View Poll Results: What heading sensing device(s) do you have on your boat? Select all that apply
Traditional magnetic compass 59 85.51%
Fluxgate compass 42 60.87%
Rate compass 23 33.33%
Satellite compass 12 17.39%
None (only use GPS or other) 5 7.25%
Multiple Choice Poll. Voters: 69. You may not vote on this poll

Reply
 
Thread Tools Display Modes
 
Old 09-23-2016, 11:34 PM   #41
Senior Member
 
tpbrady's Avatar
 
City: Anchorage/Wrangell
Country: USA
Vessel Name: Silver Bay
Vessel Model: Nordic Tug 42-002
Join Date: Sep 2012
Posts: 440
I'm with Keith. I am not sure what to call my heading sensor with a Raymarine EVO autopilot. It seems to be a combination of gyro and electronic rate compass. I've got a magnetic compass at the helm but without being diverted by any fingers didn't check the block. On CE I show the magnetic heading from the electronic compass and magnetic COG from the GPS giving me some idea of drift or local magnetic disturbances. It helps in setting the heading on long legs with cross currents or winds.

Now I am going to work on being diverted.

Tom
__________________
Advertisement

tpbrady is offline   Reply With Quote
Old 09-24-2016, 01:57 AM   #42
Guru
 
cappy208's Avatar
 
City: Cape Cod
Country: USA
Vessel Name: Slip Aweigh
Vessel Model: Prairie 29
Join Date: Oct 2013
Posts: 1,005
How I tell where I'm going:
Look out front. Steering mast on pulpit. (Best 'heading sensor' there is in VFR use)

For IFR; 2 Richie wet compass, one digital fluxgate compass, which gives heading to comnav AP at both stations.

GPS cog (which shouldn't be on the list as a compass).
__________________

cappy208 is offline   Reply With Quote
Old 09-24-2016, 03:29 PM   #43
Senior Member
 
Seevee's Avatar
 
City: st pete
Country: usa
Vessel Model: 280 Sundancer
Join Date: Sep 2016
Posts: 248
Quote:
Originally Posted by cappy208 View Post
How I tell where I'm going:
Look out front. Steering mast on pulpit. (Best 'heading sensor' there is in VFR use)

For IFR; 2 Richie wet compass, one digital fluxgate compass, which gives heading to comnav AP at both stations.

GPS cog (which shouldn't be on the list as a compass).
Good points cappy,

I just don't do IFR in a boat, too risky, but if stuck with it a radar would be a must, and at least one good chart plotter, perhaps two. The compass would be the last thing I'd need if I had the above. Don't even use the compass in a plane.
__________________
Seevee
Seevee is offline   Reply With Quote
Old 09-24-2016, 06:34 PM   #44
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 13,288
As I posted before, when turning in confined areas....the compass is your best friend. Seems like everything else responds too slow.....

So in real IFR conditions....it becomes a great tool to turn on if you know your rollout heading.

But other than that...yeah...mag compasses are becoming a thing of the past.
psneeld is offline   Reply With Quote
Old 09-24-2016, 07:04 PM   #45
Senior Member
 
Seevee's Avatar
 
City: st pete
Country: usa
Vessel Model: 280 Sundancer
Join Date: Sep 2016
Posts: 248
Quote:
Originally Posted by psneeld View Post
As I posted before, when turning in confined areas....the compass is your best friend. Seems like everything else responds too slow.....

So in real IFR conditions....it becomes a great tool to turn on if you know your rollout heading.

But other than that...yeah...mag compasses are becoming a thing of the past.
Psneeld,

totally agree, the marine chart plotters are NOT fast when turning. I had an old Standard Horizons that could turn the boat 180d and it would still show the other direction for several seconds.... not good,

But a mag compass without a flux gate or assist isn't a whole lot better as it leads and lags. Once steady, it's fine.

And for the most part we are not doing turns in confined areas in zero visibility conditions... at least not me. I'm not at that level. I've been in the fog several times, but head for shore, operate VERY slow, and don't like it, and wait for it to lift. However, there's always been "some" visibility.
__________________
Seevee
Seevee is offline   Reply With Quote
Old 09-24-2016, 07:17 PM   #46
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 13,288
Sorry but a decent mag compass allows rollout on a good course just fine...practice makes perfect.

Unless fast in rough conditions....

And it is in confined conditions where you need one most of all...

Heck...In the open ocean celestial works.....
psneeld is offline   Reply With Quote
Old 09-24-2016, 07:20 PM   #47
Senior Member
 
Seevee's Avatar
 
City: st pete
Country: usa
Vessel Model: 280 Sundancer
Join Date: Sep 2016
Posts: 248
Quote:
Originally Posted by psneeld View Post
Sorry but a decent mag compass allows rollout on a good course just fine...practice makes perfect.
Might disagree with you a bit... they just are not that accurate until you're steady... and by the time they are steady, most GSPs will give track made good which is way more important.
__________________
Seevee
Seevee is offline   Reply With Quote
Old 09-24-2016, 08:25 PM   #48
Ted
Guru
 
Ted's Avatar
 
City: Campbell River
Country: Canada
Vessel Name: Okisollo
Join Date: Apr 2012
Posts: 509
Something to consider;

Not all magnetic compasses are created equal.
Use a high quality one and it will likely follow the movements of
a vessel at displacement speeds.
I know mine does but they're not inexpensive.

Ted
Ted is online now   Reply With Quote
Old 09-24-2016, 08:36 PM   #49
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 13,288
But they don't lead and lag that much....and I have the aviation training for precession of mag compasses on altitude climbs and decents....

They are fine for the turns as I described and my last job demanded plenty.

Now the ones that hang off your ski jacket zipper...well maybe they aren't good enough....

You don't need a turn down to 1 degree...10-15 degrees for realigning with the channel was good enough. A GPS can't do that till you straighten out with speed or distance.

Even the cheap marine boat ones work well enough....I did it for a living, you?
psneeld is offline   Reply With Quote
Old 09-24-2016, 08:59 PM   #50
Ted
Guru
 
Ted's Avatar
 
City: Campbell River
Country: Canada
Vessel Name: Okisollo
Join Date: Apr 2012
Posts: 509
Quote:
Originally Posted by psneeld View Post
But they don't lead and lag that much....and I have the aviation training for precession of mag compasses on altitude climbs and decents....

They are fine for the turns as I described and my last job demanded plenty.

Now the ones that hang off your ski jacket zipper...well maybe they aren't good enough....

You don't need a turn down to 1 degre...10-15 degrees for realigning with the channel was good enough. A GPS can't do that till you straighten out with speed or distance.

Even the cheap marine boat ones work well enough....I did it for a living, you?
Yep, commercial salmon trolling for almost 30 years. MOST of my compasses would not lead/lag anywhere near 10 - 15 degrees.

Ted
Ted is online now   Reply With Quote
Old 09-25-2016, 03:13 AM   #51
Guru
 
cappy208's Avatar
 
City: Cape Cod
Country: USA
Vessel Name: Slip Aweigh
Vessel Model: Prairie 29
Join Date: Oct 2013
Posts: 1,005
Do you have a heading sensor?

A previous boat I was on had about a 15 degree 'wobble' in the compass it would slew around about 7 degrees either side of your heading without even slowing down. Turned out the magnets inside the quadrant had completely lost their magnetic properties.

I would suggest that if your mag compass isn't 'responding well enough' to steer by then you need to have it 'swung' and compensated. Just taking a compass out of the box may not swing and respond properly. Then again, a cheap compass will never equal a good quality 6" or 8" Ritchie. These little 3" or 4" compass are pretty lame for performance.
cappy208 is offline   Reply With Quote
Old 09-25-2016, 09:17 AM   #52
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 2,307
I see lots of people still equating the heading from some sort of compass, with the course from a GPS. This and another thread got started because the two are different, and it can be an important difference.

I think most of the confusion is because on land, whether walking or driving, course and heading will always be the same because you don't "slip" on the ground as you walk or drive - at least not under any normal conditions.

In contrast, on the water and in the air, cross winds, cross current, etc can be pushing the boat sideways while at the same time you are steering and propelling the boat by it's motor. Your actual geographic track is a combination of the two.

In a boat, and using boat terminology, The direction that you are steering your boat, which is the same thing as the direction the boat is pointing, is the Heading, and is measured by a compass of some sort that is fixed to the boat. A GPS (excluding sat compasses) is not able to measure that, at all, under any circumstances.

The progress that a boat makes, geographically, is it's course, or more precisely Couse Over Ground (COG). This is what a GPS measures, by noting successive geographic locations, and "drawing" lines between them. Is the same way that a GPS can't measure heading, a compass can't measure COG. So these are different and complementary devices.

As an aside, when I say "GPS", I don't mean a chart plotter. I mean the GPS device that listens to the sats and reports lat/lon, COG, SOG. That might be stand-alone, or it might be built into your chart plotter.

Now in many cases people simply ignore the difference between HDG and COG, and make whatever steering corrections are required to get where they want to go, and that's absolutely fine. And that's because under lots of situations, probably the majority of situations, COG and HDG are the same or very close since there is very little cross current or cross wind, and of course this encourages people to simple equate the two.

But regardless of how much you distinguish between HDG and COG when operating your boat, it can't hurt to understand the difference, especially when you find you boat pointing 20 degrees off from where your chart plotter says you are going...And the difference really matters a lot if you want to have a better understanding of your nav electronics and what each component does, and why it's important.
__________________
www.MVTanglewood.com
twistedtree is online now   Reply With Quote
Old 09-25-2016, 10:56 AM   #53
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 2,940
Good point. Often heading and course are mixed up, and they are not the same. I'm guilty of being a bit sloppy with the terms sometimes.

So on my rig the sources are:

Heading: Mag compass and AP fluxgate.

Course: Furuno plotter and laptop with CE, both calc'ing course from multiple gps fixes.
Ski in NC is offline   Reply With Quote
Old 09-25-2016, 11:08 AM   #54
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 2,307
There's an excellent example distinguishing between the two. Thanks for making it.
__________________
www.MVTanglewood.com
twistedtree is online now   Reply With Quote
Old 09-25-2016, 12:42 PM   #55
Senior Member
 
drb1025's Avatar
 
City: Bellevue, WA
Country: USA
Vessel Name: Vamos a Ver
Vessel Model: DeFever 46
Join Date: Oct 2012
Posts: 424
After installing active fin stabilizers, the HDG and COG were routinely different by 10 or more degrees when the stabilizers were active. The autopilot would compensate by adding more rudder. To twistedtree's point, the difference in HDG and COG indicated a problem with the stabilizers steering the boat. A simple adjustment by the installer fixed the issue.
__________________

drb1025 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 01:18 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012