Secret of wreck location!

[Seal diver]

AMAZING TECHNOLOGY!

As all serious wreck detectives will know research is key to locating new and exciting potential wreck dives.
However, this bit of kit from StarFish Seabed Imaging System - Digital CHIRP Side Scan Sonar Systems can make a BIG difference!

I was recently able to trial a Starfish sonar off the North East coast and test how it performed - I will try to provide a brief summary below:

The kit is remarkably small! I studied Oceanography and Marine biology at Southampton University in the early 1990s and used side scan sonar there. The tow "fish" then was more like a huge naval torpedo and you needed two people (preferably buillt like shot putters!) to launch it! The image quality was inferior to the Starfish!
The Starfish side scan sonar comes in a Peli case and can be carried in one hand!


Setting it up:

It needs power and the easiest way to provide this is a 12V car (or marine) battery. In the case is an arrangement of power leads and I used the "crocodile clips" one that simply attaches to the positive and negative terminals of the battery - simple. The power lead plugs into the "gizmo" box (about the size of paperback book) and an LED light confirms you have power to activate the sonar fish.

The "fish" itself (ie the thing you tow) is about a foot long and remarkably the power cable and feedback cable doubles as the towing cable! It's about 20m long and a very strong plastic coated cable. One end is fixed to the fish whilst the other end attaches to the "gizmo" box with a simple connection. To secure the cable when towing it can easily be wrapped a couple of times around a large round cleat or similar. (avoiding any tight turns in the cable) - or you can use a soft rope (eg climbing rope) or webbing and tie that off to the boat and around the cable... I did both as I didn't want to risk losing it!!


The only other thing needed is a laptop computer.
This sounds a pain but in fact was very easy to set up (the software can be downloaded from Software Downloads - StarFish Seabed Imaging System - Side Scan Sonar Towfish) and is very straight forward.

A USB lead from the "Gizmo" box plugs into the laptop and off you go it's scanning the seabed as soon as you lower the fish into the water over the back of the boat. (Wait till the boat is moving slowly forward at 1-3knts)


The images provided detail 50m either side of the boat at a depth of 25-30m.
Metal shows up white (as it reflects the sonar waves) and different densities give different shades of colour. Objects proud of the seabed leave a shadow which can also be seen. (check images on gallery here>> StarFish Gallery - Side Scan Sonar Seabed Image GalleryWith a bit of practice the images can be understood quite quickly.

Only downside for me was the battery life of the laptop which curtailed the adventure!

Obviously with a laptop and "Gizmo" box you want to search on a dry day and preferably with calm conditions.

Images are divided into port (left of boat) and starboard (right of boat) as it moves forward - the image below shows wreckage of the Somali to the port side of the boat. (defined white edged shapes)


I used the Starfish over the SS Somali where it helped pin point the location where the solid brass fire extinguishers are located(!) and it provided some very interesting images (despite pretty windy weather and surface swell).

In summary there are many undiscovered wrecks out there and this bit of kit puts the latest side scan sonar technology into the budget of many clubs (the kit could also be hired for a specific project/ expedition).

Safe diving,
Ben "Seal diver"

YouTube - bburville's Channel

[John63]

Oh bu$$er. I want one. Scooter or Starfish, scooter or starfish.....

[Scuttler]

And a bargain at £1699!

[SoggyFox]

I was looking at these and you may just have tipped the balance, looks like a great piece of kit. Even a club could afford one and it would enable divers to get a real sense of what they are diving on.

[hugoboss]

This is a very tempting piece of kit, im in love with it already, its now on my list of wants and its relegated the jetski to second place..

[stevechesh]

I'd be interested in seeing the results of real images of deep wrecks in the 50 metre + range if anyone has any. Can't see the images on my phone but is wreck position lat and long displayed on the image?

[neilh]

Interesting stuff Ben - any chance of a larger sample image from the Somali to get a better feel for how it performs?

Also is it really limited to 30m? Would be a shame if it is

[hugoboss]

Can't see the images on my phone but is wreck position lat and long displayed on the image?

theres an option to purchase a GPS positioning addon for it

[hugoboss]

Due to battery life on laptops, what do you guys reckon to wiring up a cigarette lighter thingy (like you have in cars) to the boat and then run the lappy of a mobile charger (you can buy em for car fag lighters), im not very savvy with electrickery but would it work in this instance? so you could use the Starfish for longer

[Seal diver]

As far as I am aware the Starfish unit itself is not suitable for towing deeper than 30m BUT the images can be obtained from depths far deeper

To put this in perspective - we were towing the Starfish at a maximum depth of 10m and the seabed was at 40m in some areas - we could very clearly see the seabed!

When we went over the Somali (lying at 30m max on the day) the Starfish was at about 7-10m maximum depth.

I don't know what the maximum image depth would be but I would hazard an educated guess that (given the fact it works off sonar waves which travel very fast in water) you could get decent images from depths far deeper than even the "ninja techies" amongst you dive!

Safe diving,
Ben "Seal diver"
YouTube - bburville's Channel