Surface Sonar

[nikezz]

Hi,
Anyone have any experience with surface sonar? I am looking for a sonar that can detect and identify objects floating on the surface of the water. Range 1-50m. It must be able to be mounted on a boat no more than 12 m. I am not looking for fish. Thanks.

[Submarine Tom]

That's good you're not looking for fish on the surface of the water because they don't float there. What you are looking for is called radar. Its readily available for 12 m boats with 1 - 50m range.

What is it you are looking for?

-Tom

[michael pierzga]

Its already developed. Ive seen it advertised at boat shows. Dont know anything about is, I believe it was French technology. Try googling ......it was being developed for the ocean racing single handers. This was maybe two years ago when first read about it. The developer of the technology was connected to the French defense aerospace industry

[CDK]

Originally Posted by nikezz

Hi,
Anyone have any experience with surface sonar? I am looking for a sonar that can detect and identify objects floating on the surface of the water. Range 1-50m. It must be able to be mounted on a boat no more than 12 m. I am not looking for fish. Thanks.

Take an ordinary depth sounder with a transom mounted sensor that you rotate almost 90 degrees, so it scans the surface. You need to experiment with the proper angle because you get a lot of air-water boundary echo if you tilt it too high.
Once you're satisfied, mount the transducer near the bow of your boat, unless you're only interested in stuff the fell overboard.

[tom28571]

Originally Posted by CDK

Take an ordinary depth sounder with a transom mounted sensor that you rotate almost 90 degrees, so it scans the surface. You need to experiment with the proper angle because you get a lot of air-water boundary echo if you tilt it too high.
Once you're satisfied, mount the transducer near the bow of your boat, unless you're only interested in stuff the fell overboard.

Are you sure this will work? I'm also fairly certain he is talking about RADAR. If not, no SONAR will do what he asks.

[keysdisease]

Forward or side looking sonar:

http://www.interphase-tech.com/

http://www.humminbird.com/leading_in...e-imaging.aspx

I have heard mixed reviews regarding how well these work for hard targets just below the surface.

Steve

[CDK]

Yes, it will.
The object has to be partially submerged of course, a piece of Styrofoam will not be detected. Also, in choppy water, lots of small random echos appear, especially when the transducer is pointed to far upward.

The transducers I am familiar with have a wide or narrow detection cone, so the field at any distance is always a circle. For scanning the surface a transducer with an elliptical cone would be better, but I don't know if they exist.
I once experimented with a horizontal transducer and found it very helpful to measure the distance to the shore in the dark. On deep water it also shows the floating markers of fishing nets, sometimes even the ropes.

[TeddyDiver]

Originally Posted by CDK

For scanning the surface a transducer with an elliptical cone would be better, but I don't know if they exist..

Yes they do.. Sidescanning sonars have like that very flat elliptical area..

[JosephT]

Any good side scanning sonar will do. Keep in mind you will only see the submerged portion of the object. For better distance use a powerful, narrow sonar (e.g. 5 or 10 degree max). I built a prototype several years ago that would shoot 500ft+. Results are better on calm water. If it's too choppy you'll have to aim the sonar cone slightly lower so you don't pick up cavitation/noise caused by waves.

I used this sonar to sneak up on schools of fish and locate those hiding under shoreline structures.

Locating anything above the surface would require radar.

[Submarine Tom]

And what is it we're looking for in this case nikezz?

-Tom

[gonzo]

A sonar will only work on surface objects if the water is perfectly flat. Otherwise, the face of the first wave will give a reflection. RADAR is the best option, but will get noise from waves too.

[nikezz]

Originally Posted by tom28571

Are you sure this will work? I'm also fairly certain he is talking about RADAR. If not, no SONAR will do what he asks.

I know about radar. It is not what I am looking for.

The best analogy I can think of is an iceberg. I am not looking for the tiny tip, I am looking for the hidden section located under the water. However, said iceberg is not vertically long on length nor is it huge. It's just under the surface of the water. Alternatively, think of broken debris that can float on the surface with almost nothing sticking out. Small above water, slightly bigger under water.

@michael pierzga Thanks for the tip.
@gonzo yep that was the problem with the radar. That's why I'm not aiming for that. I was hoping to find sonar that could do the job as well.
@Joseph T Needs to be JUST below the surface, not further down. Thanks for the idea. I like the side scanning sonar. What I've seen so far are SS sonar that tend to be used for deep depths, for high resolution images. However, I haven't come across one that looks closely at the surface. Do you have one you can recommend? Does your prototype work just under surfaces?
@ CDK Not sure if that idea would work, sorry if I sound harsh. However, thank you for the idea.
@ Tom Posted it above
@ Keys Thanks. Those were the only 2 I found as well, but neither seem to consider JUST under the surface.

[Submarine Tom]

Why an analogy, just say what you're looking for, it will be a lot easier to help you.

-Tom

[nikezz]

Originally Posted by Submarine Tom

Why an analogy, just say what you're looking for, it will be a lot easier to help you.

-Tom

Can I not reveal it, please? Thanks.

[Doug Lord]

One area that will require the ability to detect objects at to or close to the surface is high speed ocean sailing. And the preeminent Team associated with development in this area is Team Hydroptere. I'm not sure how forthcoming they would be but it might be worth a shot. Since round the world sailing on hydrofoils depends on not hitting anything I know they are working on this problem.