Author Topic: Distinguishing objects/varying image size  (Read 10367 times)

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Offline Mark 64

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Distinguishing objects/varying image size
« on: February 17, 2010, 01:19:37 PM »
Hello all,

Newbie signing in - have been looking at the Hummingbird 997c and 1197c for quite some time now but cant quite make up my mind.  I know the 1197c can be attached to a larger screen but it seems a lot of money for that option.

Firstly I cannot seem to find images of the type or at the depth I'm interested in - say for instance a 7ft cannon or any metal object that sort of size at roughly 10- 20 metres.  Will these show up on the unit?
If these side scan units cover a rough area of 800feet can this be reduced and if so does this enlarge the object on the screen?

Thanks


Newbie



Offline keizerh

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Re: Distinguishing objects/varying image size
« Reply #1 on: February 17, 2010, 01:43:35 PM »
buy a 998 or 898.
Smallerscreen, but same options as 1197.

hendrik

Offline sonar2000

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Re: Distinguishing objects/varying image size
« Reply #2 on: February 17, 2010, 02:03:46 PM »
Mark, whle the Si imaging covers a lateral side to side distance, article such as you suggested are a bit reduces at the outboard of the scan.  sonar is a little of an art in that you will need to spend some time just using the unit to get a handle on operation, settings, menus, and a few other distinct pieces of the unit.  Ffinding an object sometimes can be time consuming as you scan a large area and then see nothing.  Most of the time unless looking for the titanic we try to keep our side to side distance around 60 feet.  you will develope a feel for this as you gain confidence in your unit. This forum has a lot of pictures and postings and I would suggest that you spend some time going thru the topics that appear to be interesting to your needs. then get some water time and play play play.  another shortening of the learning curve is to buddy with fishing folks who are users and have them tutor you on some of the specifics as they have found thru use.  Depth is a consideration on objects and depending on the size depth can be a limiting factor.  I think you said 50 to 60 meters and that does stretch the imagination a bit on smaller targets.  Something we do is side to side and  locate something of interest and then run a closer distance to get a better image.  Final hint is to record and then view in the HV44. you will get a clearer picture on the viewer.  chuck

Offline sonar2000

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Re: Distinguishing objects/varying image size
« Reply #3 on: February 17, 2010, 02:05:22 PM »
Mark, my fault.  10 to 20 meters is real good for depth......   chuck

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Re: Distinguishing objects/varying image size
« Reply #4 on: February 17, 2010, 02:14:11 PM »
Hello Mark64 and welcome to the forum,

looks like we have another treasure hunter on board  ;).

If you like to see stuff laying on the ground, first of all it has to stick out of the ground to produce a sonar echo which you can recognize on your screen.
To get a relatively good image of the ground there are different factors which have to be fullfilled.

Chart speed in relation to boat speed is one factor: http://forums.sideimagingsoft.com/index.php?topic=242.0

Another thing which you already found out:
Side Range in relation to water depth. When I started out with side Imaging, Robert told me to use 2 - 3 times the water dept as Side Range and I had good results with it, i.e. 20 metres water depth ---> 50 metres Side Range.
This is gives you a decent picture of what's going on downstairs without sacrificing picture detail or area coverage.

Now finding a 7ft cannon in 20 meters will be a challenge I think. Depending on the sea ground and the direction you run along or about it, I guess you might be able to find the cannon if it is sticking out far enough.

Concerning the screen size: The bigger the better!
I wish I would have a 1197 on the water for its larger screen. But as Hendrik already mentioned, the 998 might be an alternative. It also has a video-out port with which you can feed lets say a 12V flat screen. But then on the other hand: If you don't have the screen already, it will cost extra and there is an extra electronic item added to your boat that might break or get stolen.

Just my two cents and I hope it helps.

Regards / Harry
YES,......
WE SCAN!

Offline Kimi

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Re: Distinguishing objects/varying image size
« Reply #5 on: February 17, 2010, 02:16:54 PM »
say for instance a 7ft cannon or any metal object that sort of size at roughly 10- 20 metres.  Will these show up on the unit?

Probably not!
The problem is not that your sidescanner cant see it. The problem is that your self maybe not understand whats on the screen.

The sidescanner works like a camera taking "greytone" pictures. If you paint a canonbarrel whit "citycamo" patterns, and put it out on a yard full of sand and rocks etc. And then take a picture in bad light conditions and whit low resolution from a roof and long distance. Would you find the cononbarrel on the picture. Probably not?

But, if you place the same canonbarrel on a sandyard, and taking i picture, still with a lowresolution greytone camera. And if you taking the picture in an low angle, and using a flashlight. You would see somthing. Maybe you could only see the shadow. But something anyway.
 
Wery few wrecks are so called "Donald Duck" wrecks. Uppright standing with masts and all. Most wrecks are "wrecksites". They are in pices over an bigger area. The canons would be difficult to identify ewen if you would dive among them in the wreck.
 
Its all about learning to understand how your unit is working. And the only way to learn is to using your unit as much as possible. And then you need good scanningconditions and a little bit of luck.
 
The picture below is from the swedish battleship Gustav Adolf sunk 1788. Its layin outside Helsinki in gulf of Finland on a deep of 18-20m. The wreck is full of big 36 pounder cannons (71ps). The lenght of the barrel is about 7-9ft. Can you see them?
 
Kimi... ::)
 


 
« Last Edit: February 17, 2010, 02:26:06 PM by Kimi »
homepage: ( in Finish only) www.wreckdiving.yolasite.com

Offline sonar2000

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Re: Distinguishing objects/varying image size
« Reply #6 on: February 17, 2010, 02:23:17 PM »
good picture from Kimi.  check the forum topic board General Pictures and Screen captures.    There are a lot images to browse thru.   look not only at the picture but for those screens that have information like depth,  speed so that you can get an idea of unit setup.  Chuck

Offline Jolly Roger

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Re: Distinguishing objects/varying image size
« Reply #7 on: February 17, 2010, 02:24:17 PM »
Wow Kimi,
That's a nice shot!
BTW: A picture says more than thousand words and I really like your explanation about the city camo in the sandyard  ;).

Regards / Harry
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Offline keizerh

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Re: Distinguishing objects/varying image size
« Reply #8 on: February 17, 2010, 02:41:53 PM »
You also can do a rough scan with your transducer to determine the highest points of the bottom.
Then you use another transducer on a towfish, that you hoover just above the highest point to get clearer pictures.

Hendrik
(Who is waiting for a HB098, without a screen to connect to his Simrad NSE12 ;-) )

Offline Mark 64

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Re: Distinguishing objects/varying image size
« Reply #9 on: February 17, 2010, 02:57:29 PM »
PHEW! 

Have now got the missus reading all the info as she quicker than me   :o Thanks very much for your rapid responses - just to clarify couple of things then;

so you can reduce the scan area sideways on both the units which will result in clearer picture?

The city scape concept really helped and the picture was fab, thanks Kimi.  I think at first glance I could probably see 5 or 6 on the right hand side, but I would be guessing because of the size and the straight lines which is unusual on the seabed.

I have found 3 cannons sitting amongst rocks and 1 just proud of rocks by the linear shapes and was wondering if the sonar would send up a clearer picture because the difference in material between the cannon and the rocks/seabed?

All that said I will now go away for couple of days and read thru all the info you have pointed me towards and will be back soon - and aren't all us boys treasure hunters at heart?!  ::)

Newbie

ps  is the 998 out yet and can this connect to a bigger screen?  Because you can get a 22" flatscreen pc monitor for about £140.

questions questions questions!

Offline Jolly Roger

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Re: Distinguishing objects/varying image size
« Reply #10 on: February 17, 2010, 03:22:20 PM »
Mark64,
since you referred to Pound as your currency:

Call Ian at G-Comm and ask if he got the 998 already in.

G-Comm
IMSCO HOUSE
SOUTHTOWN ROAD
GREAT YARMOUTH
NORFOLK NR31 0HU
Telephone +44 (0) 1493 669966
www.g-comm.co.uk

an is really taking care about business and has decent prices (at least he had last year  ;D).

The 998 can be connected to a bigger screen as long as the screen has a video-in port  ;D.
About the difference in appearance of cannons and rocks: You wont see a difference in reference to colours, because both have a hard surface and will reflect the sound waves in the same way.
Robert posted somewhere about the Side Range and the picture quality. Can't find the post at the moment, but I think he'll jump in to give more details.

Regards / Harry
« Last Edit: February 17, 2010, 03:50:49 PM by Jolly Roger »
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Offline keizerh

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Re: Distinguishing objects/varying image size
« Reply #11 on: February 17, 2010, 04:13:22 PM »
Same is true for the 898 with an even smaller screen, but with video output.

hendrik (who is wating for the vc1 videocable to check te quality of the output)

IRC Kevin

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Re: Distinguishing objects/varying image size
« Reply #12 on: February 18, 2010, 10:44:20 AM »
Hi Mark and welcome to the board. I've picked up a 2 foot square outboard at 120 feet depth on Windermere, where the signal is degraded considerably by all the algae in the water. In shallower water it's much better. The photo below shows an old jetty that was towed out from the shore and sunk. If you look to the right hand side of the jetty, in the centre of the end,  you can see the 17mm diameter rope it was towed with, leading up to the 'one o'clock' position.  (I know the rope diameter is correct becuase I've spoken to the guy that dumped it)



The secret to not missing finds is to record everything and then review with the HB back on the berth, save a copy to your PC and then go over it again with both Humviewer and Si View.

By the way, Harry is spot on about G-Comm. Cheapest by a long way in the UK and fantastic service too.
regards,
Kevin

Offline sonar2000

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Re: Distinguishing objects/varying image size
« Reply #13 on: February 18, 2010, 11:02:45 AM »
great pictures.  you are so right on with your comments.  As Robert said,  the proof is in the picture. Yes small ropes will show.  great picture of this.  George sent me a sonar in which the posts and cables show up.  This stuf is capable.  The key to HB sonar is the external viewers.  Well and getting the unit set up.  We here in our group are excited with the humview and the tracks with sonar beam  We think that will cut down on the number of tracks to scan an area.  Add me to you avitar.  My one cell brain hurts,    Chuck

Offline mendota

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Re: Distinguishing objects/varying image size
« Reply #14 on: February 22, 2010, 10:13:30 AM »
I think it is important to emphasize that the video output on the 1197 and presumably the 998 is at the screen resolution only - you will not see better sonar resolution on a large TV screen - it's just a blown-up version of the existing screen on your sonar.  DO NOT buy a large-screen display for your boat thinking that  you will gain some advantage.

On the other hand, HB recordings apparently contain the full resolution of the sonar, and the 3rd party viewers (Humview, SIView) are capable of displaying this full resolution in all its glory, if your display is big enough.  I would suggest a 22" wide-screen at a minimum, as my 19" is not big enough.

Truly amazing what additional detail is evident at home vs on the water.


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