if GPS were not available

[prv]

Would there be any significant advantages of a Yeoman plotter if there were no GPS available? I appreciate that bearings, and lat & long of waypoints etc., could be slightly quicker to obtain than by using a pencil and Breton plotter or ruler. But the principal advantage of the Yeoman, i.e. instant identification of current position, disappears if GPS fails.

I agree that pointing to your current position is the best feature, but the Yeoman was actually introduced before GPS so someone thought it was worthwhile without it.

It does have a little-used dead-reckoning mode - you click where you are whenever you get a visual fix, and in between it will DR based on either manually entered course and speed, or info from a log and compass via NMEA if available. The latter option ought to be more accurate than trad nav since it presumably integrates the data at some sampling frequency instead of using your estimate of an average for the whole period.

You can also put in a value for tide (obviously without GPS this is going to be a paper prediction, so no better than trad nav) and the positions it gives will thus be EPs.

Press the right-arrow key from the Nav mode to try it out.

Pete

 

[jimi]

EPIRB. Whenever I get lost (often) I just fire up the EPIRB and some chaps in an orange boat come and point me in the right direction.

Cheers, Brian.

What happens if your matches get wet? How do you light it then?

 

[Rum_Pirate]

What would your next best indispensible aid to navigation be?

Compass.

 

[Babylon]

If offshore, then a LW radio, watch, graph paper, and sunrise & sunset data. Used together, will give an approx Lat and Long. A sextant would be a bonus.

I'm really interested in this. Could you explain how its done?

 

[Tom Price]

[QUOTE=dylanwinter: "I can't see that GPS is ever going to stop".

BUT you might not be able to receive it! Which I found when last returning from Normandy. Whether it was too much fridge, electric loo, shower, ice-maker or anchor windlass I know not, but coming back down the Seine first the stereo died, then gps and chartplotter too as the domestic battery gave up the ghost.
Fortunately the ship's compass had been swung (it still doesn't enjoy beer cans nearby) so it was back to the chart, tidal atlas, parallel rules and mental gymnastics.

Fortunately echosounder and log still functioned, but I do carry a hand lead and vintage trailing log 'just in case'.
A selection of courtesy flags from Holland to Spain might be prudent, tho I usually ring SWMBO and ask her to look out of the window and wave . . .

 

[MoodySabre]

Doesn't the Yeoman use GPS?

Doesn't work without one

 

[snooks]

Compass.

But what use is a compass if you don't know where you are or where to go?

Or are we taking it for granted that charts are on board

 

[jimi]

Maybe its a pirate compass? Just like Johnny Depp's?

 

[FullCircle]

But what use is a compass if you don't know where you are or where to go?

Or are we taking it for granted that charts are on board

Snooks, you can always make a compass work the way you want ot to. I found that by keeping the Sea Searcher magnet in my jacket pocket, I could head in whatever direction I feel like, just by walking round the cockpit.

 

[Scotty_Tradewind]

If coastal, a compass and the Mk.1 eyeball.

If offshore, then a LW radio, watch, graph paper, and sunrise & sunset data. Used together, will give an approx Lat and Long. A sextant would be a bonus.

amongst all the things mentioned and missed off by most, I reckon a reasonably accurate timepiece would be high on my list.

 

[prv]

Doesn't the Yeoman use GPS?

Doesn't work without one

Does too. I've just been playing with mine in my very definitely non-GPS-equipped garden shed.

Granted, NA (nav) mode is a bit useless, but YE (yeoman), DR (dead reckoning navigation) and WAYPOINT all work fine. Although I wouldn't buy a Yeoman that could only do these, they are still useful.

Pete

 

[Signed Out]

But what use is a compass if you don't know where you are or where to go?

Or are we taking it for granted that charts are on board

I think we can make assumptions that many of us know that there's a big, cold place, via some hot ones, if you follow the S. Likewise a slightly smaller, but no less cold place, via some chilly ones if you follow the N.

Follow the E and there's some tall folk with good (well, strong) beer (but duff cheese), and follow the W for lots of water before not so good beer and very duff cheese.

Apparently. But then I spose you could just follow the sun.

 

[electrosys]

I'm really interested in this. Could you explain how its done?

A LW radio will give you the Greenwich Time Signal, and the watch is used to store GMT, giving you the 'zero' Long reference. The next thing you need is Local Noon.
This can be found by plotting the sun's altitude against time on graph paper as it crosses the sky. Begin (say) an hour, or half an hour before 'top dead centre' so to speak. With a sextant this can be done quite accurately, but a guessing stick can be used - anything by which to estimate the altitude. Keep plotting as the sun 'hangs' for a while and then begins to descend. All you really need is the time when a given rising and decending altitude is equal (i.e. the same angle), but plotting on graph paper enables you to better estimate, should you lose the sun behind a cloud at a critical moment. Then simply bisect the graph to give Local Noon. Greenwich Noon plus/minus Local Noon gives your Longitude.

Latitude can be calculated by recording local sunrise and sunset times and calculating local day length, which is then compared with the day length of a known reference latitude - or even pulled straight from tables (if memory serves).

Obviously this ain't precision position fixing ...

That's about the best explanation I can muster 'off the cuff' - I've got a better (fuller) explanation with some worked examples somewhere ... in the archives ... will dig 'em out if there's any interest.

 

[Signed Out]

Or without

I forgot that even a compass is unnecessary-

http://www.creartisto.com/sansboussole/index_en.html

 

[JayBee]

Loran C - It's still running as far as I know...

http://www.gpsworld.com/gnss-system/augmentation-assistance/news/loran-c-towers-bite-dust-10374

 

[Babylon]

A LW radio will give you the Greenwich Time Signal, and the watch is used to store GMT, giving you the 'zero' Long reference. The next thing you need is Local Noon.
This can be found by plotting the sun's altitude against time on graph paper as it crosses the sky. Begin (say) an hour, or half an hour before 'top dead centre' so to speak. With a sextant this can be done quite accurately, but a guessing stick can be used - anything by which to estimate the altitude. Keep plotting as the sun 'hangs' for a while and then begins to descend. All you really need is the time when a given rising and decending altitude is equal (i.e. the same angle), but plotting on graph paper enables you to better estimate, should you lose the sun behind a cloud at a critical moment. Then simply bisect the graph to give Local Noon. Greenwich Noon plus/minus Local Noon gives your Longitude.

Latitude can be calculated by recording local sunrise and sunset times and calculating local day length, which is then compared with the day length of a known reference latitude - or even pulled straight from tables (if memory serves).

Obviously this ain't precision position fixing ...

That's about the best explanation I can muster 'off the cuff' - I've got a better (fuller) explanation with some worked examples somewhere ... in the archives ... will dig 'em out if there's any interest.

That's brilliant. Thank you so much.

 

[Porthandbuoy]

Decca and Loran. They can always turn the transmitters on again . . . couldn't they? I've been hanging on to these Loran overlay charts for years on the off-chance.

Only kiddin'

Charts
Compass
Echo sounder
Sextant
Handspan at arms length = 11 degrees and a bit.

I have been on a jack-up rig, firmly sitting on the sea bed, and apparently doing 13 knots across the Libyan desert. That was at the start of Gulf War I when the dyslexic USA dept. of Defense were messing with the GPS sats.

 

[Deleted member 36384]

A coconut and maybe a stick.

 

[snooks]

A LW radio will give you the Greenwich Time Signal, and the watch is used to store GMT, giving you the 'zero' Long reference. The next thing you need is Local Noon. blah dee blah

All very handy if you just want to sail from Plymouth to Falmouth on a cloudy day!

 

[Fantasie 19]

If coastal, a compass and the Mk.1 eyeball.

Blimey... 21 posts in before I found the answer I would have given...