OW scootering with a surface marker buoy

Hi all

We're helping with a reef mapping project which is published on Wikitravel and titled "Diving the Cape Peninsula and False Bay"

I'd post the URL but SB won't let me as I am a bit of a noob here.

The other divers are swimming with surface markers fitted with GPS but we are using Mako scooters. Our GPS tracks are not as accurate a the swimmers' tracks but its usable.

My specific interest is not so much mapping exsisting reefs and wrecks but finding new ones and we've had some great success with that so far.

I've searched all over for quite some time but aside from a few posts on the Gavin Scooters list about which float from Riffe they use I have not found much about procedures for towing a surface marker with a scooter.

Obviously attaching the line to your person is not a good idea. Holding the reel in your left or right hand is possible (we scooter with the right hand) and I see that there's a Kent Tooling reel purpose made for scootering which might work well. Its kinda like a reel with a goodman handle attached.

What has worked quite nicely for us so far is a ratchet reel attached to the top of the scooter body. I'm using a bracket to attach the reel which I had made and was originally intended as a camera mount. Whats great about attaching the reel to the scooter is that:

- the line is in front of you where you can watch it and make sure that you avoid entanglement
- you don't have to hold onto the reel, so it frees up your hands
- if you keep the line under tension it stays well clear or the prop
- you can retrieve line with one hand because you don't have to hold onto the reel and wind with the other hand

We've "calibrated" the line with a permanent marker pen so you can judge the angle of the line (and therefore the distance) between the diver and the GPS on the surface. If you know your depth and how much line is reeled out it makes things simpler. Bear in mind that the viz here is often not so great. Last Sunday we scootered in viz which was only 5-6 meters.

The closer to 90 degrees the angle of the line, the more accurate the mapping and by implication there is less line in the water.

Just curious if anybody has any advice or tips or comments. Maybe somebody here has done something similar?

rgds
monty

Just wondering what the depth of the reef is and whether or not the scooter equipped diver could drop small weighted plumb lines to mark control points for the survey? Certainly would beat dragging along line. In short - start at one control marker, drive to the next "best" point and drop a small weight with surface bobber....move on drop another and then have someone on kayak (with GPS) mark set points and pick up the floats afterwards? Line freely floating in water becomes a big drag.

Just a thought as I couldn't quite grasp the intended procedure using a forward-mounted, ratcheted spool of line.


X

Mr.X:

Just wondering what the depth of the reef is and whether or not the scooter equipped diver could drop small weighted plumb lines to mark control points for the survey? Certainly would beat dragging along line. In short - start at one control marker, drive to the next "best" point and drop a small weight with surface bobber....move on drop another and then have someone on kayak (with GPS) mark set points and pick up the floats afterwards? Line freely floating in water becomes a big drag.

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Thanks for your reply.

The reefs we intend to map are 50 meters at the deepest. For now I'll stick to shallower than 30 meters/100 feet for longer dive times and mapping larger areas.

We're mapping entire reefs, not just points on the reef so dropping markers will not help with what we are trying to do.

We are able to mark points of interest by noting the dive time and correlating it to the GPS track log. (The dive computer's time is synchronised to the GPS, and the dive computer's profile is also downloaded)

And when looking for new reefs and wrecks the ability to record tracks means that you can ask the boat to drop you in an area that you have not been before.

Mr.X:

Just a thought as I couldn't quite grasp the intended procedure using a forward-mounted, ratcheted spool of line.

X

Click to expand...

Mounting the reel means hands free operation most of the time. On all dives you need hands to to let line out on descent and retreive line on the ascent, but the rest of the time its hands free unless you want to change depth and/or line tension.

If we are scootering to map a contour we don't need to let out or retrieve line because we are scootering at a constant depth.

If we are exploring or mapping the outer edge of a reef the depth may vary throughout the dive. Using a ratchet reel means that you don't have to fiddle with locking screws when we make adjustments to depth and/or line tension.

rgds
monty

Monty.

How do you calculate the layback of the float? Your accuracy would be in doubt if you ask me. A simple sidescan of the reef would yeild accurate results in hours as opposed to days?

HowardE:

Monty.

How do you calculate the layback of the float? Your accuracy would be in doubt if you ask me.

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Trigonometry - I know how deep I am and the line is calibtrated.

Having said that we are not looking for high accuracy.

What we have done so far is way better than what there was before - which is nothing.

If you have a look at the travel wiki you will see that this is no Mickey Mouse project - it is the single most detailed source of information on our country's dive sites that we know of.

HowardE:

A simple sidescan of the reef would yeild accurate results in hours as opposed to days?

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If we had access to and money for side scan we would use it. This entire project is self funded and people contribute as volunteers. I don't even get a single free boat dive out of it, and I am quite happy with these terms.

The travel wiki already has over a hunderd sites listed with maps, details on access to the sites, experience required, what you can expect to see, etc.

rgds
monty

I'd be curious to see the wiki, as I do surveys with sidescan and other devices. I also have rigged a similar GPS system, but only for marking individual waypoints, and not necessarily to record tracks, and make charts. You can post the link without the .com and www part now. SB doesn't allow users to post weblinks before they have 10 posts, as an anti-spam measure.

Attach the reel (or any line) to the body of the scooter and it will soon become a contest of "how much line can I inhale into the prop". Regardless of your watchfulness.

Don't ask me how I know this.


All the best, James

Why do you need to operate the reel while scootering?

I put a loop of monofilament or some other study ring on the rear of the scooter fairing. Have about a 6 foot piece of thin cord or rope and run it though some polyethelyne hose (pneumatic air tool hose works great too.

Use the section of "hose rope" between the scooter and the reel. The rope/hose will go back beneath you and behind you, between your legs. At the other one of the hose, clip your reel off.

The whole idea is to make the line "stiff" anywhere near the scooter, so it is very unlikley to get sucked into or entangled in anything, especially the props.

Scootering while towing a float is not unusual.

HowardE:

I'd be curious to see the wiki, as I do surveys with sidescan and other devices. I also have rigged a similar GPS system, but only for marking individual waypoints, and not necessarily to record tracks, and make charts. You can post the link without the .com and www part now. SB doesn't allow users to post weblinks before they have 10 posts, as an anti-spam measure.

Click to expand...

Hi Howard

Here you go - it is a .org domain name

???.wikitravel.???/en/Diving_the_Cape_Peninsula_and_False_Bay

rgds
monty

I'm trying to see where your survey results are used? Are you making maps, or just posting GPS #'s for dive sites.

The wiki is very comprehensive. Nice work on that btw.

While I'm still not sure what you're using your towed data/survey for...

Here is a Bathymetric map we made using Grass, and data from our magnetometer.

Is this something like what you want to do?