Call yourself a navigator?'

zoidberg said:
I recall one John Goode, a sea school Principal of the 'old school', describing how he clambered down low into a dinghy while on passage up the Red Sea, to give himself a much closer, more accurate, horizon as the low-lying normal one at around 7-8 miles was obscured in dust and haze.
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That’s in Lecky’s Wrinkles. I made a friend of a ferocious Scots Fleet Manager by saying I’d once done it. Better using the accommodation ladder as the dinghy bounces about.
 
GHA said:
Enough time to get the sextant out? ;)
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Here's a rhetorical question for you.....

Have you any idea how to use a sextant - and usefully plot the result - to give you a Horizontal Sextant Angle, a Vertical Sextant Angle, a Distance Off..... It's my understanding all Merchant Navy Cadets had to use the 'works sextant' to navigate in the Coastal Trade - headland to headland - doing just that, with the added benefit of a Dumb Compass for relative bearings.

Antarctic Pilot's contact should be able to confirm, as no doubt can Minn, that these basic, fundamental skills had to be mastered ( mistressed? :rolleyes: ) before beginning to peek at Heavenly Bodies.

It's not difficult. Anyone who can rub two brain cells together should be able to do it - provided, that is, they can 'be bovvered'.....


( And you have me pondering your use of 'GHA' as a monniker. To me, that 3-letter algorithm translates as 'Greenwich Hour Angle'. Do I scent a trollery? ;) )
 
zoidberg said:
Here's a rhetorical question for you.....

Have you any idea how to use a sextant - and usefully plot the result - to give you a Horizontal Sextant Angle, a Vertical Sextant Angle, a Distance Off..... It's my understanding all Merchant Navy Cadets had to use the 'works sextant' to navigate in the Coastal Trade - headland to headland - doing just that, with the added benefit of a Dumb Compass for relative bearings.

Antarctic Pilot's contact should be able to confirm, as no doubt can Minn, that these basic, fundamental skills had to be mastered ( mistressed? :rolleyes: ) before beginning to peek at Heavenly Bodies.

It's not difficult. Anyone who can rub two brain cells together should be able to do it - provided, that is, they can 'be bovvered'.....


( And you have me pondering your use of 'GHA' as a monniker. To me, that 3-letter algorithm translates as 'Greenwich Hour Angle'. Do I scent a trollery? ;) )
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I can certainly do all the coastal navigation uses of a sextant; they are all pretty easy and in pre-GPS days were a very useful addition to the toolbox, being capable of greater precision than compass bearings. My favourite was distance off - after all, that's why charts carry the height of marks! I know the theory of celestial navigation, but have never had to use it in practice. However, my knowledge of spherical trigonometry is certainly adequate for the job, and the use of the sextant for coastal navigation means that I can handle a sextant.
 
zoidberg said:
Here's a rhetorical question for you.....

Have you any idea how to use a sextant - and usefully plot the result - to give you a Horizontal Sextant Angle, a Vertical Sextant Angle, a Distance Off..... It's my understanding all Merchant Navy Cadets had to use the 'works sextant' to navigate in the Coastal Trade - headland to headland - doing just that, with the added benefit of a Dumb Compass for relative bearings.
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Vague idea but for fun could probably work it out pretty quick. For coastal nav if it goes awry the hand bearing compass is a much better bet imho.

Back to the OP, if losing GPS position is a real worry then, for the majority on here, forget dashing out to buy a sextant, get out and practice some blind nav pretending it's not just the gps that's gone, but the sun is behind the fog as well. Just how good can you get an EP? Then the fog lifts, how close can you get plotting a position with and hand bearing compass? Will be much more useful than a sextant fix with who knows how many miles accuracy.

Sextants are lovely though. :cool:
 
Peering at that YouTube vid ( above ) showing Cdr Stephens on the nav wing bridge of HM Queen Elizabeth, I recognised the Pelorus...


48494958476_3829ca3e9f_z.jpg



....as I have one exactly like that. Even the same paint-job. Well, minus the pedestal and gimbals, but mounted on a ply board for clamping onto my coachroof. Geek!

Well, how else is one to check compass deviation on a daily basis.....? Double-geek!
 
A good friend of mine had a total loss of ability to charge his batteries mid atlantic. Starter motor on engine died. Navigated to Horta on astro....he is good at it. An unusual problem right enough.

The loss of GPS signal may be more of a problem in the future though........who knows. But some Navies are now ensuring that they dont get lost.

Not had much use for a handbearing compass or blind nav out on the blue floppy stuff though!
 
Yes: Fixed GPS plus a "waterproof" Garmin 45 portable succumbed to excess salt water sloshing about below. By the time I'd washed it and dried it out in pieces in the oven it worked again and confirmed I could still do astro.

Have had all normally working GPSs fail to get signal though on several different occasions in the same area of the China Sea. Almost certainly PLA Navy jamming.
 
capnsensible said:
A good friend of mine had a total loss of ability to charge his batteries mid atlantic. Starter motor on engine died. Navigated to Horta on astro....he is good at it. An unusual problem right enough.
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Must be unusual these days with so many mobiles/tablets onboard - a few minutes turned on to get a fix once a day would get you a long way.

Would be fun to do a long one just with astro though, but ais is too useful solo & running the radar 24/7 eats too much juice.

Maybe not the greatest idea to cross oceans with just one source of charging....?
 
GHA said:
Must be unusual these days with so many mobiles/tablets onboard - a few minutes turned on to get a fix once a day would get you a long way.

Would be fun to do a long one just with astro though, but ais is too useful solo & running the radar 24/7 eats too much juice.

Maybe not the greatest idea to cross oceans with just one source of charging....?
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We are talking mebbe 8 or 9 years ago. Evrything finally ran out of amps. No lights, no radio, no nothin.

He subsequently fitted solar panels..... :)

I took the yacht across a couple of times. It was always, um, interesting. On one of the trips I switched gps off for around ten days. Everyone interested had lots of practice. I put it back on at supper time when EP suggested landfall in Antigua the next day. Was only 7 miles out. Quite impressed.
 
capnsensible said:
I took the yacht across a couple of times. It was always, um, interesting. On one of the trips I switched gps off for around ten days. Everyone interested had lots of practice. I put it back on at supper time when EP suggested landfall in Antigua the next day. Was only 7 miles out. Quite impressed.
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Good fun!

Regarding starter motors etc, towed a boat into Brazil once after his started burned out half way across when the start switch jammed on unnoticed. Plus in another port in Brazil must have been maybe a third ( quite a few anyway) of the boats coming up from South Africa came in with no engine. Losing an engine crossing oceans ain't rare :)
 
GHA said:
Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?
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Back in the day (1990) on passage from Gibraltar to Falmouth (ok, so not exactly ocean) the satnav didn't lose signal so to speak, but the position given led us to question the accuracy. Using the sextant we were able to establish that the digital read out was indeed wrong and the rest of the passage was competed using astro.
 
GHA said:
Must be unusual these days with so many mobiles/tablets onboard - a few minutes turned on to get a fix once a day would get you a long way.
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I don't think losing all GPS receivers is a serious concern nowadays (luddites with a single GPS128 and a clockwork telephone excepted), but failure (deliberate or accidental) of the incoming signals is a plausible risk.

Obviously warships in particular need to assume GNSS denial as a matter of course in modern warfare.

Pete
 
GHA said:
Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?
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number of GPS receivers doesn’t matter if there is jamming in your area. Russia jammed GPS signals in northern Norway during the NATO exercise last winter. Rescue services and commercial air transport was affected. The jamming transmitters have some reach but hopefully not mid Atlantic.
 
knuterikt said:
number of GPS receivers doesn’t matter if there is jamming in your area. Russia jammed GPS signals in northern Norway during the NATO exercise last winter. Rescue services and commercial air transport was affected. The jamming transmitters have some reach but hopefully not mid Atlantic.
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Commercial air traffic can function without GPS, but it tends to push them back to relying on a single system.
Mid Atlantic is not the problem, the problem starts when you start thinking you've reached the edge...
Before GPS, I know of someone who ended up cruising up and down the Nova Scotia fog banks trying to identify FM radio stations...
 
knuterikt said:
number of GPS receivers doesn’t matter if there is jamming in your area. Russia jammed GPS signals in northern Norway during the NATO exercise last winter. Rescue services and commercial air transport was affected. The jamming transmitters have some reach but hopefully not mid Atlantic.
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Same question though, has anyone lost all the GPS's onboard either due to jamming the signal or otherwise?

Would be interesting to see how big a problem it actually is - guessing next to none for the vast majority of us...
 
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