how accurate is your compass?

[nik]

With the compact nature of consoles on ribs, there tends to be a lot of ironwork and electronics surrounding a console mounted compass.

I checked mine the other day, and it was out by 45 degrees. That could be a bit of a problem if you had to rely on it.

The compass is a ritchie make, so I dont think its a rubbish compass, its just the clobber around it. It can be adjusted, but I havent tried yet.

So, how accurate is yours?

Nick.

[mdt]

really could not say as it is sat in the garage... as you say not a lot of space on the rib and wanted to fit a fishfinder.

[Biggles]

Checked mine on the high seas and its great.

Even though its next to tons of electronics including a VHF !

[Erin]

Stating the obvious perhaps..... but I assume you've got it positioned on the 'lubber' line and not set at some angle from fore/aft.

[nik]

hmm, Lubber line?

[nik]

lets put it this way. The compass is on the centre line of the boat. And if I look down the centre line, it is off by 45 degrees.

[Chris Murray]

If you have room, one of these would be perfect!

I used to have one on my previous boat, a (far less comfortable) sports cruiser. I would put one on the Scorpion but there is nowhere to fit it.

I understand that these were built to military specification and - based on the treatment it received on my last boat - I think this is probably correct.

I am slightly reluctant to put a locker-mounted sensor to link up with the chart plotter (as I can't fit an Azimuth) because there are nasty things like anchors down there!

Chris.

[Rogue Wave]

Originally Posted by Chris Murray

If you have room, one of these would be perfect!

Chris.

Yep that#s what we use out here but if the leccy fails then you need tohave another compass, I use a lanyard plastimo something. It#s yellow and it cost about 40 quid. always ready and not surounded by wires

[Tomas]

Proper care and feeding of a magnetic compass is a subject that lends itself to some study. How to apply magnetic compass readings to charts correcting for true vs. magnetic North, even with a properly installed compass with a properly achieved deviation table is a formula based on your location latitude and longitude wise and your particular installation and being in possession of proper nautical charts.

Navigation based on compass points has been reduced to an "ancient" art as most "modern" navigators, especially pleasure boaters, utilize chart plotting GPS units and don't know a thing about compass navigation, don't own the charts to make a compass of much use and don't intend to have parallels or dividers on board either. Great suggestion for a thread "Where do you stow your Sextant on your RIB"

I don't know about the Royal Navy but the U.S. Navy abandoned Sextant Navigation training at the Navel acadamy a couple of years ago and now teaches only "Electronic" Navigation.

Forget the compass, bust for a chart plotting GPS if you travel in places where you lose visual reference to landmass and have a nice day.

Tomas

[Apherel]

whatever we do in practice, the ability to work with compass and charts remains an essential skill.

The vast majority of RIB trips are done under pilotage, and you can do that quite easily with a quick plan, a waterproof chart, compass and Breton Plotter.

OK OK, so I do check the GPS constantly, but it is small, not easy to see in bright sunlight and has failed on me a few times with fogging up, loose wiring and once when I forgot to set waypoints and it was too bloody dark and rough to set them when I was out on the water.

My compass is accurate to a few degrees -close enough while bouncing around in a small boat. Would I learn to use a sextant if going seriously offshore? - you bet.

[Tomas]

Originally Posted by Apherel

whatever we do in practice, the ability to work with compass and charts remains an essential skill.

I don't disagree with anything you said (well almost) however .......how many operators out there have any education, tools and practice with course plotting? There has always been a misplaced emphasis on the need for enhanced navigation skills to "cross an ocean". If I leave a harbor on the East Coast of North America headed for the Med., even rudimentary skills and minimal tools will land me somewhere in the vicinity of where I wanted to go. It's hard to miss a continent. After four days in a storm navigating by dead reckoning only, we located Bermuda using an AM transistor radio whose antenna is directional and were only 30 miles off course. The problems begin when one reaches that coastal zone. That is where the ability to navigate is critical.

I gather from reading this forum that at least in UK you have various forms of training; I don't know if they are mandatory or not. These may well include coastal navigation with traditional tools, or not.

My point is that for the majority of casual coastal pilots, a chart plotting GPS is the surest method to insure a safe passage from point A to point B. Not only does it display the boats position relative to its intended track, hazards such as rocks, marks, etc. are shown. If one has "local knowlege" of the area in which he operates and has visual references to guide him to his destination the only tools required are two eyes and a steady hand on the helm. This covers 95% of small boat transits. If on the other hand one is transiting waters of which he has no "local knowlege" and or loses visual references (darkness) or (fog) or (distance from land), then as a responsible "captain" of his vessel, he is required to accurately navigate his course, by one means or another.

Reliability of GPS chart plotters is bulletproof. If one has questionable connections to either power or antennae, "fix it buddy". If one can't read the screen in sunlight he bought the wrong GPS plotter. If one wants to enhance his skills as a small boat operator, do the training in manual navigation and practice those skills. Don't however go screaming across the water in the dark glancing at a bouncing compass and feel that because it says your heading is 135 degrees and a quick glance at a chart says that is the direction to the next pub, that you are navigating a course.

We recently had a 45 ft Catamaran in transit from BVI's to St. Croix, in broad daylight slam into long reef missing the harbor entrance by over a mile. Hmmmm...."the compass said we were going in the right direction?"

[Apherel]

Originally Posted by Tomas

Reliability of GPS chart plotters is bulletproof.

You are absolutely right - The GPS chart plotter is an amazing bit of technology - but like any technology it occasionally craps out - and opens up whole new ways to make mistakes. I've fessed up to mine (and fixed them) - others might like to contribute their GPS stories...

The point I wanted to make is that it shouldn't be seen as infallable, as a technology or as a tool and IMHO one ought to have backups and other navigation / pilotage techniques.

[9D280]

Agreed, any technology (including the compass - remember all your other electrical string on board!) can tell porkies and / or die. At least if it dies, you won't be mistaken into thinking it's still fully operational & telling you the truth. Echoing Thomas' thoughts - Keep a good watch and practice your dead reckoning! Remember - it's not the total rubbish that's dangerous, it's the believable error......

Yeah, "traditional" skills are a good backup to have And if you are taking the QE2 to NY without sight of land for a week and plenty of space to store it all, full astral navigation skills could save you, but in a rib - where do you put all that stuff? I certainly don't have room for a chart table! I do however note bearings & use dead reckoning on a far smaller scale. (Piece of Fablon stuck somewhere convenient on the console & a chinagraph pencil are fab for those wee reminders - dinghy sailors will know what I mean! )

As for the original compass question, I get about +/- 10 degree swing unless its a pankake flat calm, (in which case I can see exactly where I'm aiming for anyway). I have built a fitting to fix my dinghy compass (damped & designed to roll) on the dash to see if it has such a broad swing, but haven't tried it "in anger" yet. I suspect the "compass deviation" is just the effect of a small boat bouncing along in relatively big waves, and if I mounted the same compass on a 6.5m RIB in the same conditions it would be a lot more "stable".... Will post results when I get it out there & test it.

[jyasaki]

Originally Posted by Apherel

You are absolutely right - The GPS chart plotter is an amazing bit of technology - but like any technology it occasionally craps out - and opens up whole new ways to make mistakes.

Having people abandon their chartplotters for whatever reason, and resort to a chart and compass... That sounds like opening up whole new ways to make mistakes...


jky

[Tomas]

Originally Posted by Apherel

The point I wanted to make is that it shouldn't be seen as infallable, as a technology or as a tool and IMHO one ought to have backups and other navigation / pilotage techniques.

I have a Garmain "hand held" chart plotter, GS60 Sx, and with mount and more coverage than I'll ever need with installed BlueCharts for a total of around $800.00. I carry spare batteries and "Yust en Case" I keep a Garmin Trek which set me back all of $59.00 in my dry box as backup. That unit has no charts but does waypoints, tracking, etc. In terms of the Satellite array, it is so redundant it stinks. I receive not only 12 birds on my unit and could navigate off as few as three but one of the twelve is the new tech. bird which gives super accuracy. The GS60 Sx is submersable, crystal clear in the bright sun (I didn't know you had that feature over there), doesn't drink and the stinkin US government has ceased what they used to call "Selective Aquisition" which jammed the signal to degrade accuracy, presumably for military reasons. Commercial and military airplanes use GPS to navigate and in fact Garmin's main business is avionics, not consumer GPS. An added benefit I get here in the land of very deep water is I am able to run bathometic lines of depth when fishing to try to stay over 300' of water. A zig 100 yards one way and one is in 75', a zag the other and you got 3,000.

Oh yea, I've got a compass as well, my good luck charm.

I would never ever argue that less knowlege bests more knowlege but start with the most accessable, easiest to use best technology available and back fill from there.

We're agreeing with each other all over the place!

[Tomas]

Originally Posted by Tomas

crystal clear in the bright sun (I didn't know you had that feature over there)

Oops I failed to note that you're in Australia. Yup, you got sun!

[PeterM]

Most compass are useless in a boat - you have to account for variation & deviation , and after that they will only be accurate if it is level & not in a turn. I would hope that in the UK most 'lost' situations coudl be solved by heading one of 4 ways - north , south , east or west - you end up hitting land in the end.

Unless you can do accurate compass swings most will have no chance - aircraft compass swings take ages ! ( and thats usually with the guide of a large runway to base things on - and they are only to within 5'.

Who actually uses the compass when boating normally ? Very few I guess - only when the GPS packs up maybe ?

Big ships I guess for course corrections , but even then realtive to GPS / plotted position ?

JUst my thoughts ............ every one should however have at least a good idea how to plot a course etc for when things do go wrong ............

[Peter J]

Originally Posted by Rogue Wave

Yep that#s what we use out here but if the leccy fails then you need tohave another compass, I use a lanyard plastimo something. It#s yellow and it cost about 40 quid. always ready and not surounded by wires

Am I right in saying you can always pick up the GPS signal?

Because in the event of electrical failure I think I would rather pay a few quid more and have a handheld GPS to back up the main one rather than a compass.

[PeterM]

Its not just your unit that can pack up - have been occasions when the whole thing has stopped at times . MOD have undertaken trials & blanked signals in the west counrty for hours at a time ................. hard to interupt the north / south pole . BUt yes handheld is well worth it for very little money compared to what they can do nowadays !

[wavelength]

Reliability of GPS chart plotters is bulletproof

until it goes wrong! My allegedly waterproof plotter worked fine until we had a downpour and whilst the screen was ok the keypad locked up completely whilst the plotter went on a journey of its own and scrolled thru every chart in its memory. Replaced by makers with another one which did exactly the same thing a few months later whilst entering the unfamiliar and very busy waters of the Mersey in bad vis and another downpour. That plotter is now living in a box in the garage as I have given up with it and replaced with a different manufacture.
We teach steering to a compass all courses and have courses drawn out from various nav buoys back home on a laminated diagram in the boats. Compass can be checked each trip when local by steering down the leading lights and other known routes.
As for not being able to get round without gps, before we had that it was Decca which was not reliable in various weather conditions and before that we used fast small boats at sea on long trips fishing etc with just the compass and a watch. I dont remember hitting anything then-although a lot of guys from our boat club did manage to end up a long way from their intended destination.
Gps is brill, and I would feel vulnerable without it now that we have all got so used to the accuracy it gives and we have chart plotters on the boats and hand helds a a back up-but life at sea did exist before gps!