Topic: 997 SI- Range setting &depth

[BalticProject]

Hi.
Three weeks ago finally I became a happy owner of HB 997 SI.Since that time I used it two times only,so I'm very begginer.Before I was using HB Matrix 47 3D but that model  was below my expectations.
Mostly I'm gonna use my new 997SI for  serching II WW shipwrecks and planes within my area (Baltic Sea, Poland, small town Darlowo)
Recently I tested my echosounder on 180' wreck of bulkcarrier(sank in 1984)

My quetion is:
What should be the  range setting/depth ratio to achive best image?How wide must be the "inside channel"?
Rgds
Michal

[RGecy]

It depends on what you want to see.  Here is the kicker, if you are in 80' of water and you have your range set 100', well 80% of the screen area is going to be just dark area from the water column.  You would want to set you range to say 200', and now you have more visibility.

Now, in shallow water say 20' deep, 200' may be too wide.  Now you can drop it back down to 100'.

I would say a good rule is to always set the range at least 2 times the depth of the water.  As it gets deeper, we know this number will get smaller.

Good Luck,

Robert

[George]

Michal

You might want to try a speed between 2 - 4 MPH and play with the side imaging going from shallow to deep water. Take the time to learn what the system is capable of, it might help you to better understand how to get the most from the unit.

I believe that some of the folks that are looking deep have modified the SI transducer on to some kind of a fish which is trolled deep carrying the transducer.   

[sixwarden9]

I have searched the posts on this site and others and found that most people are using 2 to 3x the depth
for their range. I took mine out for the first time last night in calm water
ranging from 4-25 feet with the range at 150. When my range was at 150, I did
not appear to get a full picture, both the left and the right sides of the image
were dark, no pixels on the screen active. When I dropped the range to 100-120,
the pictured filled the screen. My question is:

Should I be getting more picture (with less detail of course)or is the width of
the sonar return relative to depth, i.e. deeper water, wider return possible?
All of my scanning was at 455, when I switch over to 800 KHz it was virtually black.

My unit was set to defaults.

[RGecy]

At 800khz, the beam angle is smaller and actually will not reach as far at shallower depths.  The 455 should give almost 180 deg coverage, but again at 4' depth, you will notice some shadows.

Here are some images showing the beam coverage.

Robert

[sixwarden9]

All of my scanning was at 455, in 20 ft with the range set to 150, should I be getting a full picture?  About the 800, I could see the water column, but nothing else, I tried scanning the boat ramp and a known point.  It was black.  I am going back out today to try changing the settings and or adjusting  the transducer.  I am looking for a baseline of what to expect.  When I decreased the range, it filled the screen, I just want to make sure that I don't need to move my transducer, i.e. if I was in deeper water I would be able to see out to the sides further.

Thanks,

Matthew

[Humminbird_Greg]

Matthew, in 20 feet of water you should have gotten a sonar return from the bottom with the 800kHz setting.  This makes it sound like something is not quite right combined with the dark outside edges when set to 150 feet.  Can you test you unit on someone else’s boat to see if the results are the same or not?  Maybe post some images of your transducer installation so we can see if it looks like something is obstructing any of the Si sonar?

[sixwarden9]

Greg, in 800, I can see the water column and the bottom, but it is virtually black, the bottom is soft. In 455 I was able to see things just fine, but I had to lower the range to fill the screen.  My main question, concern is: should I be getting a picture out to greater ranges in 5-25 feet of water or is range relative to depth.  I did not know how to take screen shots and it was late so I pulled out an came home.  I am playing hooky from work today and learned how to take pics so I will post them later if I can't get it figured out.  I also posted this question on yahoo.  I have a ranger with a thru hull under the setback.  It is not permanent yet, no sealant.  I tried it first with the fairing inside the hull and then with the fairing outside the hull to lower it.  I am made some different thickness test fairings (1/2 in to 1 in) out of plastic that I am going to try today.  There is a temp probe from my other sounder that may have been giving me trouble when I first started.  It is 1/4 high by 3/4 long.  On the thru hull, where does the sonar eminate from, does it start from the flat portion, or where the transducer starts to curve?

Thanks,

Matthew

[sixwarden9]

Couldn't figure out how to post an image, so I emailed them to you Greg.  Someone want to clue me in?

[Jolly Roger]

Hi Matt,
when you post a reply, there is a button on the left side below the field where you type in your text. It says "Additional Options".

Click there and search for the picture you want to post by clicking the "Search" button to the right of the field "attach".

It took a while for me as well until I figured this out 

[sixwarden9]

I see said the blind man, thanks Jolly Roger.  Here is the difference between 455 and 800. Both pictures are of the same boat ramp.  In the 455 it is on the left and in the 800 it is on the right.  The 800 is very dark.

 

[RGecy]

I would say that the depth is more of the issue.  The 455 looks great, but at 7' deep, you are only going to get about 40-50' to each side max.  I guess we could figure the distance based on the beam angle, etc.  But, I think you understand.

It also looks like your transducer may be tilted up just a little on the right side.  You can see the bands where the signal disapears are not equal on each side.

Robert

[sixwarden9]

Robert,

Enlighten me.  I understand that the 800 shoots down at a greater angle, so there will be less side range, also I would believe a harder bottom would be needed as the shorter wavelength is probably absorbed more than the longer 455.  Mathematically speaking, is there a fairly simple formula for expected range based on the angle or even a complex one will do.  I will just have to write it on my big chief tablet.  I never can remember all the formulas for working with triangles, but I suspect it will have sin and cosine in it somewhere if you use 90 deg. as one of the angles in the 800 beam.  Trig class was a long time ago.

Thanks,

Matthew

[RGecy]

Mathew,

OK, here is the the formula we need.  Tangent(A) = y/x  With y being the SIRange, x being the Depth and A being the Beam Angle from center line to outermost leg of the beam.





So we need to solve for Y.  Our equation should look like this: Tangent(A) * x = y  or in other words Tangent(A) * Depth = SIRange

We know that according to the Humminbird literature that the coverage for 800khz including the 83/200khz under the boat, is 130 degrees.  Half of 130 = 65 degrees and this would be our angle A.  (Hopefully the Humminbird guys can shed some more light on this figure so we can be a little more accurate)

Tangent(65) =  2.1445
Lets say our depth = 10'

So 2.1445 * 10' =  21.445'

An easy way to think about it would be to multiply your depth by 2.1.  And just to be safe, since depth is always changing would be to use a multiplier of 2.5 or even 3 times your depth.

Hope this helps,

Robert

[sixwarden9]

Outstanding, I am going to copy your post and print it out so I can work through it by hand.  For 455 it would seem a bit harder to do since it is more rectangular than triangular. 

Thanks,

Matthew

[sixwarden9]

OK,

Still working this through, you used 130 as the coverage because it includes the 2d sonar.  You divided that in half because why?  If it was 180 it would shoot straight out the the side, but because 800 shoots out at 55 deg. it is not square, so total coverage is 130, divide by two to make one angle of the right triangle?

[sixwarden9]

Duh!  130 deg is both the left and the right sides, hence the division by two giving you half of 800's total coverage area.  So 455 in theory should give you max range regardless of depth assuming a perfectly flat bottom of the right density.  Except, it comes out of the transducer at 84 deg. and not 90 leaving a 6 deg gap at the top.



So could we use your formula on the 6 deg triangle and extrapolate a number?  My second year of engineering calculus taught me that I was not cut out for high theory math and I should stick to getting a science degree.

My head is spinning, but I am addicted to learning (sometimes totally inane stuff) and figuring things out.

Matthew

[RGecy]

Matthew,

Your drawing is a little off, 84 + 6 should equal 90 degrees.  But, however the beam is angled, you will get complete coverage with the 455khz.  I can pass a floating dock and see the floats just under the surface on the SI and will get almost total coverage under the boat as well.  The 6 degrees is minimal comparatively!

Robert

[sixwarden9]

Robert,

Thanks for your help in my better understanding the way that the beams come out of the transducer, I was back on the lake last night and I have everything set now.

Matthew

[reso]

guys, if we know the angle of the si beam, we have the bottom returns from the si , and we know the position of the boat and the actual depth under the boat. Is it then possible to calculate also depths for the bottom that the SI reflects from.
we can (martin at least for humviewer) get a position on the si screen to the sides from the  boat if we know the heading of the boat. Is it then impossible to calculate the depth from the si returns (in other words make a big sweep of the bottom with lots of depth data for e.g. drdepth instead of just the depth from the signal under the boat)?

reso