Do you have a heading sensor?

[O C Diver]

When I participated in the poll, I entered "Rate compass" before I actually read the question and saw "Select all that apply", and there is no way to correct after the fact. 4 fingers of scotch does that to me.

I actually have Rate, Fluxgate (standby) and Magnetic compasses onboard. I wonder if I'm the only participant that did that

+1

Ted

 

[twistedtree]

So we definitely have some polling errors, which is probably true of every poll.

Does anyone want to fess up to not having a traditional magnetic compass, aka a whiskey compass?

Any by the way, where does the term "whiskey compass" come from? Would people use whiskey as the dampening fluid? Or is it something else? I had never heard the term until this thread.

 

[psneeld]

So we definitely have some polling errors, which is probably true of every poll.

Does anyone want to fess up to not having a traditional magnetic compass, aka a whiskey compass?

Any by the way, where does the term "whiskey compass" come from? Would people use whiskey as the dampening fluid? Or is it something else? I had never heard the term until this thread.

Me either ...not in the USCG or baby boat commercial world. Will be interesting....

 

[Codger2]

When I participated in the poll, I entered "Rate compass" before I actually read the question and saw "Select all that apply", and there is no way to correct after the fact. 4 fingers of scotch does that to me.

I actually have Rate, Fluxgate (standby) and Magnetic compasses onboard. I wonder if I'm the only participant that did that

I did too , Larry but in my defense i only had 3 fingers of scotch!

 

[LarryM]

I did too , Larry but in my defense i only had 3 fingers of scotch!

3 fingers, 4 fingers . . . could this be the real origin of term "Whiskey Compass?"

 

[LarryM]

So we definitely have some polling errors, which is probably true of every poll.

Does anyone want to fess up to not having a traditional magnetic compass, aka a whiskey compass?

Any by the way, where does the term "whiskey compass" come from? Would people use whiskey as the dampening fluid? Or is it something else? I had never heard the term until this thread.

A quick Google search found:

"One theory out there about why the standby (magnetic) compass on an airplane earned the name whiskey compass is that the name served to remind a pilot to refill a compass that lost its fluid with whiskey and not water because of its lower freezing level. Supposedly this is when airplanes lacked pressurization and heating."

"Another theory says that the standby compass is filled with kerosene earning the name Wet Compass. In aviation Phonetics, Whiskey is for W, explaining Whiskey Compass or W-Compass."

 

[Peter B]

Magnetic compass at both helms, compass in autopilot, compass in chart plotter, compass in each of our smartphones. Oh and I forgot the compass in the binoculars.

Like the man with 2 watches...he never knows the exact time!

So...you could say, a pretty all encompassing set-up..?

 

[koliver]

I haven't responded to the poll.

1 I have never heard of a "rate compass" until this thread. I doubt that i have one.

2 I have heard of a "Fluxgate compass", but when I look up "Raymarine Autopilot" to confirm that mine uses a Fluxgate, their site describes only their latest offerings, and calls the heading sensor a "Digital Compass".

3 I have never heard of a "Sattelite Compass". I expect that term to describe the directional information your GPS displays, but that information is only available when your GPS is in motion, so really isn't a compass.

4 I have a compass app on my phone, but it is again only a clever electronic means of displaying direction. It doesn't seem to need to be in motion, but it gives such a wide range of erroneous readings that it shouldn't count at all.

5 To have a proper "heading sensor" from your GPS, at least 2 separate GPS are required. Then when you are not in motion, the plot of the relative positions of the two receivers can be used to determine your heading. This is still not a kind of compass, but is a true "Heading Sensor". I don't have one.

I do have several magnetic compasses. I rarely refer to any of them.

I usually steer by using my autopilot to maintain heading along a route shown on my chart, displayed on my laptop screen. I think my autopilot refers to a fluxgate compass for its diretional information, and I know the chart program accept input from my GPS, so both of those are used at the same time. sometimes they even agree!

 

[twistedtree]

I haven't responded to the poll.

1 I have never heard of a "rate compass" until this thread. I doubt that i have one.

2 I have heard of a "Fluxgate compass", but when I look up "Raymarine Autopilot" to confirm that mine uses a Fluxgate, their site describes only their latest offerings, and calls the heading sensor a "Digital Compass".

3 I have never heard of a "Sattelite Compass". I expect that term to describe the directional information your GPS displays, but that information is only available when your GPS is in motion, so really isn't a compass.

4 I have a compass app on my phone, but it is again only a clever electronic means of displaying direction. It doesn't seem to need to be in motion, but it gives such a wide range of erroneous readings that it shouldn't count at all.

5 To have a proper "heading sensor" from your GPS, at least 2 separate GPS are required. Then when you are not in motion, the plot of the relative positions of the two receivers can be used to determine your heading. This is still not a kind of compass, but is a true "Heading Sensor". I don't have one.

I do have several magnetic compasses. I rarely refer to any of them.

I usually steer by using my autopilot to maintain heading along a route shown on my chart, displayed on my laptop screen. I think my autopilot refers to a fluxgate compass for its diretional information, and I know the chart program accept input from my GPS, so both of those are used at the same time. sometimes they even agree!

A "satellite compass" is what you describe in (5), plus some other stuff to make it work better.

 

[Ski in NC]

Four sources:

Fluid damped card compass
AP 35 with rate compass
Furuno GPS chart plotter
Laptop with Coastal Explorer and hockey-puck gps antenna

All are within a few deg of each other in calm conditions.

 

[tpbrady]

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

 

[cappy208]

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).

 

[Seevee]

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.

 

[psneeld]

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.

 

[Seevee]

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.

 

[psneeld]

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.....

 

[Seevee]

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.

 

[Ted]

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

 

[psneeld]

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?

 

[Ted]

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

 

[cappy208]

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.

 

[twistedtree]

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.

 

[Ski in NC]

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.

 

[twistedtree]

There's an excellent example distinguishing between the two. Thanks for making it.

 

[drb1025]

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.