Can you navigate without using GNSS?

[Beelzebub]

I've still got my sextant

 

[Praxinoscope]

I've still got my sextant

so have I but it’s a bit OTT nowadays as I tend to only do coastal sailing now, just don’t want to let it go.

 

[Birdseye]

Easy question.

Me? Yes.

Yes - its simple vector maths for the most part

 

[zoidberg]

Can you navigate without using GNSS?

Of course. That's what HMQueen paid me for. But whether I need a 'carpenter's pencil' or a draftsman's Scheaffer 0.4mm 'sharpie' for my DR depends on the audience... and the examiner!

Back in the day, I had a couple of Decca Navigator 'pressies' of 5" Portland Protractors with neat cutouts for DR , MPP and Assumed Position.... worth a handful of points in the Assessed Nav parts of NATO Bombing Competitions. I still have 'em somewhere.... just in case.

Oh, the learned arguments about the validity of a sound 2-LOP fix versus adding the third ropy line, and the invocation - always at dead of night somewhere between Start Point and Alderney - of the Reduction of Uncertainty by means of ropy statistical Bands of Error.....
I once tried to explain this esoteric side-branch of Pro Navigation to one James Stevens. As I recall, his eyes glazed over and he fell into something akin to a hypnotic trance!

Oh, and there's a genuine-beduine laminated RAF Coastal Command 'CONSOL' Chart up in the loft, which I used to good effect on several of my early RORC races. Yes, contrary to scurilous rumour I could count up to 60....

Gee, this is better than any old anchor wrangle!

 

[dunedin]

The question now should be ….. can you navigate without GNSS/ GPS and without paper charts? As that is what UKHO - and MCA - seem to think will happen.

 

[Frogmogman]

Or Decca?

And why people called it Desmond?

Not only do I remember Decca, I remember the old school version with special decca charts and a big box of tricks with four “deccometers” whose coordinates you then plotted on aforementioned Decca charts. It worked fine until it rained…..

My first experience of Satellite navigation was on a 1981 transatlantic trip on an Ocean 71 called second life (the boat in which Gerry Dijkstra was dismasted in the Ostar in 71 or 72, and which Roddy Ainslie skippered in the first Whitbread). The unit on board was a Navidyne ESZ 4000 which would give you a fix every four hours or so, which TBF is fine for ocean navigation. IIRC, back in 1981 it had cost $12000.

oh, and shame on you for being disrespectful to Desmond Dekker, one of my all time favourite singers.

 

[Buck Turgidson]

Can you navigate without using GNSS?

Of course. That's what HMQueen paid me for. But whether I need a 'carpenter's pencil' or a draftsman's Scheaffer 0.4mm 'sharpie' for my DR depends on the audience... and the examiner!

Back in the day, I had a couple of Decca Navigator 'pressies' of 5" Portland Protractors with neat cutouts for DR , MPP and Assumed Position.... worth a handful of points in the Assessed Nav parts of NATO Bombing Competitions. I still have 'em somewhere.... just in case.

Oh, the learned arguments about the validity of a sound 2-LOP fix versus adding the third ropy line, and the invocation - always at dead of night somewhere between Start Point and Alderney - of the Reduction of Uncertainty by means of ropy statistical Bands of Error.....
I once tried to explain this esoteric side-branch of Pro Navigation to one James Stevens. As I recall, his eyes glazed over and he fell into something akin to a hypnotic trance!

Oh, and there's a genuine-beduine laminated RAF Coastal Command 'CONSOL' Chart up in the loft, which I used to good effect on several of my early RORC races. Yes, contrary to scurilous rumour I could count up to 60....

Gee, this is better than any old anchor wrangle!

My dear departed father would have raised an eyebrow at Gee! ;-)

 

[Kukri]

Yes.

And I can make my own paper chart, if I need one, having watched HW Tilman calmly make a chart of the Irish Sea because we hadn’t been expecting to go that way.

I last saw a twiddle the dials Decca Navigator in the wheelhouse of the frigate HMS Sheffield in 1996. That was seven years after I had thrown them off the ships of the Swire Group and told everyone to nip down to the yacht chandlers and buy a Walker, thereby saving us US$ 87,000 a year in paper lattice charts.

But the Grey Funnel Line got their Decca charts free. Big difference.

 

[zoidberg]

Yes.

And I can make my own paper chart, if I need one, having watched HW Tilman calmly make a chart of the Irish Sea because we hadn’t been expecting to go that way.

I last saw a twiddle the dials Decca Navigator in the wheelhouse of the frigate HMS Sheffield in 1996. That was seven years after I had thrown them off the ships of the Swire Group and told everyone to nip down to the yacht chandlers and buy a Walker, thereby saving us US$ 87,000 a year in paper lattice charts.

But the Grey Funnel Line got their Decca charts free. Big difference.

Aye, laddie. That'll be a Mercator Projection, I imagine. But would you manage wi' some other popular projections...?

( I'm betting there's less than 1 in 100 who come on here who even know there ARE other projections, never mind what to do with them.... )

 

[Kukri]

Aye, laddie. That'll be a Mercator Projection, I imagine. But would you manage wi' some other popular projections...?

( I'm betting there's less than 1 in 100 who come on here who even know there ARE other projections, never mind what to do with them.... )

Of course it would be Mercator, since I would be planning to navigate on it, using my own limited abilities, and I would not be planning to navigate anywhere where Mercator does not suffice.

 

[AntarcticPilot]

Aye, laddie. That'll be a Mercator Projection, I imagine. But would you manage wi' some other popular projections...?

( I'm betting there's less than 1 in 100 who come on here who even know there ARE other projections, never mind what to do with them.... )

Well, I do - and routinely used several. Mercator isn't a lot of good in the polar regions. I still have reference material on my bookshelves - I implemented computer software for quite a few! Polar Stereographic was the routine one for me, with Lambert Conformal Conic as another regular one, with Lambert Equal Area for some purposes. My least favourite is Mercator, normal or transverse, mainly because the ellipsoidal equations are intractable; you have to use Taylor Series, with inevitable loss of precision. A really fun one was Space Oblique Mercator, but thankfully that was only in vogue in the early days of the Landsat satellites; it was basically a mathematical description of the imaging mechanism of early remote sensing satellites.

I've been involved in ISO standards for coordinate systems, too.

I imagine that Tilman would have used Plat Carree; that's much the simplest to construct manually. Mercator is actually pretty difficult to do accurately.

 

[Kurrawong_Kid]

Hmmm, still have and use the Yeoman, big picture on paper and x marks the spot if all dies.
BUT when paper dies will have only old uncorrected charts ? ?

+1 with NASA GPS repeater in cockpit linked to the Yeoman. When route planned, if using out of date charts, I check the positions of buoys, shallow patches etc.on navionics on my phone and amend the charted positions on the outdated charts. Will continue to do this when paper charts are dispensed with! Yeoman is a great system, not in your face, not subject to screen invisibility in bright sunlight and route planning is on a decent sized surface, not peering into an ancient small TV like screen!

 

[zoidberg]

That's me told... which is all to the good!

I once had to construct a Mercator chart-of-sorts on the back of an old topo chart, while airborne. Someone had 'pirated' my navbag and removed the current EnRoute and Airways charts. There was/is a 'quick and dirty' method of expanding the Parallels by drawing in the angular mid-latitude(s) successively from a selected 'origin' Lat/Long, depending on track quadrant. Over modest distances, this proved sufficiently accurate for Air Traffic Reporting purposes.

No-one ever knew.... until now!

 

[Uricanejack]

Yep, usual routine

 

[Chiara’s slave]

+1 with NASA GPS repeater in cockpit linked to the Yeoman. When route planned, if using out of date charts, I check the positions of buoys, shallow patches etc.on navionics on my phone and amend the charted positions on the outdated charts. Will continue to do this when paper charts are dispensed with! Yeoman is a great system, not in your face, not subject to screen invisibility in bright sunlight and route planning is on a decent sized surface, not peering into an ancient small TV like screen!

Theres a plug in our saloon that belongs in the Yeoman, it is brought out whenever we are out of visual home territory. Just seems the right thing to do, keeping a paper record. We could fall back entirely to it if required, but I don’t do that for sh1ts snd giggles, 2 of us on board, the purpose of the plotter is to navigate from the cockpit.

 

[Wansworth]

I have my school atlas

 

[Kukri]

I have my school atlas

And a dollar alarm clock that you have boiled to make it run right.

 

[AntarcticPilot]

And a dollar alarm clock that you have boiled to make it run right.

But you need lunar tables and a sextant to make that work!

 

[Neeves]

Its all too complicated - no wonder it is called the lucky country

We just count the lighthouses as we head south from Sydney.

Jonathan

 

[Kukri]

Well, I do - and routinely used several. Mercator isn't a lot of good in the polar regions. I still have reference material on my bookshelves - I implemented computer software for quite a few! Polar Stereographic was the routine one for me, with Lambert Conformal Conic as another regular one, with Lambert Equal Area for some purposes. My least favourite is Mercator, normal or transverse, mainly because the ellipsoidal equations are intractable; you have to use Taylor Series, with inevitable loss of precision. A really fun one was Space Oblique Mercator, but thankfully that was only in vogue in the early days of the Landsat satellites; it was basically a mathematical description of the imaging mechanism of early remote sensing satellites.

I've been involved in ISO standards for coordinate systems, too.

I imagine that Tilman would have used Plat Carree; that's much the simplest to construct manually. Mercator is actually pretty difficult to do accurately.

Tilman used a far quicker and simpler method - one that works for any latitude for which you have a paper chart of a similar scale. He had the small scale chart of the North Sea as we had sailed up it.

Prick through the latitude and longitude lines, turn the chart over, and draw them using a pen and the parallel rulers. Name them for the longitudes that you want to sail through. Using the Light List, mark the lights and their characteristics. Result, in this case, a chart of the Irish Sea. Navigate to keep on the right side of the lights and a safe distance off.