Compass skills?

[tracydr]

I feel really bone-headed about this but I am just not getting my compass skills down as well as I should. I think part of the problem is that my land nave in the Army used a slightly different style of compass and I just can't seem to make the conversion. Also, my OW was way back in 1995 and my husband, who has taught my AOW, rescue and is now teaching my DM has made the reasonable expectation that I already have the basic navigation skills. I've had good enough skills to muddle along and pass AOW and Rescue but simply don't feel fluent yet.
Is there anything better than my PADI books that I can read on using my dive compass? I really want to be proficient enough to lead night, shore dives, etc. I used toe quite good at land navigation so I'm not quite sure what's happened.

 

[fnfalman]

I feel really bone-headed about this but I am just not getting my compass skills down as well as I should. I think part of the problem is that my land nave in the Army used a slightly different style of compass and I just can't seem to make the conversion. Also, my OW was way back in 1995 and my husband, who has taught my AOW, rescue and is now teaching my DM has made the reasonable expectation that I already have the basic navigation skills. I've had good enough skills to muddle along and pass AOW and Rescue but simply don't feel fluent yet.
Is there anything better than my PADI books that I can read on using my dive compass? I really want to be proficient enough to lead night, shore dives, etc. I used toe quite good at land navigation so I'm not quite sure what's happened.

The numbers placement on a dive compass is reverse of the Army land nav compass, but the principles are the same. Since that you don't shoot your azimuth like you would with your lensatic compass, the number placement is reversed so that you can easily see it.

The North arrow still points north, it's just that 0-degree is now at the 180-degree position instead of at the 0-position that you are familiar with. This way you can look through the little window (in photo below) and shoot an azimuth that will have the correct reading. Imagine if you were to shoot an azimuth with the underwater compass by looking through the little window and try to go for 0-degree. If 0-degree were at its actual place then you wouldn't see it through the window. 180-degree would show up in the little window. See what I mean?

Otherwise, the principles for using the compass is the same as land navigation - intersection, resection, etc. Don't forget to use terrain association as well. Look for distinctive boulders, kelp patches, etc.

I

 

[fnfalman]

Look at the numbering layout between UW compass and land compass.

0-degree is at the due South position of the UW compass and 0-degree is at the due North position on the land compass. The layout is like that for the same reason I've said above. Top compass is UW and bottom compass is land.

 

[Roko]

One thing to watch out for in underwater nav, is that not all compasses are created equal...

I had a compass which, if not held perfectly flat, "north" would migrate down to the lowest point.. It wouldn't just jam up, north would actually go to wherever the compass was tilting. Now, all compasses need to be held close to level, but a proper compass SHOULD NOT migrate if tilted slightly.

Needless to say i turfed that one, the current compass I use does not have that problem, and holds true even if tilted slightly.

 

[fnfalman]

One thing to watch out for in underwater nav, is that not all compasses are created equal...

I had a compass which, if not held perfectly flat, "north" would migrate down to the lowest point.. It wouldn't just jam up, north would actually go to wherever the compass was tilting.

Needless to say i turfed that one, the current compass I use does not have that problem, and holds true, even if tilted slightly.

The tilt issue also affects land compasses too.

She doesn't have a problem with navigation. She has the problem with the numbers all 180-degrees off from what she's used to while using a land navigation compass. Same issue I had until I figured out the numbers were off, and off for a purpose.

 

[Roko]

The tilt issue also affects land compasses too.

She doesn't have a problem with navigation. She has the problem with the numbers all 180-degrees off from what she's used to while using a land navigation compass. Same issue I had until I figured out the numbers were off, and off for a purpose.

If your land compass has that problem too, you need to buy a better compass

My point is that there are some POS being sold by dive gear companies which shouldn't pass as usable compasses.

Keep in mind I'm not talking about the balance of the magnet/needle for the magnetic field for the particular "zone" of the world you're in requiring the compass to be level, but rather I'm talking about asymmetrically balanced (in terms of weight) needles/wheels. A proper compass should be operate fine when very slightly off-level without north rotating to wherever the low point on the compass is.

My comment is also not a "YOU ARE DOING THIS WRONG", but rather "one more thing to watch out for when using compasses..."

 

[tracydr]

Now it's coming together. I needed a logical reason for why it seemed so different but I couldn't quite put a finger on it and it's been awhile since I did my Army training!

 

[tracydr]

Course, the times I have difficulty, the vis is so poor or it's black, black night that using obstacle markers has been impossible buts that's always a good tip to remember!

 

[boulderjohn]

It is one thing to know how a compass works. It is another thing to use it to lead dives in the real under water world.

Let's take the most basic skill: setting a course direction and then following a reciprocal heading. Once you have mastered that basic skill, can you tell how to use it to lead a dive in anything other than a straight out and straight back fashion?

For example, you are on a dive boat in Key Largo, and the DM tells you at the beginning of the dive that there are all sorts of good things to see in all directions. Feel free to explore, but be back in 50 minutes.

If you are leading a dive group that is not watching you carefully, you will lead them hither and yon, visiting sites in a seemingly random path, ending up back at the boat in 50 minutes. They will think you are a navigational genius, but you were only cleverly using the skill of reciprocals.

If you know how to do what I just described, you can figure out how to use that basic skill in a variety of other situations.

 

[tracydr]

The tilt issue also affects land compasses too.

She doesn't have a problem with navigation. She has the problem with the numbers all 180-degrees off from what she's used to while using a land navigation compass. Same issue I had until I figured out the numbers were off, and off for a purpose.

Yes, I do believe you nailed the problem. It was in a slightly different language for me!