[QUOTE=BMCSRetired;100086] Who is John Harrison and why should we thank the almighty for him?[/QUOTE]
Read the book “Longitude”
[QUOTE=c.captain;100090]Read the book “Longitude”[/QUOTE]
If you lack the energy you could always watch the movie, which I have to say is pretty darn good, even if it is 4 hours long. Any decky who doesn’t know who John Harrison is should definitely look into that. Might put things into a new perspective for you. Definitely a valuable story to know.
What is more likely:
-
Thermonuclear war with upper atmospheric bursts to disable world-wide GPS and you would still be working for a shipping company who keeps sending your pay via direct deposit to cover the mortgage on your little plot of radioactive glass, or
-
Every one if your GPS devices sh*ts the bed (but none of the other electronics that control engine and power production) and celestial navigation saves the day!
The fact of the matter is that many deck officers rely very heavily on GPS/Electronic Chart systems. The well known weakness and possible failure point of this system is the signal from the satellites.
A common fix suggested is to train officers not to rely so heavily on the GPS/ECS but use the other methods available instead. The problem with this approach is it ain’t fucking going to happen. There is a whole generation of mariners out there that implicitly trust the GPS driven systems and trying to change mate’s habits by nagging has sharply diminishing returns. It’s not a matter of what watch officers “should” do on the bridge It’s a matter of what they actually end up doing. And what they end up doing is trusting the electronic systems
A realistic solution to this problem would be some kind of back-up such as LORAN or a inertia system which would reduce the reliance on GPS.
[QUOTE=Kennebec Captain;100069]Ha! If that happened he’d better have a clean engine room.[/QUOTE]
It took a while but I caught it, by golly. 
[QUOTE=Sweat-n-Grease;100052]That’s the spirit, Topsail.
Let’s make it competitive, you do one, I do one right after you and we compare. The best one gets treated to a cold beer. Either way we win, nobody watches someone with a cold one without grabbing one for himself…[/QUOTE]
I agree …
From your first observation from a DR position of 43°N / 047°W, you found an intercept of 2.5’ toward and an azimuth of 136°. But your calculations were based upon a chronometer 17 seconds fast instead of slow and unfortunately, you applied an index error of 2 minutes on the arc while it was off the arc.
- Find the correction to apply to your initial intercept due to your mistaken time on the chronometer,
- Find the correction to apply due the error in sextant altitude,
- Find the corrected intercept,
- Find your final observed position.
… 
[QUOTE=Topsail;100140]I agree …
From your first observation from a DR position of 43°N / 047°W, you found an intercept of 2.5’ toward and an azimuth of 136°. But your calculations were based upon a chronometer 17 seconds fast instead of slow and unfortunately, you applied an index error of 2 minutes on the arc while it was off the arc.
- Find the correction to apply to your initial intercept due to your mistaken time on the chronometer,
- Find the correction to apply due the error in sextant altitude,
- Find the corrected intercept,
- Find your final observed position.
… :D[/QUOTE]
There’s a reason it’s called Dead Reckoning.
I win.
I’m not fussy, any beer will do.
[QUOTE=BMCSRetired;100086]BTW, I taught myself and passed the tests. I didn’t need no stinking teacher.[/QUOTE]
Yes, we understand, BMCSRetired.
[QUOTE=BMCSRetired;100086]Who is John Harrison and why should we thank the almighty for him?[/QUOTE]
Yes, we understand, BMCSRetired.
[QUOTE=Sweat-n-Grease;100143]There’s a reason it’s called Dead Reckoning.
I win.
I’m not fussy, any beer will do.[/QUOTE]
And that’s why they offer this type of sextant …
[QUOTE=Kennebec Captain;100107]A realistic solution to this problem would be some kind of back-up such as LORAN or a inertia system which would reduce the reliance on GPS.[/QUOTE]
I flew in the Navy, way back in the 60’s. Inertial Nav was indeed used and it worked well. But, back then anyway, your “vessel” needed a bit more than 20 knots, although subs used them so perhaps I am, yet again, all wet. Obviously I am not up to speed. We need some input here, inertial nav is self contained and is immuned to external forces, or so I was told.
[QUOTE=Topsail;100145]And that’s why they offer this type of sextant …
[/QUOTE]
OK, you win.
Here’s an easy one for you Sweat-n-Grease … to merit your beer !
The sun rises with an angle with the horizon of 15°. What is your latitude 
Cripes, I read it as 46N and 114 W, good thing I didn’t send out my dogs. You would be Noah and most confused.
[QUOTE=Topsail;100154]Here’s an easy one for you Sweat-n-Grease … to merit your beer !
The sun rises with an angle with the horizon of 15°. What is your latitude
[/QUOTE]
I’m working on it, don’t hold your breath.
[QUOTE=Sweat-n-Grease;100156]I’m working on it, don’t hold your breath.[/QUOTE]
I’m giving you a cue … I’m turning blue !
At what angle is the sun rises with the horizon if you’re at the equator
[QUOTE=Topsail;100159]I’m giving you a cue … I’m turning blue !
At what angle is the sun rises with the horizon if you’re at the equator [/QUOTE]
Depends on what Cat House I found myself.
Don’t even need a sextant … :rolleyes:
I’m giving you a second cue … At what angle is the sun rises with the horizon if you’re frozen at the pole ?
The sun is rising parallel with the horizon if you find yourself back at the exact position, after sailing 50’ south, 50’ east and finally 50’ north !?!?
Exact or false …
Actually it’s called ded reckoning, as in deduced reckoning, but everyone misspells it nowadays.
North Pole, or anywhere on a latitude 57.97’ north of the South Pole.