I don't think an EMP would take out GPS

[Hitch]

I was curious about something. We've all heard the doomsday scenario where a nuke detonated above the US would create an EMP that would fry all the electronics. All the cars would stop, no power, no phones, lights out, etc...

Lot's of books written on this topic. I've read quite a few.

Best I could figure, that nuke would have to be maybe a few hundred kilometers above the country to cause that. GPS satellites are 20,000 kilometers high in orbit.

Seems logical to me that those satellites would be just fine and continue to orbit without any damage. So, a handheld GPS, if protected from the intitial EMP blast, should work just fine as well and provide your position.

[palani]

Seems logical to me that those satellites would be just fine

I don't have any particular intelligence on this but I would presume the U.S. would shut down fairly quickly any system that could be used for guidance for incoming missiles.

[Hitch]

I don't have any particular intelligence on this but I would presume the U.S. would shut down fairly quickly any system that could be used for guidance for incoming missiles.

Damnit palani. I bet you are 100% correct. So much for that idea. Oh well, I guess I will have to use a sextant to navigate.

[palani]

I guess I will have to use a sextant to navigate.

Noon sun sight, chronometer and taffrail log.

[Hitch]

Noon sun sight, chronometer and taffrail log.

dead reckoning. I think I'm here. Plot. I want to go there. Plot. Go compass! :)

[palani]

dead reckoning

DR is what you do between fixes. Sextant isn't really useful for dead reckoning. It is useful for fix.

[Hitch]

Sextant isn't really useful for dead reckoning. It is useful for fix.

You can't use a sextant with out dead reckoning. You need a DR point. You have to start somewhere, where you "think" or more so "hope" you are. Once you have a DR, then you can use the sextant to get fix.

[palani]

You can't use a sextant with out dead reckoning. You need a DR point.

Nope. HO214 ... use sight reduction of stars. Each star has a GP (geographic position) that it is directly over on earth. Chances are you aren't going to find one of these directly overhead but you might hope for one 2-3 degrees off your present GP. You find three of them and each sight reduction gives you a circle. You might be anywhere on that circle but with three circles there will be one point where they all intersect.

With only two stars you end up with two circles and then you have two points of intersection. DR might come in handy to choose which intersection you are at.

Either way you need an accurate chronometer and the table from HO214.... plus it helps to know your stars.... and a good horizon is a must.

[Hitch]

Nope. HO214 ... use sight reduction of stars. Each star has a GP (geographic position) that it is directly over on earth. Chances are you aren't going to find one of these directly overhead but you might hope for one 2-3 degrees off your present GP. You find three of them and each sight reduction gives you a circle. You might be anywhere on that circle but with three circles there will be one point where they all intersect.

With only two stars you end up with two circles and then you have two points of intersection. GP might come in handy to chose which intersection you are at.

Either way you need an accurate chronometer and the table from HO214.... plus it helps to know your stars.... and a good horizon is a must.

In theory, yes. In practicality, there's more to it. You are moving at the time, plus, add in the swell and/or pitch of the boat, getting it accurate is not that easy. This is where DR helps. If you have a starting point, you can take a minimum of 3 fixes, and you'll likely be somewhere in that triangle of fixes. A DR helps make that triangle smaller, basically like knowing which page in a book to look for first.

Good post.

[palani]

you can take a minimum of 3 fixes, and you'll likely be somewhere in that triangle of fixes.

In the spirit of friendly debate ... there is no such thing as a triangle of fixes. You either got a fix or you got a guess.

If you know how to recognize stars when you go outside you can tell which ones are the closest to overhead. These are the ones you look up in the table once you take a sight. You also have to take the time between sights into account because you aren't standing still. You use DR to move each sight reduction based upon the distance you traveled between sights. If you are fast this will not be much but otherwise could be termed a 'running fix'.

[Hitch]

In the spirit of friendly debate ... there is no such thing as a triangle of fixes. You either got a fix or you got a guess.

Well, I suppose if you put it that way....a triangle of fixes is three guesses. ;D You are somewhere in that triangle though. :)

[palani]

You are somewhere in that triangle though. :)
When these things don't work out reefs have a habit of becoming named.

[Hitch]

When these things don't work out reefs have a habit of becoming named.

Reefs get named after people who have the courage to discover them. You don't get a reef named after you if you live a life of 'theory'. :)

[palani]

Reefs get named after people who have the courage to discover them. You don't get a reef named after you if you live a life of 'theory'. :)

Not a life achievement award. Try putting your reef's name and location on your next resume and see if your future employer appreciates your courage or if he would rather applaud a successful voyage.

[Hitch]

Not a life achievement award. Try putting your reef's name and location on your next resume and see if your future employer appreciates your courage or if he would rather applaud a successful voyage.

Palani...if you discover a reef, it's UNCHARTED!!!!

It's pure bad luck. No amount of exception navigation skills you have can prevent that.

Keep sitting behind your desk, that's the safe bet.

[palani]

Palani...if you discover a reef, it's UNCHARTED!!!!

They can be uncharted or .... just plain bad navigation.

Case in point: Anegada is the first island you arrive at in the Caribbean from the med. It's 15 feet high at its' highest point. Miss it to the north and you have some of the deepest water in the Atlantic. Miss it to the south and you end up in a shallow area of coral reefs (called Horseshoe Reef) and there you will find hundreds of ships whose navigation was off by a mere 4-5 miles and didn't spot Anegada.

A guy I knew a 55 foot ketch from the med to Caribbean using only noon sights and a taffrail log.

[Hitch]

Miss it to the south and you end up in a shallow area of coral reefs (called Horseshoe Reef)

That reef is a named reef. I thought we were talking about unnamed reefs, ie unknown reefs, also called UNCHARTED reefs.

Take your pick and choose your argument. Which would you rather discuss? Mariners that crash into uncharted reefs, or mariners that crash into reefs that are named (known).

[gunDriller]

i'm not sure why people make a big deal about EMP.

yes, it is a way to monkey-wrench the US economy & most (non-EMP-hardened, technology dependent) western economies.

BUT it is not easy to do.


with Israel and a Judeo-Fascist crime gange basically running the US gov - i'd say we have bigger problems.


re EMP - one concern is Jews doing a false-flag, using EMP.

[Neuro]

i'm not sure why people make a big deal about EMP.

yes, it is a way to monkey-wrench the US economy & most (non-EMP-hardened, technology dependent) western economies.

BUT it is not easy to do.


with Israel and a Judeo-Fascist crime gange basically running the US gov - i'd say we have bigger problems.


re EMP - one concern is Jews doing a false-flag, using EMP.
I think it is silly to do an EMP as a false-flag. You do a false flag to get a response out of the victim, but with an EMP, you strike the victim out,