Underwater navigation

[MXGratefulDiver]

My diving club usually sets up a navigation course in a large, relatively shallow quarry. We have plastic jugs on the surface with rope going straight down from the jug with a good, solid weight on the bottom. No extra rope because you want the jug directly over the weight and you also don't want an entanglement risk.
About 3' off the bottom is a plastic sign threaded through the rope that tells you the compass heading to the next jug in thick, large numbers (remains visible even after 8 mos underwater).

You take compass heading on to the 1st jug before going under, then try to navigate the whole course of 3-5 jugs w/o having to surface. Since you're only in 5-6m of water you can surface w/o much trouble/time/risk. As often as necessary you can surface and take a heading to the nearest jug.

It's an excellent way to make an overly familiar dive site more entertaining.

I do something similar, except I use plastic 4 x 6 cards ziptied to garden stakes. Each has a compass heading printed on it which takes you to the next card. The first card is fixed next to the buoy line we descend on. When you get to the last card it says, simply ... "Home". The goal is for the student to have used the technique I described earlier to then determine how to get back to the buoy.

This is part of my AOW class, and almost always the student's favorite dive of the class ...

... Bob (Grateful Diver)

 

[MXGratefulDiver]

Curious to know, how often is underwater navigation used on boat dives and under what scenarios would you need to use it? My only diving experience to date has been in a quarry and on boat dives where the boat comes and picks you up wherever you surface. I've been practicing some using the compass on my D6i, but it's been more to figure out how to use the compass vs. using it effectively. I figure at some point in my diving career I'm going to need to use it, or at least wished I knew how to use it.

Depends on where you're diving. In the Channel Islands, for example, boats often double-anchor ... so you're expected to come up next to the boat. If they have to come get you, they will probably be coming in a small "chase" boat that is towed behind the main boat for that purpose.

... Bob (Grateful Diver)

 

[randy88k5]

Could you expound on this please?

Not sure what they meant by that, but I have heard of problems with console mounted compasses before. I have heard where some metal pressure gauges store a small magnetic charge, and with console mounted compasses, it could affect the direction. In this case, the gauge would need to be degaussed. Then the compass should act normally.

Or that wrist mounted compasses are encouraged by DIR/GUE.

 

[cloudflint]

I've found natural navigation is invaluable, being able to look at a rock and know exactly where you are is immensely helpful. For a site i don't know its a bit trickier I generally try to talk to people who have dived on the site first and ask them how they navigate.

There is one site for instance which is just flat silt and a thin rocky reef about 10 minutes swim out. The first time I did this I took a bearing and headed out, only to miss it completely. Speaking with some guys who had dived it before i learned the trick was to head slightly to the left of the actual bearing till you hit 10 meters then swim right along the contour to hit the top of the reef.

Another site is a reef that starts from a few meters depth, but the only entrance is a few hundred meters to the side of it and again the land around the reef is all flat sand, this means its impossible to know where to exit on the way back since you can easily swim past your exit point. to navigate this site i always make a mental note of how long it takes my to swim out, then i time myself on the way in and i know when to head into land and can be fairly sure i will be near the exit point.

Ive found info like this is invaluable and is one of the reasons I go onto diving forums. Without any navigation data for a site I might as well be the first diver ever to explore the site which seems a bit counter intuitive

Also something really stupid i did with compasses, i wore one on my wrist and one on my console thinking i was clever having a backup compass in case on got smashed (It seems to happen alot around here with all the rough shore entries we do). During a dive I would often hold them next to each other to compare the bearings each one gave. It was only after a few months of doing this that I realized that no matter which way i was facing, the compasses will always line up with each other when held close since each one has a magnet in it :doh: So remember when people say to keep magnetic stuff away from your compass, compasses themselves are magnetic!

 

[FinnMom]

Originally Posted by saxplayer1004
Using those stupid compasses on the consoles is a surefire way to get lost though.
Could you expound on this please?

1) Because Your compass reads where the outer edge of your hip is going, not where your nose is going!
The hose on a console is rarely long enough to allow you to hold the computer in front of you; usually it remains a bit toward 1 hip. This makes it much more difficult to follow a designated course heading.

2) Because every time you look down at this off-center compass, it's really easy to inadvertently turn your body a little bit. => Each & every incidence causes a little deviation. I said "turn your body a little bit" but actually if you have no visual references to easily see that you've moved, even a 90 degree turn of your body is incredibly easy to do w/o realizing it.

 

[Juardis]

I have done some fairly advanced navigation. It's a guessing game at best, but you can use depth, UW landmarks like bare areas, gravel areas, grass, muck, etc. We often try and go out 100 yards, turn 45 degrees and go another 50 yards, turn 45 degrees and head back to shore. Its obviously best to do this in places you have been before. If not just surface as need be.

If doing this in a place for the first time a sneak and peek maybe necessary. IMO exact UW navigation is next to impossible unless there is awesome vis and well defined landmarks. I can usually do well on a reef for the first time, but I have also lost my bearings and had to do a sneak and peek. There is nothing wrong with going to the surface to get your bearings during a dive assuming you're diving shallow (10-50ft). I skip the SS and am back down in seconds. Granted most dives do not need much navigation to be successful.

This was the quote that prompted my question about how often and when do we need to use navigation. Re-reading a little more carefully, Ron is saying you still need some nav, just not a roadmap so to speak. I can see a navigation specialty in my near future.

 

[TSandM]

I think, on a featureless bottom with no slope, and without a line, it is quite difficult to swim an accurate circular course. But why are you diving there, again?

Almost all the dives I've ever done (with the exception of an utterly fiendish navigation dive my friend Bob puts in his AOW class, which is done with no visual references whatsoever) have involved a lot of natural navigation. As Bob says, depth contours are extremely useful. Looking at the overall site with an eye to the headings toward shore from the edges of where you intend to explore is useful, too (for example, if you are diving out of a cove). In many cases, you don't have to get back to the exact same spot you entered while under the water -- surfacing and doing a bit of surface swim is almost always an option.

 

[Peter Guy]

I confess to being somewhat "navigationally challenged" -- especially UW compass nav. I do try to keep a "mental map" as mentioned by NW GD but even that doesn't work sometimes (as Bob may recall!). It really depends on how important it is to return to a spot certain -- IF it is very important then you'd better make sure you have the tools and that your mind maintains the information necessary. And you might well be advised to add some "helpers" to make sure you are able to return -- for example, running a line from the anchor "downhill" which will give you a MUCH bigger target to hit. Or, if on a wreck, make sure you have a good "mind's eye" of the wreck's orientation so that you'll always know which way is back (or if you must, run a continuous line).

OTOH, if it doesn't matter where you come back to -- as long as you have a decent fix on where "home" might be, does it matter?

And, in the end, there is an equipment solution -- get a scooter, or better yet, a buddy with one to tow you back! (Note, a dive NWGD and I did was an absolute cluster -- no depth variation, the concrete slabs all looked the same, we were lost but came up close to the anchored boat and another diver on a scooter came and towed us back!)

 

[Malpaso]

1) Because Your compass reads where the outer edge of your hip is going, not where your nose is going!
The hose on a console is rarely long enough to allow you to hold the computer in front of you; usually it remains a bit toward 1 hip. This makes it much more difficult to follow a designated course heading.

Ok, so it's user error, not that a console compass has something mechanically wrong with it. I used a console compass on my check out dive and hit my target within a couple feet, but I've been doing map and compass on land for a few decades.

 

[Hatul]

1) Because Your compass reads where the outer edge of your hip is going, not where your nose is going!
The hose on a console is rarely long enough to allow you to hold the computer in front of you; usually it remains a bit toward 1 hip. This makes it much more difficult to follow a designated course heading.

2) Because every time you look down at this off-center compass, it's really easy to inadvertently turn your body a little bit. => Each & every incidence causes a little deviation. I said "turn your body a little bit" but actually if you have no visual references to easily see that you've moved, even a 90 degree turn of your body is incredibly easy to do w/o realizing it.

There is a point to this and when I used a console I changed to a longer hose for this reason. However once you do that it's actually more precise than the wrist mount, as it's easy to hold the wrist with the lubber line not pointing forward. With the wrist mount you have to take care the lubber line points forward.

Adam