Compass 101

[Mario S Caner]

Originally posted by Mario S Caner
Compass Balancing

...the needle will only be off balance slightly. The variance will get bigger as you go further, and in extreme cases the compass can stick....

The key words here being off balance everyone, which basically means "tilt" not direction. With modern day off-shore electronics being as inexpensive and as reliable as they are, even the oldest and smallest of vessels can and (for the most part) have been outfitted to be able to operate safely.

For divers, navigation is entirely different. Unless you are using a compass/computer-variant electronic device to navigate in water, you still rely on old school navigation principles. I for one get bored with the basic reciprocal back and forth dive. Figure 8's let you see more.

One other thing to consider is that Navigation is vastly different for all of us. An open water, cold, low viz dive where the topography never seams to change can't really be compared to a tropical water dive that looks like you're diving in a big puddle of Evian. So techniques change considerably. Where the Blue Water diver may just kick out one way, consume 1/3 of his/her air supply and then turn around and head back into the vicinity of the boat. They are most likely helped by the 150ft viz, and can find their way back mearly by, "oh, there's the boat way over there" mentality. Where as a Green Water diver has to keep track of heading and approxiamate distance much more closely to be able to surface by the swim-step.

 

[TwoBitTxn]

I'm now unconfused but I still think Joe is an unbalanced regulator.

So its possible if Ontario diver bought a compass locally he may have a problem if he wanted to dive in Australia?

Tom

 

[Warhammer]

Well, Joe, us backwaters folks must stick together when comes to our smog infested brothern ya know.

And Mario, a figure 8? Interesting, you'll have to show me that one bro. Heck, I started out going to navigate a triangle a while back, then got confused on calculating the distance of the hypotenuse and said, "The hell with it, the boat is over yonder somewhere.".

 

[Mario S Caner]

Tom, Yes, if your friend has an older or an inferior compass the needle may dip too much to give reliable reading or even lock up all together.

Warhammer, I am the [red]Master[/red] of the figure 8. I'd be happy to show you.

 

[Kane(adian)]

My post had nothing to do with yours. I was only commenting on what Omar had said. Whether it was off the original topic could be debatable. Did my post have to do with accurate navigation? I think so. Did the original post have to do with accurate navigation? I think so.

 

[Rick Murchison]

Omigod!
I missed the point that Kane(adian)'s point wasn't in response to my point after all, making my point pointless and his... pointed?...
Ah, well, back to the point... what was the point, anyway?
Rick

 

[Ontario Diver]

Rick:

The point is that the point doesn't point north, it points to magnetic north and the number of points between the pointing to of mag north and the point we call true north is declination (as a point of order).

But if I purchase a compass in Canada at a point of sale terminal, and then fly to some where else, does the point of "magnetic dip" affect the pointing of the pointer at some foreign point? From my point of view, the use of iron points to force the north pointer to be corrected for better pointing, is usually restricted to expensive navigation compasses(ie.for ships and aircraft). and primarily to correct for the mass of metal that surround the north pointer. I don't know if vendors see the point of doing this expensive thing for cheap compasses.

But if you are pointing you compass towards a point below you or a point above you than the point is that the point will not point true because the card is balanced on the point of a needle and if the card drags on the bottom of the compass then the pointing is pointless. Which is the point of needle (point) drag.

But I think that many posters are pointing out that much of this is pointless because we use the compass to point in constant/fixed direction rather than navigation from point to point. (By the by, being off by a degree will move you off course about 1m in 100m - If I remember my Army days; so I think you'll get more error from the current than from the use of the compass)

But to answer Tom's point, I will gladly take point on a dive off a point in Australia to check the compass point on a point to point navigation to prove the point. But I don't have enough Frequent Flyer Points.

 

[jbd]

of making me :loopy: I've never heard the word point used so eloquently to make a point. Really enjoyed the reading Ontario Diver

We need to put Ontario Diver in the hall of fame with Walter.

 

[LesleyDSO]

we all got the point?

 

[jobowker]

I'm not too concerned with declination and that sort of stuff when it comes to diving (on the boat I use a GPS or two) but there are two factors that I DO care about when it comes to compasses (since I can get lost down there and surface 1/4 mile form the boat in the middle of a channel). First, If I don't hold my compass fairly close to level, the compass card sticks, and I'm really not going the way I thought I was, and two, there can sometimes be huge local variances due to large submerged metal objects, like wrecks & things. I no longer take a compass reading while sitting next to the anchor, either.