Recreational side scan to find wrecks

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One important factor many forget to attach with positions is the datum the sounder is set to. I use WGS84. The difference between positions with different datums can be hundreds of metres. My Garmin map shows map positions for wrecks shown as a circle (clearly from an existing map) unfortunately after locating the wreck I have found that the map spot is from AUS66 datum but put onto an electronic map using WGS84 so some 100 metres out east/west and 160m out north/south. And the errors are consistent on the electronic map. So I would suggest you ask the person supplying the information what datum they are using. If you get a blank stare, it probably means they have no clue as to what the GPS was set for.

I'll have a play with that, some of the sets have geographical features so i checked they lined up on the map and was happy, i didn't consider that different sets might be different datum's
 
Totalscan is 455 & 800 Khz. Garmin has 260 & 455.Simrad claims 600 foot range but in reality you'd be lucky to get 250 on either side in saltwater even at 1 knot speed.I get 390' each side reliably from 80' to 200'.Since the distance shown is actual including transmission angle you are really netting less true horizontal distance and want all you can get.

You get higher resolution with higher frequencies but no penetration,particularly in saltwater and only being driven by 500watts rms.

Once you start getting into 80 to 100 feet the Lowrance is terribly outclassed perfomance wise.Lowrance does have nice features and GUI but to find wrecks you want range.Once you find the wreck you can switch frequencies and get detail.

Dragonfly doesn't support side scan that I could see.
 
Looks like I can get the Garmin Striker Plus 7sv with GT52HW for a lot less or the EchoMap Plus 75sv with GT52HW for slightly more than the HDS 7 Gen 3 with Total Scan.

I'm going to have to do some more research as I haven't looked into the Garmin products much. They only list the GT52HW as doing SideVu on 455 and 800khz. They give a beamwidth of 2 @ 455 and 1 @ 800. Are you able to shed any light on what the beam width equates too? This transducer looks similar to the TotalScan

Looks like I would have to go up to the CV51M-TM to get SideVu at 260 and 455hz (appears to lose the 800) and possible a power increase in SideVu from 350W to 500w but this is harder to confirm since they appear to combined ClearVu and SideVu numbers at times.
 
Beam width doesn't really matter as it is fore and aft
GT51 is the one,saw it in package deals w Chirp Echomaps pretty cheap over the holidays.
GT41 loses Chirp on traditional,but has Chirp SS.
After a lawsuit they are switching to CV designation.
 
Unfortunately it doesn't look like the reef master software I panned to use to put all of the scanned images together supports the garmin and the garmin manual is a little lighter than the lowrance, can it save the side scan images to export to other systems?
 
Yep,you an record it ,play it back and make mosaics using appropriate software.The bass fishermen are really ahead of the curve on this ,there are several tutorials online from them.
I assume Arcgis could work.
 
I'll have a play with that, some of the sets have geographical features so i checked they lined up on the map and was happy, i didn't consider that different sets might be different datum's

Its not so much that different sets have different datums, rather that most sets can have their datum changed to a number of different map datums. The most common I think now is WGS84, however in australia, historically many maps were based on AUS66 which means the coordinates taken from one map cannot be used directly onto another, same with sounders, unless you change the datum on your sounder, enter the position based on the new datum, then after doing that and saving it, change the sounder datum back to the original setting and the positions should calculate out using the new datum.

There are conversion programs to convert a position from one datum to another.
 
The last boat I had was equipped with side scan. I had an absolute blast with it. When the fish weren't biting I would just toddle around looking at stuff to see what I could find. The older fish finder I had often would not show anything on the bottom that was shown on nautical charts. Then my uncle {captained the research vessel for the UMD} explained it...he said that whenever you see on a chart a little circle of dots and the letters "obst rep pa" {obstruction reported, position approximate} this is where someone reported to the USCG something in the water, but the USCG was unable to find it when they went out and "sounded" for it at that spot. As opposed to the little boat with the letters "wk" for wreck. Doesn't mean it's not there or at least nearby, or it seems like they must never take any of those obstruction marks off the charts, so it could be corroded away to nothing by now and there is nothing left of whatever it was to see. When I got the new side scan I was able to find some of the charted objects. Sometimes I could tell what they were, sometimes it was too far gone. A lot of fun never the less. Also confusing on the charts at first was the letters "PA", in capitals...this designates "private aid" which is a channel marker {usually just a stick} or a homemade buoy someone other than the CG has placed for whatever reason.
One other reason I found for stuff not there was local lore. The Chesapeake bay and her tributaries have many "rock piles" that are well known places to catch fish. I couldn't wait to go and check them out with my side scan...only to find that better than half such places had no rock pile or anything else there...but apparently fish. Sure enough, when I asked the old timers why they believed there was a rock pile or other obstruction they said, "well, there must be somethin', we always caught fish right there."
 
From everything that has been said here and further reader I prefer the interface, wireless app support and Reef Master Support of the Lowrance but the transducer (GT51) on the Garmin with 260khz SideVu, and if i can't find what I want then nothing else matters.

However I can only find a Echomap 95 with the GT51 (which is the old version), the Echomap Plus comes with the GT52. The local shops can't get the Plus in a package with the GT51 and Garmin support haven't answered about being able to, so if anyone knows where I can get them together in Australia let me know, because the budget doesn't stretch to buying the GT51 separately.

On a good note I might i have found some local with a Lowrance with Structure scan who has said they will take me out and show me how well it works so at least i can confirm that it is good enough with just 455 and 800khz
 

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