?

But you'd at the very least have to make huge detours - imagine a
terrain like grand canyon, with a map you can plan your route ahead.

The detour is the same, though.

 

[Mxsmanic]

Look at the direction people are praying in, then.

In which direction do Christians pray?

If you don't even know THAT, you're screwed.

I guess the methods you suggest aren't valid for the tropics, then.

Not necessarily. You can measure height of the sun over the horizon -
highest position is noon.

Not if you are moving.

You don't even know THAT? Just how old are you, 8?

Which one is the polar star?

We could set you up on a normal field exercise, basic-training-style -
we'd send out a search team after a couple of days, don't worry.

Why would I want such blast to the distant past? Nobody navigates with
moss and stars today. Neither method is certified by the FAA, either.

And if you get thrown out of a plane with just the order "Reach the
city of $FOO", you're still screwed.

Why would that happen?

You realise that you can't compare geocaching with real field trips,
let alone army exercises?

Why are any of these being discussed? None of them is a terrorist
activity, and none of them is a frequent use of navigation among
civilians.

Wrong. If you know your position and know where you want to go, you'll
end up next to that huge river and drown in a patch of quicksand -
which you would have known if you had a map.

Maps are notoriously unreliable. Direct observation works better.