Dive Compass Cardinal Direction Markings Off?

[lowviz]

...//... I was used to the land compass and when I got my underwater compass, I was like, "WTF, over?" Then somebody explained to me and then I'm good to go. ...//...

Yes, exactly. The problem is that an underwater compass is trying to be both at the same time. This violates an important principle:

"Aesthetic and minimalist design: Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility."

So you can't see N/S/E/W in the window? Why? Because you don't use them. They are there because everybody knows that N/S/E/W just has to be on a compass or why buy it?

Here is the problem, I want to go West. So I look at the top, remember the number positioned next to the W, then orient myself until that number shows up in the window. Now I'm swimming East...

---------- Post added August 29th, 2014 at 03:46 PM ----------

Nobody is going to jump all over the fact that all you have to do is rotate the bezel and everything works fine if you look at the CORRECT set of numbers? The ambiguity is what annoys me.

 

[Bob DBF]

Yes, exactly. The problem is that an underwater compass is trying to be both at the same time.

Or is it the user is trying to make it something it is not.

I did not have to read the instructions on my UW compass because I had used marine compasses and knew what they were trying to do. I guess the wrist compass is not large enough to accommodate two sets of azimuth markings, as a number of the larger marine compasses use, and leaves off the one for reading directly above (except for the needle and E W markings) as it is not needed the way this compass is to be used. If the bezel and needle painted on the card were not used, they could have closed the top, as you see on the auto and some marine compasses, and not had the issue.




Bob
-------------------------------------------
Always use the right tool for the job. A hammer is the right tool for any job. Anything can be used as a hammer.

 

[Subcooled]

There are two types of compasses:

1) compasses for orienteering (turn the bezel to record a bearing from a map, keep it stored, keep the north dial between the marker lines and follow the arrow on the compas bottom plate)
Example: http://www.suunto.com/en-GB/Products/Compasses/Suunto-A-10/Suunto-A-10-CM/

2) sighting compasses that tell you in which direction you are looking (these come either with a sighting window or a mirror)
Example: http://www.bapequipmentstore.com/images/products/large_650_kb14.jpg (note the black side window)

Sighting compasses are much more usefull under water as you probably won't be relying on a map but instead want to dive in a chosen direction (out/in/along the shore/...). You have a known bearing in degrees. In order to achieve this you would ideally look through the side window and locate a landmark (or two in a row) behind the compass. Then dive in that direction keeping the landmarks in line. Repeat. This procedure is not easy if you look at the compass from above. This explains the side window and why diving compasses tend to be sighting compasses. Accuracy is also increased (and parallax reduced) as the compass is held farther away. Sometimes however, a rough bearing is all that is needed. In these cases it would be easier to just quickly look down. Hope this explains the numbering on the disk.

ps. Also note that there probably are separate batches of compasses calibrated for northern/southers hemisphere and the equator ... because of the tilt of earths magnetic field. In the north the magnetic field goes down. Not so on the equator.

 

[lemke]

I never noticed the difference, but then again, I never had a land and UW compass side by side. Any heading you take is just a number, just keep it consistent on your dive. Ergonomically speaking, doesn't it make sense that the bearing numbers that are "right side up" should be the ones you use for your heading?

 

[tekful]

So.... my wife just pointed out something that I never noticed for some reason. Suunto marked E at 270 degrees, W at 090, North at 180, and South at 000. See this image View attachment 192176 Looking online it seems a lot of dive compasses are marked this way. I know non-dive compasses are marked "correctly" such as this View attachment 192177. Are we missing something?


Edit: Ok we found the explanation. I still think it backwards as all heck but I understand the reasoning now at least.

The small little window in dive compass is for back bearing it'd always 180.

I agree with points both of lowviz and divemasterdenis have made. I never used the cardinal directions, just headings so never got me lost. I do think it is confusing, but only if divers are doing two things 1) navigating the compass held under them vs in front and using the sighting window 2) relying on cardinal directions for navigation. Considering I was only trained to hold it underneath me that seems easy enough, I can also see a visitor to a new area getting directions in cardinal directions. I just now know that I need to automatically use the appropriate heading instead of cardinal direction.

It’s not a big issue and really only takes an instructor mentioning it during OW/AOW, but mine were so focused on how to do the reciprocal and swim cycles they forgot to mention it and thus this forum post.

That would make it even worse, as you couldn't tell which way the compass is marked. When you're facing north with any other compass, the zero would be at the top, but on a dive compass it's at the bottom. It took me a while to clue in on that as well... without cardinal markings, you wouldn't even know!

 

[cocoajoe]

Just explain to people; expert and novice alike, how the underwater compass display is different than land compass display. It ain't rocket science.

I was used to the land compass and when I got my underwater compass, I was like, "WTF, over?" Then somebody explained to me and then I'm good to go.

Once again, it ain't rocket science and it ain't a big deal. I use my lensatic compass for navigation on land just fine nowadays, and when I go underwater, the Suunto does it for me. No confusion, no fuss, no muss.

Exactly. Window is reverse heading on a simple to and from dive or else get out your slate. Perhaps some practice?

 

[lowviz]

I swore off my rant as nobody really cares. Anyone who knows how to use an indirect reading compass thinks this whole thread is stupid and anyone who doesn't couldn't be bothered to do a read through.

Or is it the user is trying to make it something it is not.

See, I think that this really is the problem. Hand one to an un-experienced diver and he/she thinks terrestrial compass. Line up the needle with North and all is good. What's with this rotating bezel"? And a side window?

I never noticed the difference, but then again, I never had a land and UW compass side by side. Any heading you take is just a number, just keep it consistent on your dive. Ergonomically speaking, doesn't it make sense that the bearing numbers that are "right side up" should be the ones you use for your heading?

So I'm tied-in to a scattered wreck and the captain says head East to see all the cool sights. OK. I have East on my compass tied to a number and I have a ring of numbers that I can set anywhere. Which number do I pick?

Exactly. Window is reverse heading on a simple to and from dive or else get out your slate. Perhaps some practice?

OH, so you use the top for outbound and the window for inbound?

Yes, indirect reading compasses are designed to be immediately intuitive.

NOW I'll give you guys some peace along with my apologies. I'm out of this...

 

[redacted]

You know, it is just not that hard. The arrow points north. Figure the rest out.

 

[lemke]

Uh, I would head East, or a 90 degree bearing... which are magically always the same.

 

[DukeAMO]

I came from a background of quite a bit of orienteering, and also had a WTF moment with the underwater compass.
Underwater navigation is significantly more difficult than on land, IMHO, because of task loading, limited visibility, and navigating in 3 dimensions instead of 2. Plus you usually don't have a nice map in hand underwater.
That'll be $.02.