PSDarchives.sonar

Sonar

8-29-02

At the FD where I work, we were recently given 5 new inflatables to train with that are to replace some current boats in use. We don't dive yet, (the cops do), but I was able to convince someone up the chain of command to look into a sonar unit.

The problem is how to mount up front to get a clear picture. They are currently mounted in the back on the transom, but we pick up a llot of churned water. Has anyone had any luck with a temporary mount, preferably a pole, on an inflatable.

Thanks,

Digger Treinish

MFD Dive Rescue

8-29-02

You might try mounting the transducer on a short pipe and clamp it to the stern of the rubber duck .

If you run the boat backwards, you will not pick up the bubbles in the water.

we do it this way and it appears to work.

grumpie

8-29-02

We've toyed around with a suction-cup mount to the side of the inflatable
just below the water line. It's not the most hydro-dynamic configuration,
but the clarity was far better than with the churn at the back. It works
for slow-speed searches--any faster than 1.5kts or so and the suction cup
comes off.

Jeff Tibbitts
Davis County Sheriff's SAR

8-31-02

Thanks for the info. I dont think going backwards in it is a real option, as much of our searches are in a good size river, with considerable current. I have explained that option, though, to the troops, as we do have some larger lakes and such.

Jeff, is this a suction cup that actually sticks to the rubber(?) of the boat? I like this idea, provided it doesnt rip off too easy. Did you make it yourself? I also like the idea of slowing down the FFs that are going to use it, as it has been hard to keep the pace down for a nice, done-right search. They are too used to acting with speed.

Thanks again,

Digger

8-31-02

AMEN on slowing everyone down for a "done-right" search!

Also a reminder SONAR should be used with caution when divers are in the water. The normal low powered hand held or fish-finder types are usually not a problem. The high power SONARs can cause burns and serious bodily harm
(including death) if divers are in close proximity. Check the USN Dive manual for details. Like I said the normal search SONARs we are likely to use should not be of concern but how many of us dive in harbors or ports where ocean going ships/military ships are moored? Their SONAR's can cause injury!

Just something else to think/talk about,

Safe Diving!

Officer Ronny Phillips
Dive Master
Galveston (TX) Police Department
Marine/Dive Unit

8-31-02

We also have a side scan sonar in are stock , that we use. We did some work on the mississppi a month ago, it worked

ok. you were able to see in three barges wide and even see the cracks between them.

grumpy

8-31-02

do you have other references available? "Sport" sonar does not give any warnings of significance. Do you know of any web sites that may address this issue.
You bring up an interesting point and one that should be investigated further.
Chuck

8-31-02

I only have seen it mentioned in the Navy dive Manual. It was also covered when we were trained in Hull Searches. I'm sure commercial dive courses would cover it also.

It is something that is not in the normal real, of PSD, but should be for Teams that dive in harbors around ocean going / military vessels.

Officer Ronny Phillips
Dive Master
Galveston (TX) Police Department
Marine/Dive Unit

8-31-02

Ref: Sonars and Divers

A. USN Manual

B. Canadian Forces Diving Manual

1. Hand held sonars (2A) and boat fish finders along with many towed array sonars have specific paths they shoot, and given thier size generally do not pose any hazards to divers in the area or operating them. However when conducting Explosive Ordnance Reconnaissance , or operating in an area where either Influence Ordnance or IED's are suspected (Improvised Explosive Devices), this is not prudent.

2. The person(s) placing these items may have taken into consideration the botom cartogarphy and assumed devices such as these are being utilized, hence diver or boat operated, and they may be set to detonate or "wake up" when these devices "ping" on them.

3. As for larger ship borne sonars they too can be path directed or wide band search set, when on full, or long range, they will kill a diver within 100 yards, up to 200 yards or even 300 on some of the larger models, will bring a diver to the surface, ruptured ears drums, naseau, charged fillings (teeth).

4. In port however they are not set to "send" as much as to recieve, and the power setting is generally lower, however, our procedures are to ensure no sonars are operating, if they are, a solid jetty (wharf) or a bend in the harbour, (around the corner) will suffice as a barrier to this problem. The diver working in the water in this instance however will hear the sonar and may complain of a headache depending upon the strength of the signal(band)

5. LGS presently teaches teams how to conduct Explosive Ordnance Searches, and Explosive Ordnance Recognition, I should know I am one of the instructors for that course. Further information can be obtained by contacting LGS. This course also teaches Ships hull searches, jetty searches, bottom searches, Tactile searches of Ordnance and basic recoginiton, an safety procedures. This is all on power point presentation.

6. Hope that cleared up a few questions.

Cam Jones

Sgt Winnipeg Police Service

Chief Petty Officer Second Class

Canadian Armed Forces Naval Reserve Port Inspection Diver, National Dive Training Chief.

8-31-02

An interesting article was near the top of the list in a quick Google
search on this subject:

http://www.nrdc.org/wildlife/marine/nlfa.asp

"According to the Navy's study, scientists briefly exposed a 32-year-old
Navy diver to LFA
sonar at a level of 160 decibels -- a fraction of the intensity at
which the LFA system is
designed to operate. After 12 minutes, the diver experienced severe
symptoms, including
dizziness and drowsiness. After being hospitalized, he relapsed,
suffering memory
dysfunction and seizure. Two years later he was being treated with
anti-depressant and
anti-seizure medications."

No mention was made about how this might apply to the relationship
between "normal" "high power" ship sonar (whatever that is), and divers.

Gene

9-1-02

It’s a suction cup that came with the GPS/Sonar combo (a Garmin). With a well-inflated boat, it actually sticks to the rubber better than to the wooden transom. We don’t have the $$ to purchase side-scan, but this works well for now.

Jeff

Lifeguard Systems, Inc. Box 594 Shokan, NY 12481

Phone: 845-657-5544

Fax: 845-657-5549