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Old 05 January 2006, 17:57   #11
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100 foot limit??

Bhampton,

They seem to state there is a 100 foot limit to the Hummingbirds have you seen this in use?

Might limit the potential for our diving requirements some what?
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Old 06 January 2006, 05:37   #12
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Tue,

Not used a side scan but spent two days using a commercial magnetometer off a rib in Poland. Results were disappointing if fact we couldn't even identify a known wreck. However towing a fish meant other boats in the area had to keep clear and you could only manage a very slow 4 knots or the fish skipped across the water. Achieved much better results with several ribs searching a small area with good echo sounders, Lowrance by choice.

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Old 07 January 2006, 13:41   #13
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sidescan

long time not on site got bored with lot of b0ll0cks while ago. but anyway was browsing and know a bit about surveying.

Hummingbird looks very good for price but limited to 35m side scan mode. Probably Ok for most recreational divers who stay shallow but if you are looking deeper would need more expensive towed array to make full use of side scan.

As with all modern devices experiment over known wreck or fishing spot to see what results to expect and look for before wasting time and no doubt money searching for illusive wrecks. Dual frequency sounders are very good alone with a sensible search pattern over known area if you can recognise the features you want. Dont show the area of side scan agreed so may take more time.

The benefits of something like a lowrance Combi recording unit are obvious that you can go home and analyse the area you have covered slowly in the warm comfort of your home and pin point the position for further investigation.

Speak to local fisherman who do actually fish the area your going to look at and see if they can help, a few beers can go a very long way. You may also be surprised that they know exactly where the obstruction is and avoid it to save their gear.

Good hunting

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Old 08 January 2006, 07:22   #14
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Thanks for all your responses guys. Very impressed with the images from the Humminbird, but most of the wrecks around here don't start until 35m so not much use.

I have all the lats/longs for the wrecks thanks to a very freindly angler (who's boat needed fixing ), and from other divers, skippers in the area. Plus I have pinged a few myself over the last year so actually finding the wrecks isn't an issue.

Since my original post my RIB has shrunk so a towfish setup would not be practical anymore. Is the Lowrance unit sidescan? and can I put the images onto my computer at home? As I would like some side scan images for a small film project I am doing next year.
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Old 12 January 2006, 05:40   #15
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Have emailed Hummingbird asking for clarification on this limit with 987, looked at their 947 which does 3D, this draws a wire frame contour map down to 75 metres which may be more usable and easier to interpret than the side scan though I belive it varies in how much it sees out to the side relative to depth.
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Old 12 January 2006, 13:06   #16
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From what I have seen more depends on the transducer than the actual display box - also with radar - a crap head unit and a nice big scanner are better than a good head unit with a small scanner.

Transducer range in price and power/size considerably - the one I fancied was 3000 for the transducer alone so maybe it would be better to budget for a bet6ter transducer with a cheaper head unit???
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Old 12 January 2006, 16:28   #17
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Did you know? When Ballard and crew finally found the Titanic using side scan someone happened to look at the survey ships depth sonar and it too was detecting the Titanic!
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Old 13 January 2006, 03:57   #18
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Hummingbird Teckernickel Support

Chaps,

HB's tech support got back to me, they have uprated the transducer so that it now scans 360ft out to each side and 150 ft down. Being 50 metres this is a bit more useful to leisure divers with a 50 metre limit.

The 947 with its 3D wire frame profile goes down to 75 metres which though less photographic in its image output may give a more useful on screen profile. Anyone know if they will be at LBS?
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Old 18 January 2006, 19:02   #19
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987 sidescan

on my web site I have some deeper scans, it was ruff that day an my little
zodak was getting bounced a bit.
it looks like 150feet is near max for the 455Khz beem I hafe received returns from as far away as 200 feet.
I am sure the 262Khz side scan would have more punch.
next time i take it out I will be testing the 262Khz in deeper water 100+
and also the very shallow 10- water.
the 455Khz beems go out and down at about a 45deg angle tell they hit the bottom and start drawing the topography.
so if your looking for a wreak that is at 100 feet you would need to be offset from it by at least 100 feet to even get it in the scan.
the 262Khz goes directly to the bottom then starts drawing the bottom.
so for finding objects and having better range the 262 may be better then you can image it with the 455Khz.
one of my scans on my web site has an image of a 1.25m fake xmass tree which sits at 40 feet.
I have a 512meg SD chip incerted in slot 2 that allows me to screen capture lots of scans which are bitmaps running at 1.2 megs each.
if you have any specific condition you would like to see tested let me know I want to test this thing good.
I just got a transducer mount that will allow me to mount it below the outboard currantly I am mounted to the transom on the left side of my outboard so the right scans are all but blocked.
this will double my area covered in one pass. woot!
brad
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Old 19 January 2006, 04:08   #20
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How about 200ft?

With the uprated transducer Hummingbird give a limit of 150ft what would a 200ft image look like, would you get anything on it or would it all be water coloumn?
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