I figured I would start a thread on this since there is so much bickering between Tim and Padilla.. Yes, Tim used this device in the search for Caylee... Now, most share the success of the sonar devise as yes it is a wonderful useful device. But, there is more to it, it's not all cut and dry.... Mistakes can be made, body's sometimes are not found, items that look like trash and boulder will show up, what is beneath or in them will not for the most part. So, here is the post and all that can share creditable information please do... There is always a positive and negative to all of today's technology. I see why Padilla wants to dive the river and other areas, I see his reason and hope that all will understand why by educating ourselves. The media does not report everything, and people tend to paint a certain picture of how things are being done....
While doing a bit of research this technique is very useful in finding drowning victims and other. I also have heard and read that at times "things can be missed" and that is why a good dive team and a thorough search should be conducted. At times they see a boulder or other objects, but "without going into the water and pulling the objects out there is no way knowing for sure what is in the package or other"
I had followed the Peterson case and I did remember reading about them using side scan sonar and also read where at times you can miss things in the water.
In The Search for Laci Peterson
UW: What do you look for in the data as telltale signs that you might have found a body? What other
objects are most often mistaken for bodies with sonar searches?
GR: Accidental drowning victims are very distinctive and generally quite easy to identify. We can usually
see arms, legs, and torso. Homicide victims, however, depending upon how they may be "packaged," are a bit more difficult to identify. Quite often they will not display arms or legs, and may be found lying in a variety of positions because of objects attached to them.Also, in homicide cases, it is very critical to
have an idea of what you are looking for, otherwise, nearly every "out-of-place" object is a potential target of interest.In another homicide case, an ROV was sent down to recover the victim.
The object appeared to be a large boulder in the video from the vehicle, so the ROV operator moved on. After awhile, the agent in charge told the ROV operator to return to the "boulder" and bump into it. It moved - it was not a boulder!
UW: What are the biggest factors in a body search of this type being successful?
GR: Having accurate location information is essential to minimize the search area. Calm water conditions are also a great benefit. Surface wave action from wind or passing boats can cause smearing of the side scan images and render them worthless.
Of course, the bottom conditions are also important. A smooth, clean bottom with no trees, large boulders, or other debris that can hide the object you are looking for is very desirable.
UW: Let's talk about equipment. What exactly did you use on the Laci Peterson search?
GR: We used a customized Marine Sonic Technology side scan sonar. We have a custom-made stainless steel tow body for the 600 kHz transducer. The tow fish is six feet long and weighs about 130 pounds. The extra length makes it more stable and, consequently, the images are better. The
heavier weight allows us to work in deeper water with less cable.This setup requires the use of a powered hoist to deploy the system. Our hoist has a variable speed electric motor with a remote control and is also equipped with a slip clutch to prevent cable breakage if the tow fish snags on something underwater. We also used an aluminum tow body for the shallow water in San Francisco Bay. The lighter weight of the aluminum gave us greater layback and tended to somewhat de-couple the towfish from boat pitch and heave due to surface wave action.
UW: Do you use different units for different searches, why or why not?
GR: We use the aluminum tow body when we have to air freight the equipment and use a boat of opportunity. We have lower and higher frequency transducers available for use in searching for larger or smaller objects. The 600 kHz frequency is the best all-around frequency for most of the underwater
searches we have conducted.
http://www.findlaci2003.us/sonar-gene-ralston.html
