Using the compass or not?

CAVU":1uw0vkwm said:
Tom, I have a Furuno unit without mapping capability, but I thought they all worked the same. I believe they require the boat make some headway for a certain distance before they can compute which direction you are going?
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Yes - that is the case. Unless the boat is moving (RELATIVE TO THE SATELLITES), there is no way to compute direction. Hence, if one is at anchor, or otherwise disabled, the compass reading of the GPS is useless. I can imagine a circumstance in which I was drifting in the fog, and would want to know the direction something else was relative to me (like a fog horn or a buoy bell).

That said, I still only have a small handheld compass on board for emergency backup cases. I have a fixed mount GPS AND a handheld back-up unit. Ditto for the VHF radio. I also make sure that I have PLENTY of extra batteries for the handhelds (and that they are reasonably fresh - just re-stocked the boat). As a few have pointed out already, redundancy is a good thing. Yes, redundancy is a good thing :lol: . I have had my CD22 for 3 years and have been out on some very foggy days - haven't yet needed the compass but am glad it is there.

The URL provided by Fred/Robin (http://cnn.netscape.cnn.com/ns/news/sto ... PO&coview=)
discusses the possibility that the GPS system might get turned off during an attack on the US. That makes me think I should have a back-up compass. However, in practice, I've never been more than 2 miles from some shore (hope to change that this spring with some halibut adventures). My biggest fear to date in the fog is getting run down by a freighter. GPS, maps and compass won't help with that - radar would be nice but right now, can't justify the $'s. Hence, in fog, I stay well out of the shipping lanes or don't go out.

Roger on the
SeaDNA
 
Roger,

The GPS will still point you to the waypoint with a course and distance even if you are not moving. So if you set a waypoint near the bouy or light, you will know how far away and in what direction it lies and you can use a magnetic compass to determine direction until the boat is moving again.
 
I like Dan's post. Points out that some may leave shore without a compass (at least a mounted one) but then he relates a number of good reasons why he personally relies on that compass. I boat all over the Great Lakes in my 19 foot boat. I have two permanently mounted compasses in the boat. (3 1/2 inch direct read card at the helm and another 2 inch front read compass mounted on the dash where I can see it from the back of the cockpit when fishing and someone else is steering). I also have a mounted GPS and an extra handheld GPS and my pocket PC has GPS as well. My keychain has a compass and so does my tackle box. Guess I am easily confused, but I like to know what direction I am headed before I put it in gear, real foggy or unfamiliar waters at night, etc.

I was in the Coast Guard Auxilliary for a number of years and taught classes on navigation and compass. I have swung ship on my own boats and have done it in an amateurish way on other boats as well. I run a string from bow to exact midpoint on stern. Then I run another string parallel to that one through center of wheel, helm seat and compass. Used to run marked courses to swing ship but now use GPS.

A couple of other hints (borrowed from Chapmans or other books or experienced boaters over the years). When you buy a compass check it on the store counter. I don't care if it is off a couple of degrees as that can be adjusted. I bring my pocket knife or some other metal close to the compass and see how far it deflects and how fast it settles. Then remove the knife and see how fast it returns and how quickly it settles. You will see a variation in same compass from same manufacturers. Most compasses also have an opening to add fluid. Sometimes air bubbles will develop in a compass (although the better ones with rubber diaphrams seldom exhbit this) particularly if the boat is stored outside in Midwest winters for instance. The fluid is merely mineral oil. It make take a couple of times to open the screw hole, add oil, replace screw and check to see if all air is out, but it can be done.

I say 1. paper charts, 2. compass, 3. GPS on list of navigation essentials. The extent to which you can use and rely on the GPS-Chatplotter, etc., to replace the chart and compass depends on the quality and reliability of your GPS and your skill in using it. But keep at least a small scale paper chart and a $3.00 compass on board as well.
 
Amen to the sentiment behind "Don't leave home without it" and beyond that, do what you need to know how to use it if you need it. GPS is good, but fallible in oh so many ways. Together with a compass, mighty good. Together with someone who knows how to use both well, mighty, mighty good.
 
I too like Dan's summary.

A postscript to the above comments;

A cruise ship hit rocks off the East Coast of the USA because the GPS antenna wire was damaged and the auto pilot couldn't tell that the GPS location had not updated.

Navigation occurs in the mind of the navigator. Be sure your mind is engaged and alert to the changing conditions.
 
Just a compass related tale.

We've got a second home in DownEast Maine, about 70 miles from the Canadian Border on Little Kennebec Bay. Great spot on the lower Bay of Fundy, 17 feet of tide, when it goes out, it goes waaaaaaay out :shock: . Lots of lobstering, scalloping, etc. Many friends with lobster boats, etc. A good friends son wanted a GPS and didn't know how to mount/use it so I negotiated a deal with him to trade cost for "lobster futures". At $2.75 a pound :P , it was a good deal. He had a 34ft DownEast Hull Lobster boat with a Cat Diesel, nice stable boat. When I got there to install the GPS, he asked me if I knew anything about compasses :?: .

What's to know, I thought. Only one moving part, no power unless they have illumination. Seems he'd been navigating without one because he couldn't get it to behave correctly, always pointed SE no matter what direction he was going :disgust . Amazing that he was even alive given the fog conditions on the coast of Maine and that he'd been fishing for a couple of years, sometimes single handed.

Anyway, I got down there to mount the GPS and noted the compass (pointing to SE, just as he said) just forward of the helm on the stbd side. I also noted some black boxes on either side of the compass. When I enquired as to the function of the black boxes, he turned on the stereo and showed me that they were speakers. :smileo

I moved them over to the port side of the boat and the compass immediately swung over to NE which is where it should have been pointing. "Dagnabbit" he said (or words to that effect), why'd it do that? I explained about magnetism and how a magnetic compass worked. Finally got through.

Installed the GPS, trained him for a couple of hours, (retrained him each summer since too) and he was a happy camper :D .

Sally and I were too, the GPS cost me $350 which bought me 100# plus in lobsters over the next couple of years. Couldn't bring myself to charge him anything for installation or training. He's now a competent navigator, can come in and out during fog without endangering his life. His Mom and Dad were happy too!

A compass is important! Understand how it works and how to use it!!!! :lol:
 
I have been looking for compass, magnetic, the will mount overhead, and read from the side closest to the helm seat. Wondering if anybody has any recommendations for a good compass that will fit that application? I am wanting to install a backup to my fluxgate electronic compass.

Harvey
SleepyC :moon
 
I concluded, after a couple of disconcerting episodes, that it was well worth the time to sit down and figure out the sources of all the various types of information displayed on my chart plotter AND how it is that I might detect failure of any of those sources. The Raymarine system actually reports some of those (ex., Loss of Heading, etc.) although it's not always obvious what the true source is. More important, still, is having the means to determine the significance of that loss and, if necessary, to be able to substitute some other source.
I now routinely set the electronic (flux-gate) compass to display increments of deviation from the selected compass heading at every change of course heading even though the plotter is set to display compass heading and cross-track error. I use the e-compass for maintaining (and corrrecting) heading and the chart display for current position and potential conflict (radar) information.
The GPS-derived heading info on the chart plotter responds too slowly to be of much use for holding a heading especially at low speeds.
And I have a magnetic compass mounted close to line-of-sight behind the e-compass as a secondary reference when visibility outside becomes questionable.
So far, so good; until someone offers a better scheme.

Paul Priest
J.C.Lately
Sequim, WA
 
hardee":1ameyayw said:
I have been looking for compass, magnetic, the will mount overhead, and read from the side closest to the helm seat. Wondering if anybody has any recommendations for a good compass that will fit that application? I am wanting to install a backup to my fluxgate electronic compass.

Harvey
SleepyC :moon
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HARVEY-

Veeeerrry Interesting!

!. Most of the magnetic compasses large and accurate enough to use in a boat are designed to be either looked down upon (flush mount, surface mount, or binnacle mount) or are designed to dash mount on a vertical surface. I don't know of any upside-down models.......(?) You could use a dash mount in a custom mount hanging from the ceiling, but....... (read on below)

2. In any case, you need to be behind the compass to read it accurately, at least to get the same numbers your flux gate will be giving you. The compass card stays "fixed" in the earth's magnetic field as the boat changes headings and rotates about it. You'd have to put it in front of yourself, and in a position to impair your visual field in a C-Dory cabin.

What to do?

If I were racing a sailboat, I'd put it out in front of my visual field on the cabin trunk in front of the helm, so I could read it with as little visual deviation as possible from my course underway. This however, on the CD, would entail putting a compass in a housing mounted on the trunk directly in from of the starboard helm window, and far enough out to be free of the magnetic field of the permanent magnet DC windshield wiper motor(s). (A plastic or even a truly non-magnetic stainless steel bowl turned upside down works great.) You'd also have to provide a cover for the compass when it wasn't in use to protect it from sunlight, etc. (Would look cool at night with red LED lighting.)

Wait a minute! This is getting complic.....:smileo

KISS Principle rescue me! :cry

Joe. :lol: :thup
 
Main system is Raymarine C-80 with radar
Backup 1 is iPhone 3G with Navionics app/chart (I like this)
Backup 2 is a handheld VHF with rudimentary charting and GPS (kindof old now)
Backup 3 is a handheld compass
 
When we lost power to the nav system in the San Juans we found the abilty to take bearings using the binoculars built in compass more helpful than the just using main compass.
 
I'm reading about the probability of GPS failure. Yes it happens but you ever have your compass point you the wrong direction?

I was on the North side of Isle Royale when the GPS said to go one way and the compass said another. Visual references confirmed the Compass was wrong. I moved the boat less than a quarter mile and the compass rebounded and was in agreement with the GPS again. I'm no geologist but the hefty iron/oar deposits in the area may have some thing to do with that and may explain the high number of ship wrecks that pepper Isle Royale.

It was a humbling experience. I totally understand how big boat can plow into the shoals in low visibility. That had me and my buddy on edge when the fog rolled in a couple of days later. It really made us slow way down and be a little more deliberate with our navigation.

Chris Bulovsky
 
All mechanical/electronic things have problems. But, if you understand those problems and work with them they're wonderful. If they don't, you better have a Plan B.

Your chart plotter/GPS gives absolute position: here is where you are supposed to be and here is everything else that's supposed to be there.. A compass gives relative direction to North. A radar will give you what is needed most relative position: here is where you are relative to that island/ship/whatever. It's the only instrument that can see through fog or darkness. To do a good job all the time you need to use them all. Just look at all the wrecks caused by fog, wrong dead reckoning and bad guesses before we had those instruments.

And if they malfunction, you need to have the knowledge to recognize that and go to plan B. That's where pager charts and a compass come in. Its not that they're the best thing to use, but they're certainly the most dependable.

You just have to know what to use when. And you'd better have the correct stuff on board for the right situation. That includes a compass and paper charts.

I'm not sure why I wrote this, but Chris' note started me. Chris, you're to blame for this post, unless you already have a radar.

Boris
 
No radar yet Boris. As much as I would like to drop some coin on fabulous electronics my budget has limitations. Yeah I could probably could sacrifice my other hobbies/passions but that lead to deep depression and subsequent visits to mental health wards and the cascading bills all ending in a failed marriage........then I 'll living in a "VAN DOWN BY THE RIVER"well you see my point. This all over a Radar unit. :lol:


You tube the "Van down by the river" if you don't get the joke! :D


Chris Bulovsky
 
Chris, I'm sorry about that comment. Blame it on old age and getting my truck running, neither of which I want.

The subject of "all the modern equipment we use, and I'm gonna get rid of my compass and charts" just gets me going, not that that's what you posted.

Though radars are cheap, $1300. And I'm incoherent, and that truck
will run today.

Boris
 
The previous owner of TripleJ was active Coastguard, so it pleased me that smack dab in front of the wheel was a nice big compass. Even though my chart platter is right there along side, once I have established a barring I use the compass. I find it easier to maintain a true course this way, the lag time associated with the GPC has me all over the place…especially in fog.
 
I would not rely on my i phone G3 as a back up--the GPS is not accurate enough. I have also heard stories that when at sea, and in Mexico etc the positions are even worse than when near cell towers. It sort of puzzles me why apple does not put a better chipset in the i phone.

As for a back up compass, I like the hockey puck type--it is a very accurate hand bearing compass, as well as being readable from over it.

As for an overhead compass--the "Tell tale" type of compass is what is needed, but you cannot easily offset the reading.

comtt02.jpg


As beautiful as these are, they are not really practical for reading a course, especially from one side.

There are definately times when a compass is a life saver. For example one time we had to "cut and run" from an anchorage in almost zero visability--It was before chartplotters, but even with a chart plotter, the delay of a bearing could have been fatal. The pre-determined compass course took us right out of the harbor into the safety of the open sea. It is always a good idea to take a bearing to safety--as well as how the boat is lying at anchor when you bed down for the night.
 
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