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Old 03-03-2014, 11:52 AM   #21
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I find it much easier to steer by compass in thick fog. Crossed half of Dixon Entrance in the fog. Had the GPS on of course (and radar) but to steer a straight course the compass was a better tool. It's one of those things you've got to get the hang of too. I considered it a challenge and a good thing to know. Gotta watch it constantly though.

Whenever visibility disappears (or looks like it may) I use the compass as a reference point. If all else fails I have the ability to continue on the course that I was on. Sometimes I make a note on paper of the course so I can always return to it w the compass.

I'm fortunate enough to have a compass w just the right amount of stability. The compass I have is the only really useable compass I've used.
Likewise. In addition, the compass shows directions even if the boat is not in motion, unlike COG provided by the chartplotter.
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Old 03-03-2014, 11:55 AM   #22
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For running a Predicted Log race according to the rules, we must use our compass. At all other times, we use GPS. As an aside, it now costs the price of a new compass to get it professionally boxed. My bridge compass is starting to stick and the company Aquameter is no longer in business so no parts are available. I'm goin' to take the compass from the lower helm and install it on the fly-bridge where we do all our pilotin'.
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Old 03-03-2014, 12:06 PM   #23
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Greetings,
Mr. RW. couldn't help but notice "AREA OF MAGNETIC DISTURBANCE". Is the cause for this known and does it affect the compass much?
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Old 03-03-2014, 12:06 PM   #24
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I use a hand-held compass and compass binoculars for bearings. I do scan the helm compass as I do other instruments, and I do report the course reading when I turn over the helm to someone. But do I actually use it for navigation? Honestly, not really, as most of the time the auto pilot is steering. Would never get rid of it as it is a fundamental of navigation, has few moving parts, and doesn't require electricity.

It is a legal requirement in Canada to have on boats over 8m. If under 8m it is not required if you are using navaids, i.e lake, river or canal boating.
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Old 03-03-2014, 12:49 PM   #25
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Greetings,
Mr. RW. couldn't help but notice "AREA OF MAGNETIC DISTURBANCE". Is the cause for this known and does it affect the compass much?
I can only guess based on the geology of this area ... iron rich granite at the bottom of the river canyons.

It does affect the compass and the deviations are random and significant ... luckily, there is plenty of nav aids and topo points to stay on track.
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Old 03-03-2014, 12:59 PM   #26
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Greetings,
Mr. RW. couldn't help but notice "AREA OF MAGNETIC DISTURBANCE". Is the cause for this known and does it affect the compass much?
Don't have charts for that area loaded...unless there's something else in the chart notes...the underwater cables nearby can also set up a disturbance.
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Old 03-03-2014, 01:02 PM   #27
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Coincidental ... there is plenty of cables between various islands there and no marked disturbance, and other marked disturbance areas and no cables in sight.
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Old 03-03-2014, 01:08 PM   #28
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Coincidental ... there is plenty of cables between various islands there and no marked disturbance, and other marked disturbance areas and no cables in sight.
Depends what they are as I have seen anomalies from cables...but here's an interesting bit of info (probably not cables for sure)

Magnetic Anomalies - Kingston , Ontario waterfront

28) Local magnetic disturbances.-- Differences from normal variation of from about 006 W to 007 E have been observed at numerous locations throughout Lake Ontario. Differences of up to 37 have been observed in the approach to Kingston, Ont., on the N side of the head of the St. Lawrence River. The locations of these anomalies are shown on NOS chart 14500.

Another reason to either really use your compass...or NOT!!! You definitely have to plan for all these little issues...or be way off...





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Old 03-03-2014, 01:36 PM   #29
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Like most of us, I use my GPS, but I look at my compass as well. I always think about if GPS is taken down or significantly degraded for security purposes, or due to a failure or a hack--? I like to think my compass is pretty necessry.
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Old 03-03-2014, 01:47 PM   #30
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Greetings,
Messrs. RW and psneeld. So what you're both saying is that there is SOMETHING down there and we shouldn't necessarily take it for granite. Bwahahahaha.....Sometimes I just knock myself out.....
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Old 03-03-2014, 01:49 PM   #31
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Another reason to either really use your compass...or NOT!!! You definitely have to plan for all these little issues...or be way off...
... or autopilot ... another note in the link you provided:

Using autopilot heading east (toward Fort Henry) 200m off the shore out of Portsmouth is liable to be very exciting. Just off the water plant, expect your boat to steer sharply toward the rocks! Whoopie!

I am going to test it this season. The declination map off Kingstone shore goes into my Nav Folder ... thanks!

Quote:
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Greetings,
... there is SOMETHING down there and we shouldn't necessarily take it for granite.
The article suggests a deposit of magnetite (iron oxide) which is a magnet itself:

One way to picture this is to imagine an underground deposit of magnetite that runs deeper towards the East.
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Old 03-03-2014, 03:41 PM   #32
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I have two compasses and seldom look at them.

A funny story from the 1970's when I was stationed in AK. My boss and three others of us took his boat to Whittier and Prince William Sound to do some bear hunting. At least that was our excuse to spend a few days on his ~28' boat.

We were headed back across about a 15 mile stretch of open water. We had rough calculated our compass heading and set out. It started to rain and there was a fairly heavy fog so we flipped on the wipers. I was driving and congratulating myself on being able to hold the course so well. Pretty soon we started seeing small ice bergs and we hadn't seen any on our way out of Whittier.

We kept going because the compass said we were still on course and eventually we encountered a small crabbing boat. He laughed when we told him we were headed to Whittier. Apparently we'd made a slow turn to STBD and didn't realize it, and were about 25 miles north of where we should have been.

Seems the electric field set up by the wiper motors had frozen the compass on its "then correct" heading and we didn't realize it. No matter what direction we turned, the compass never moved.

It took us about two hours to get back to Whittier and we got there just in time to load the boat on the train and make it back to the highway to Anchorage. (That was before there was a road through the tunnels).

I've always said "Ya gotta be smarter than the equipment you're trying to operate." That day we weren't.
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Old 03-03-2014, 04:48 PM   #33
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... or autopilot ... another note in the link you provided:

Using autopilot heading east (toward Fort Henry) 200m off the shore out of Portsmouth is liable to be very exciting. Just off the water plant, expect your boat to steer sharply toward the rocks! Whoopie!

That's pretty funny. There are actually a surprising number of places throughout the Great Lakes where the compass goes wonky, particularly Georgian Bay. Back in the day before GPS when everyone "had to" steer by compass, these areas were all well known locally and taken into account. Decades later these anomalies are being "re-discovered" by a generation who haven't a clue how to use a compass but are quickly finding them the hard way with their autopilots. I suppose this too shall pass with the advent of GPS compass's.

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Old 03-03-2014, 04:56 PM   #34
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If your autopilot is running off your GPS (as most do), the anomaly near Kingston, ON will have no effect.

I use it all .... compass, hand bearing compass, pelorus, paper and GPS just to keep myself tuned up. I've had several electronic failures in nasty situations on deliveries. It's a good idea to keep skills with all methods of navigation up to speed.
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Old 03-03-2014, 05:25 PM   #35
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Three or four times in Alaska we've been running along and noticed the curser (diamond shaped thing that represents our boat on the chart) well off on land. It's always happened when I could still see the rocks on the chart and where we were going. It must be the results of a magnetic disturbance. Is that correct?

Is "curser" the right name for the diamond like thing in the middle of the plotter?
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Old 03-03-2014, 05:28 PM   #36
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Three or four times in Alaska we've been running along and noticed the curser (diamond shaped thing that represents our boat on the chart) well off on land. It's always happened when I could still see the rocks on the chart and where we were going. It must be the results of a magnetic disturbance. Is that correct?
Magnetic disturbance does not affect chartplotters/GPS. Scale does. When you see this happen again, change scale and you will see a notable difference.
While GPS signals are incredibly accurate, their relationship to charts is sometimes inconsistent. Lots of stuff online about this issue.
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Old 03-03-2014, 05:38 PM   #37
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............ While GPS signals are incredibly accurate, their relationship to charts is sometimes inconsistent. .
And it's possible for the charts to be incorrect as well. I've run the boat on what the chart shows as land before. I would say it's best to believe your own eyes, then the markers and then the plotter.

The depth sounder trumps them all.
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Old 03-03-2014, 05:48 PM   #38
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Like these two photos taken within seconds of each other.
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Old 03-03-2014, 05:48 PM   #39
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I use it to check wind direction or how the boat is lying at anchor. Use it all the time fishing. If a piece of structure shows off to the east on the plotter, I use the compass to steer east until the GPS catches up. The GPS rules on long distance runs though.
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Old 03-03-2014, 07:51 PM   #40
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GPS is more accurate than charts.
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