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  1. #11
    Join Date
    Apr 2011
    Location
    Brighton
    Posts
    4,939

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by zoidberg View Post
    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 :-)

  2. #12
    Join Date
    May 2007
    Posts
    37,288

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by Minn View Post
    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?

  3. #13
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,394

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by vyv_cox View Post
    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?

  4. #14
    Join Date
    Jul 2008
    Location
    East coast UK. Mostly. Sometimes the Philippines
    Posts
    9,381

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by lw395 View Post
    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/

  5. #15
    Join Date
    Jun 2013
    Location
    Hopefully somewhere warm
    Posts
    9,394

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by Minn View Post
    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.

  6. #16
    Join Date
    Aug 2013
    Location
    SW Scotland
    Posts
    19,398

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by Minn View Post
    Plath have been out of business for a couple of decades.
    http://www.weems-plath.com/Products/Sextants-Scopes-1/
    "Seamen are always wanting to do things the proper way; and I like to do them my way."

  7. #17
    Join Date
    Dec 2002
    Location
    France
    Posts
    25,183

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by GHA View Post
    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.

  8. #18
    Join Date
    May 2007
    Location
    Cambridge, UK
    Posts
    6,042

    Default Re: Call yourself a navigator?'

    Quote Originally Posted by lw395 View Post
    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!

  9. #19
    Join Date
    Jul 2008
    Location
    East coast UK. Mostly. Sometimes the Philippines
    Posts
    9,381

    Default Re: Call yourself a navigator?'

    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.

  10. #20
    Join Date
    Nov 2016
    Posts
    2,460

    Default Re: Call yourself a navigator?'

    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.


    Quote Originally Posted by GHA View Post
    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.

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