Why north at 180 degrees?
- Thread starter SelkieDVM
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This has got to be a joke, right?
Your profile has you listed as DM; It would be interesting to see a list of your training locations and instructors!
Your profile has you listed as DM; It would be interesting to see a list of your training locations and instructors!
SelkieDVM:
It doesn't. You're reading it incorrectly.
elan
Contributor
Looks like a joke
Whether this is a real post or not, I will respond, because that's what I asked my OW instructor when I got certified and he couldn't respond. This question has also come up in several classes that I have DMed.
If you're familiar with land navigation as with hiking and camping or in my case the Army, you may be used to compasses that have the needle mounted on a disk that has the various degree headings.
On this type of scuba compass, you do not read the degree numbers on the disk from the top. The numbers on the disk are for reading only through the window on the back. So, if you're headed towards 0 degrees, the disk will read 180 on the top, but 0 from the back. In other words, all the numbers read from above at the front will be opposite from those read from the back.
You use the top part of the compass by setting your heading with the numbers on the bezel and turning the direction you are facing until the 0 mark lines up with the North mark not the 0 on the disk.
To simplify things, I just tell the students to look through the back window and forget using the top degree markings until they take AOW.
If you're familiar with land navigation as with hiking and camping or in my case the Army, you may be used to compasses that have the needle mounted on a disk that has the various degree headings.
On this type of scuba compass, you do not read the degree numbers on the disk from the top. The numbers on the disk are for reading only through the window on the back. So, if you're headed towards 0 degrees, the disk will read 180 on the top, but 0 from the back. In other words, all the numbers read from above at the front will be opposite from those read from the back.
You use the top part of the compass by setting your heading with the numbers on the bezel and turning the direction you are facing until the 0 mark lines up with the North mark not the 0 on the disk.
To simplify things, I just tell the students to look through the back window and forget using the top degree markings until they take AOW.
When you're looking down at the compass, you can set the rotating bezel for navigation and reciprocal headings.
When you're looking through the window on the side of the compass, your true heading is displayed, because it's showing the side that is 180* off of your direction of travel.
Example, when your compass is pointing North, if you look in the window, you'll see a direction of 0*. When you turn and face South and look through the window, you'll see the 180* mark displayed.
PanamaMike
Registered
Yes, dive compass are marked odd compared to those for hiking, sailing or
anything else. It deals with whether it's a direct or indirect reading compass.
See, e.g., SCUBA
--Mike
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Themons,you've just beaten me to it.
The difference comes from the landbased and the nautical compasses.(we use nautical)
Just take a look at any compass on the bridge of any ship.(just google for it)and you'll see how they are used. The army is a good example for the landbased compasses(so are boyscouts)
I've seen an instructor sending divers 180 degrees offcourse just because he learned to navigate in the army.Just use the window at the back and you'll be fine.
The difference comes from the landbased and the nautical compasses.(we use nautical)
Just take a look at any compass on the bridge of any ship.(just google for it)and you'll see how they are used. The army is a good example for the landbased compasses(so are boyscouts)
I've seen an instructor sending divers 180 degrees offcourse just because he learned to navigate in the army.Just use the window at the back and you'll be fine.
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