Dive compass confusion

[TMHeimer]

The usual "bezel on North" is best, though sometimes I think I hit or move the bezel by mistake. I lost a bezel once and found that if you don't need to be too exact, you can just point the compass where you want to go and look what's at the top- ei. if it's between N & E you want to go NE, so just keep that at 12 o'clock. Or, the direction i want puts 12 o'clock just to the left of "S". You can be more exact and take a reading -ei. I want to go this way and the compass reads 130 degrees, but if your vision is less than perfect this can be difficult without some sort of prescription lenses in your mask.

 

[Hatul]

We do a lot of shore diving in poor vis and at night and I don't like fiddling with the compass a lot.

My reference direction is towards shore so before descending I set my bearing towards shore and leave it there. When swimming I look at the compass and get a mental image of where I'm going in relation to shore.

On the way back I surface when the depth is about 10 ft or so, check my exit point and set the compass to exit point and either swim out on my back or descend again and swim out by compass.

Adam

 

[David Griffith]

Start out slow. Swimming spoke patterns out and back from either the anchor or a descent line is a good way to start. You see plenty of the reef, and you never get very far from your starting point. Swimming down a bearing, and then back along the reciprocal course is a good way to get started with compass navigation.

 

[NC Wreck Diver]

I'll be the donkey and you can be the tail.

Practice in the water because on land you may walk into a wall and if you get disoriented stick with your buddy and finish the dive otherwise you may as well have stayed at home walking into walls.

Enjoy your dives and the boat will come or be there. Eventually..

Don't practice topside around any walls. I've been to your homeland. From the Twelve Apostles to Cairns. Lots of open spaces. I didn't see many 'walls' all around. I don't need to be the tail. I think you have the whole 'Donkey' part covered real well.

 

[MauiScubaSteve]

I have complete'd my basic and about to start advanced however I am going diving in Key Largo this weekend and really would like to have a idea about how to use a compass to navigate to and from the boat. I have searched through this forum for a bit and haven't found a answer to the basic question....

How do you use a underwater compass?

As you can see from the varied answers, there isn't one answer; and damn few here that will help you find your way back to the boat.

Some people seem to think the answer for your question is the same as ...how to navigate to and fro the SHORE...

How many miles wide is the SHORE and how many miles wide is the BOAT?

So far no instructors have chimed in with an answer, and SB is thick with instructors. Perhaps it's because any instructor worth a can of beans knows that for a person who got to the OP's point in life where he asks this question as his first SB post, it is likely the only way for him to really learn to use a compass is to be properly shown how to use it, in person. :kiss2:

What agency was your OW cert? If it was PADI the answer was part of the class. If you didn't "get" it in your OW class you likely need navigation training. On your first dives in Key Largo you could pay for a guide on the first charter and pre-tip the guide well to show you how, but if you didn't "get" it in OW....probably not many guide's could "teach" you how to navigate to and fro a BOAT.

Another option would be to make some of your AOW dives on your second Key Largo charter. First you need a warm up trip; are there Benwood Wreck / Statue of Jesus trips in the morning?

For the Benwood its swim around the wreck until you get back to your mooring line simple. Max depth at Jesus is probably 30 ish feet deep, maybe less; If there are no loud boat noises it is easy to surface and get a return bearing, no later than 1000 psi if you are just not sure. This experience gives you a chance to figure what you want/need out of the Nav training dive. :cool2:

Then schedule the next trip as the AOW training dives. It might be very close to the price w/ guide. Do AOW Navigation and say PPB on the second trip and your subsequent trips just might rock!

David, I liked your answer, for someone that kind of got their OW training.

As far as wreck diving goes, a novice who has not done any AOW dives yet should not be too worried about wreck diving, should he? :shocked2:

As far as compass use while Key Largo wreck diving; if "to and fro the boat" meant the Benwood, swim to a distinct bottom "non-metallic" landmark as far away from the Benwood as you can and still be able to see the Benwood, take a bearing at the Benwood, continue swimming away on the reciprocal until you can just see the "landmark" and compare that bearing to the first bearing. Adjust as needed, continue swimming away if you dare. I might have chosen a metallic "landmark" once and made a bad adjustment; the Captain was not happy at my very tardy return.

 

[Altamira]

Many of the descriptions for underwater navigation seem to stress swimming a compass heading outbound from the boat or shore and swimming the reciprocal heading inbound. Although I don't have much OW experience, I do have a lengthy military aviation background with extensive low level navigation experience so I am very familiar with using the compass to get around a navigation route. I am trying to relate what I know how to do in the air to underwater navigaion and would love to hear some techiniques for actually getting back to a fairly small target like an anchor line. When flying a low level navigation run, the heading was only one part of the navigation equation. To successfully navigate the route you also needed to apply a wind drift correction to the compass heading, fly the planned drift corrected headings at a known ground speed and for a precomputed time period for each leg based on the planned ground speed. I have been surprised that I have not heard much commentary on using compass drift corrections for current when swimming perpendicular to the current, techniques for timing the outbound and inbound legs if swimming against and then with the current, or techniques for determining distance outbound and inbound. In a no current situation, I assume that UW navigation is simply a matter of swimming a certain heading for X minutes and then the reciprocal for the same number of minutes to get back to a start point. However when diving in a current, I would think the other factors would play a much larger role if you are trying to get yourself and a buddy back to a small target such as an anchor line. If you have some good techinques, us newbies would love to hear them.
Thanks.

 

[knowone]

What can be taught to a newbie like you except where to sew your Master Navigational Instructor patch and maybe slow down..

Good post.

 

[Garrobo]

When I first started diving and the operator didn't provide a DM I made sure that I paired up with a buddy who could navigate by asking him/her if they were capable of getting us back to the boat. I still do this just in case unless I am on a really familiar reef or shipwreck dive. I am one of those people who can get lost in a one-chair barber shop.

 

[aquaregia]

It's different for reef and wreck dives.

Wreck dives you should be able to keep a picture of the boat in your head as you swim around. I take headings to some landmarks from the anchor line (and sometimes write them down), just so I don't do something like come up the port crane instead of the starboard crane.

On the reef, most of your dives will be a safety stop, so you can always pop up at 1000psi and take a heading to the boat, then pop back down and follow the heading you took. I try to make all my turns at natural markers so I don't have to count distance, only keep track of a set of landmarks and headings from them. The visibility's good enough in Key Largo that you should be able to see either the line or the boat's hull from several tens of feet away. Also, if your boat had snorkelers, you'll see them flapping about in the water. I correct for current sort of by feel, nothing scientific. If I've drifted a bit one way going out, I try to double correct going back.

Navigation in the tropics isn't particularly difficult.

 

[NC Wreck Diver]

It's different for reef and wreck dives.

Wreck dives you should be able to keep a picture of the boat in your head as you swim around. I take headings to some landmarks from the anchor line (and sometimes write them down), just so I don't do something like come up the port crane instead of the starboard crane.

Navigation in the tropics isn't particularly difficult.

Good thoughts on your post. If vis is low (off Jersey), I'll use a cross wreck line tied near the anchor line. Some DM's on our diveboats will even deploy a line off the anchor line as a guide. A lot of our wrecks are depth charged or wire dragged due to the hazzard to other ships navigation, so they are really blown up piles of wreckage. A compass and a steel wreck don't mix.