Rob,
I don't think you'd need a high end unit to find your ship PDQ.
Something like this ought to do ...
(http://www.limbatus.net/linked/LTT-JR-tm-picture-001.jpg) (http://www.limbatus.net/linked/LTT-JR-xl-picture-001.jpg)< click to enlarge >(http://www.limbatus.net/linked/LTT-JR-tm-picture-002.jpg) (http://www.limbatus.net/linked/LTT-JR-xl-picture-002.jpg)
=> (http://limbatus.net/linked/tm/LTT-post-picture-005.jpg) (http://limbatus.net/linked/xl/LTT-post-picture-005.jpg)
=> (http://limbatus.net/linked/tm/LTT-post-picture-006.jpg) (http://limbatus.net/linked/xl/LTT-post-picture-006.jpg) => (http://limbatus.net/linked/tm/LTT-post-picture-007.jpg) (http://limbatus.net/linked/xl/LTT-post-picture-007.jpg)
=> (http://limbatus.net/linked/tm/LTT-post-picture-008.jpg) (http://limbatus.net/linked/xl/LTT-post-picture-008.jpg) => (http://limbatus.net/linked/tm/LTT-post-picture-009.jpg) (http://limbatus.net/linked/xl/LTT-post-picture-009.jpg)
It does sound like a tailor made training OP / PR expo for your local LEOs to do a little SAR. I'd take you up on the challenge if you were a little closer ( Gainesville, Fl to: San Francisco, CA 94121 (https://maps.google.com/maps?saddr=Gainesville,+Fl&daddr=Spreckels+Lake,+San+Francisco,+CA+94121&hl=en&sll=37.771219,-122.494308&sspn=0.003202,0.004823&geocode=FbJyxAEdptIX-ykrLL9pISDmiDGWjRAoXXnngA%3BFdVXQAIdnOKy-CnRGPjwoIeFgDGrZrw9bgIHvQ&t=h&mra=ls&z=4) ~~~ Spreckels Lake (http://maps.google.com/maps?hl=en&lr=&safe=off&q=Spreckels+Lake+Golden+Gate+Park&ie=UTF8&hq=&hnear=Spreckels+Lake&ll=37.771219,-122.494308&spn=0.003166,0.004823&t=h&z=18&vpsrc=6) ).
Let us know what you turn up,
Darrell
Rob,
1) What, exactly, am I looking at in the photos?
The first and third shots show a Humminbird 798ci "bottom of the line" SI unit that is setup in a portable configuration. It runs off of a small 12V sealed battery. Both are carried in a small soft sided cooler. The second shot shows the transducer mounted on a "towfish" - which hangs over the side of the canoe. The last four shots are screen prints taken from a laptop that is using one of several freeware programs to review sonar recordings made using the Humminbird SI units. The sonar recordings are saved on standard SD cards. The first screen print shows a lake bottom which is around eight feet deep straight down and gets shallower on the left side all the way up to the shoreline. I would guess that your ship would show up similar to one of the small logs to the left side of the image.
2) What is meant by LEO?
Law Enforcement Officer
3) What is SAR? (Search and Rescue?)
Correct.
4) Would the unit in the photo work in 3' of water?
The towfish only needs to be deep enough to "see" under the bottom of the canoe.
=====================================================
If you had the right platform, it should be possible to mount a 798ci unit, a small battery and the transducer to one of your community's RC craft. A decent sized catamaran might work. You would need a laptop with the HumViewer program to review the sonar recordings on site. Power up the SI unit, tell it how wide an area to scan, set it to record and then put it in the SI view mode. Run one tract lane across the lake and one back about forty feet off from the first. Stop the recording, remove the SD card, plug it into the laptop and review it using the HumViewer program. That is just a rough outline. Here is a screen print from HumViewer showing the GPS tracklog (sometimes called a bread crumb trail) to the lower left. The blue dot is the vessels position corresponding to the SI image shown on the right.
(http://limbatus.net/wbdfishin/wbdrpts/wbdrpts2012/WB20120803/tm/picture-072.jpg) (http://limbatus.net/wbdfishin/wbdrpts/wbdrpts2012/WB20120803/xl/picture-072.jpg)
If all you were looking at was an up and back U-shaped path, it would be fairly easy to estimate the "target's" position. If you had internet access you could overlay the tracklog in Google Earth to get an overhead orientation. Here is an example ( from a different tracklog (http://limbatus.net/info/CKPTF-20110322/rpttm.html) ) of what is displayed in Google Earth ...
(http://limbatus.net/info/CKPTF-20110322/tm/picture-001.jpg) (http://limbatus.net/info/CKPTF-20110322/xl/picture-001.jpg)
Links:
HumViewer program (http://forums.sideimagingsoft.com/index.php?topic=155.0)
Humminbird 798ci HD SI Combo GPS Fishfinder (http://www.jandhproducts.com/_e/Humminbird_Fishfinders/product/Humminbird_798CI_HD/Humminbird_798ci_HD_SI_Combo_GPS_Fishfinder_407970_1.htm)
Sealed 12 Volt 8 Amp-hour Battery (http://www.apexbattery.com/universal-ub1280zh-replacement-battery-rw.html)
There was an old post I looked for and couldn't find that had a remote operated platform - so it has been done before. If you picked up a used 798ci SI unit and upgraded to the HDSI transducer, you could probably put the pieces together for somewhere reasonably less of the price of a new 798ci SI unit. I paid $150 for a new HDSI transducer (http://www.jandhproducts.com/_e/Humminbird_Transducers/product/XHS-9-HDSI-180T/HUMMINBIRD_XHS_9_HDSI_180_T_T_M_TRANSDUCER.htm) in 2011, but it looks like the price went up since then. You might get a used one from someone around here that's looking to move up to the LSS-2 transducer (http://forums.sideimagingsoft.com/index.php?topic=4532.0) .
Hope some of that filled in a few of the gaps,
Darrell