Call yourself a navigator?'

[zoidberg]

There's a vigorous discussion within Facebook about this, between those who 'talk the talk' and those who can 'walk the walk'....
c/f The Practical Celestial Navigation Group.

FWIW, it's long been known that just about 'everyone and his uncle' had the capacity to jam or spoof GPS signals in an area of interest. That's been experienced time and again around UK maritime training areas, for presumed 'training and testing' of UK and NATO Services capabilities.

The Iranians are actively jamming GPS signals at present around the Straits of Hormuz and Eastern Persian Gulf.
.....iran-regime-is-jamming-gps-signals-in-strait-of-hormuz-to-disrupt-commercial-shipping.....

 

[capnsensible]

Always have a back up to your back up. Was drummed into my head!

So we have two sextants and for serious off shore can print some stuff off the internet before sailing to back up the tables.

Plus, of course, my wife can do astro.

Win, win.

 

[Kukri]

The RN Officers are both using Plath sextants!

You can still buy “surplus” RN grey sextants.

Plath have been out of business for a couple of decades.

Wassup?

(Yes, I have two Plath sextants, one that I’ve had for decades and an alloy frame one that I picked up cheap as a spare, ex German Navy, without a telescope, and which I now prefer. (The Plath 6x 30 is the East German Zeiss army monocular, if you find yourself without one...)The weak point of the Plath is the absolutely rubbish switch in the handle...)

 

[zoidberg]

I recently sold a perfect 'virgin' Freiberger Trommel sextant which had never been afloat.... at less than half list. I do have another SunGun which will see me out, but must replenish my working stock of pre-sharpened 2B IKEA pencils. My WorkMate Carpenters' Pencils aren't quite as good.....

 

[Skylark]

This thread has had me reaching for the Yellow Page within the Almanac. Slightly surprised to see that Dip/Ht of Eye correction is listed to 48m. That’s quite a bit more than the deck of my boat!

How high are the navigators in the video clip?

Would a junior rating have to send a weighted line overboard to measure heigh of eye

 

[GHA]

Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?

 

[Kukri]

Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?

I seem to have three GPS receivers with aerials in the panel at the back of the chart table, alone, so no... but the point being made is surely about spoofing of GPS signals?

 

[Wansworth]

The naval characters I have seen in films read their position directly off the sextant.....

 

[Kukri]

The naval characters I have seen in films read their position directly off the sextant.....

No; they have just memorised the tables and the Almanac and are good at mental arithmetic...

 

[vyv_cox]

Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?

Not on ocean crossing but in the Bay of Naples. Plotter lost signal, then tablet also. Within a few miles both came back. I was advised to contact a man who was investigating these black holes and was told this was a well known one. Military probably.

 

[laika]

There's a vigorous discussion within Facebook about this, between those who 'talk the talk' and those who can 'walk the walk'....

They just seemed to be doing noon sights in that video. Do they still teach lunars? If not they'll be stuffed if someone jams their chronometers

 

[lw395]

The point being made is about spoofing of GPS signals.

I imagine larger commercial ships don't put all their eggs in the GPS basket any more than the military do?
Presumably there are enough other nav aids in the gulf that losing GPS is an inconvenience rather than a real problem?

 

[GHA]

Not on ocean crossing but in the Bay of Naples. Plotter lost signal, then tablet also. Within a few miles both came back. I was advised to contact a man who was investigating these black holes and was told this was a well known one. Military probably.

Enough time to get the sextant out?

 

[Kukri]

I imagine larger commercial ships don't put all their eggs in the GPS basket any more than the military do?
Presumably there are enough other nav aids in the gulf that losing GPS is an inconvenience rather than a real problem?

It’s still a requirement for a British Certificate of Competence as an officer of the watch.

Yes, plenty of navaids in the AG. Which reminds me that MENAS, the Middle East Navigation Service, which maintains them and is so to speak the local Lighthouse Authority, is still somewhat “British”...

https://www.menas.org/

 

[GHA]

I seem to have three GPS receivers with aerials in the panel at the back of the chart table, alone, so no... but the point being made is surely about spoofing of GPS signals?

Question is still interesting though, has it actually happened to anyone here - long enough to require a sextant or be lost?

Do have a rather nice freiberger onboard which has never been needed in anger.

 

[JumbleDuck]

Plath have been out of business for a couple of decades.

http://www.weems-plath.com/Products/Sextants-Scopes-1/

 

[Sybarite]

Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?

No but in the time of Decca I lost all signals navigating up the E Coast of Ireland in thick fog. I had to resort to navigating by depth.

 

[AntarcticPilot]

I imagine larger commercial ships don't put all their eggs in the GPS basket any more than the military do?
Presumably there are enough other nav aids in the gulf that losing GPS is an inconvenience rather than a real problem?

The daughter of a friend of my wife is in training as a merchant officer. She has to do ALL the non-electronic navigation techniques. In fact, during her shore training she even produced a very nice hand-drawn imaginary chart with a large selection of symbols - as a former member of a map-making organization I was very impresssed with her work!

Forgot to say, she's training under the Hong Kong flag!

 

[Kukri]

http://www.weems-plath.com/Products/Sextants-Scopes-1/

I meant C. Plath, Hamburg, who made sextants. Weems and Plath are an American chart agent who sell Tamaya sextants.

C. Plath were bought and closed down by an American avionics company - something to do with having to have a German company to supply something to the German Air Force.

 

[zoidberg]

reaching for the Yellow Page within the Almanac. Slightly surprised to see that Dip/Ht of Eye correction is listed to 48m.

Ah, that'll be the Nautical Almanac, I reckon, or something similar. I 'cut my teeth' on the Air Almanac, which lists ( if memory serves ) a table for considerably higher Elevations of Height of Eye, initially for benefit of RAF Maritime Reconnaissance ( Shackleton/Sunderland ) navigators, and subsequent Nimrod navs. All RAF navs were trained, if not frequently practised, in Depressed Angle sights in respect of terrestrial and celestial objects.

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.

Anyone here actually lost all the gps's onboard and had to resort to astro on an ocean passage?

I suspect many of us have lost electrical power/batteries on rare occasion, AND also lost GPS signal on no-longer rare occasions. And many of us don't have any clear idea how to work ANY form of Reversionary Nav....

That's just 'winging it' IMHO, and is a wholly inadequate excuse for calling out the RNLI.