Practical Navigation Techniques

[Davwardo]

Hello everyone. Can anyone help me out with some advise on basic navigation techniques. I have approx 30 dives ( all warm water, fairly good viz ) but have always followed a dive master.

I would like to start diving independently of a dive guide and would like to ask people for some practical advice on navigation. I've recently bought a compass and have been practicing using it ( strangely, I've been getting some wierd looks as I practice squares in my local central London park ;-) ).

I'm planning on starting diving in the UK this year and am going to Cayman Brac in March. Obviously, very different dive environments! I'd like to practice in Caymans for the UK diving!

So:

a) What do people generally do to get themselves back to the boat?! Do you ( like the books say ) swim squares, triangles etc or mainly use natural navigation ( or both )?

b) What do you do if you know you want to head off in a particlar direction to start with but would like to then explore after that?

c) How does viz effect choice of navigation techniques?

Cheers

Davwardo

 

[Drew Sailbum]

Last one first. Natural navigation techniques are easier, IMHO, in conditions with better visibility. Around Grand Cayman this usually involves following bottom contours (edge of wall drop off, coral fingers, etc...)

What technique you use depends, in part, on how much information you have about the site.

 

[Amberjack]

Hi Davwardo -

I asked a similar question and got some great, very useful replies:
http://www.scubaboard.com/showthread.php?t=127763. Check out in particular the very useful link to yet another discussion posted by Diver0001.

I'm interested to see what other advice crops up here!

 

[Davwardo]

Thanks Amberjack - some good tips there!

 

[kjundvr]

a) What do people generally do to get themselves back to the boat?! Do you ( like the books say ) swim squares, triangles etc or mainly use natural navigation ( or both )?

b) What do you do if you know you want to head off in a particlar direction to start with but would like to then explore after that?

I usually start out my dive at the bottom of the anchor from there I pick a direction (likely have already chosen this from the surface with buddy) and general swim in that general direction. I usually break up the straight line by zig zaging across my chosen path by about 8-10m either side of the chosen path. Using this i know the general direction of the boat and so can get close to it.

c) How does viz effect choice of navigation techniques?

Most of my diving is low viz (<3m) I use the same as above when diving from a boat. I just usually can't find the anchor line again. So I attempt to get as close to the boat as possible then surface. Sometimes I am right next to it and others I am not. If I am doing a deep boat dive and the anchor would be useful for doing my ascent I just run a compass heading less confusing that doing shapes (no math underwater or dealing with slates) and its just 180 to get back to the boat.
If in very good vis such as found in the Caymans I usually can look and see the anchor line or the boat. As with every boat dive I keep track of the general direction of the boat and in good vis I know exactly what direction to look or swim to find the boat.

Also when close to shore sand ripples are my best friend. Just keep in mind the shape of the beach because in some areas such as where a peninsula just out the waves have a tendency to bend and therefore the ripples are not always perpendicular to the beach.

 

[Pyrofish]

I used a reel attached to the anchor line one time. We were searching for something though and used the anchor line as a pivot point to base our search on. Unfortunately, I'm not profficient at using a reel yet and it turned into a cluster... We found what we were looking for though, so it worked out.

 

[MXGratefulDiver]

A compass is just one of the tools you can use for navigation. In my AOW class I teach a technique called "mental mapping". It uses four variables ... depth, distance, direction, and time ... to help you build a picture in your head of where you've been, so you always have a general idea of where your starting point is relative to where you are now.

Our local conditions are rarely good enough to enable a diver to see more than 15-20 feet, so finding an upline can be challenging ... but I've found that my students can usually get themselves back to an upline within a few feet using the technique. It requires only the usual diving tools ... compass, bottom timer, and an aware mind.

.... Bob (Grateful Diver)

 

[dkktsunami]

In Cayman the viz is extraordinary (100+ feet). Most of your dives will likely be along a wall. When you enter water drop to the bottom which will likely be 20' - 40'. Take note of how deep the water is where the boat is anchored. Also look around at the marine life and topography - take note of any unusual or remarkable features that you can recognize on return. You will likely be following wall into a slight current and this will be the deepest part of your dive. When you approach 1500 lbs. swim up to the top of the wall to a point that is near your starting depth. Also notice how much time this has taken. Your return trip will go quicker so take this into account. Work your way back toward the boat, enjoying the sights, and when you are close to where you think the boat will be, begin looking around and up. Look for bubbles of other divers, the boat on the surface, the anchor line, the shadow of the boat on the bottom, the natural structure you noticed when you first descended etc. It's pretty easy in Cayman. Have fun.

 

[Davwardo]

Thanks for all the advice so far guys - good stuff!

 

[double80s]

Like others said, take note of your depth when you drop down. From there, I generally try to keep the navigation simple. Using my compass, I make note of the time I travel in a particular direction, and factor in things like time spend stoping to look at objects. If I change direction, I make a mental note again of my time from my turn pioint and the direction. If I choose to continue in a square it is pretty straight forward to navigate or if I want to return in the same direction, I just need to reverse my heading and follow the same time pattern. You can use your slate or wetnotes to record changes in headings, depth, and time, but after a few dives you'll build the confidence needed.