Topic: what's up with this depth reading?

[slabbacks]

Why is the depth reading showing deeper than the SI is showing?  Anyone notice this before or heard anything about it?

[Monticatgeek]

Why is the depth reading showing deeper than the SI is showing?  Anyone notice this before or heard anything about it?

I don't see anything out of the ordinary with this screen shot. it looks like you were in 7 feet of water and had the unit set to view 25 feet on each side of the boat. I also noticed what appears to be spawning beds to the left of the boat. unless I am missing something I think your unit is fine.

[slabbacks]

I may be looking at to hard but if center line to bottom is seven feet how is center line to the first side line only 6'?  went back through some other shots and found it looked strange in this shot as well.  shows 59.8fow but lines show less than 52.  Still puts me on fish and cant complain but just thought is was weird when someone brought it to my attention.

[newkid4si]

slabbacks

    If your looking at the top image in HumViewer, change your view from SI to 2D. It would be interesting to see what the depth would be in 2D.

            Mike

[slabbacks]

Good idea.  I'll go check it out now and let ya know what I find.  THX!

[slabbacks]

depth was same as reading on SI screen.  Must have something to do the way SI is displaying the info in reference to distance from the boat.   When using the SI to scan and mark a new structure, I have no problem getting back to it so I think this may just be a fluke and shouldn't be worried about.

Heading out in the morning...most should be back to work with (i hope) a little less traffic on the water. 

[Monticatgeek]

those numbers to each side are how many feet to the side the unit is seeing. you have your si range set to 25 feet on each side of the transducer. the line with the 6 means 6 feet to the side. it is not the depth there. you can go into your menus and turn those range lines off so it doesn't confuse you.

here check this out. it is from humminbird website.

http://www.humminbird.com/Category/Technology/Side-Imaging/

[slabbacks]

thx but not confused about it.  Just curious

thx again

[newkid4si]

This post brings up an interesting question. Sonar works on sound and time. The sound wave is transmitted at the transducer. It travels out in a 180 degree arc (SI), strikes an object, is reflected back, is received by the transducer and the power head converts the time into distance. An object 30' to the left or right would have the same time as an object 30' directly under the boat. The transmit frequency is the same. I can understand the left/right part (two piezos), but how does it know if a 30' target is at the surface, directly under the boat or at a 45 degree angle on the same side because it's all the same amount of time.

                        Mike

[slabbacks]

Bud we will have to get one of the higher ups to answer that one.   Went through shots from over the months and noticed that not all has had  this take place.

[rnvinc]

This post brings up an interesting question. Sonar works on sound and time. The sound wave is transmitted at the transducer. It travels out in a 180 degree arc (SI), strikes an object, is reflected back, is received by the transducer and the power head converts the time into distance. An object 30' to the left or right would have the same time as an object 30' directly under the boat. The transmit frequency is the same. I can understand the left/right part (two piezos), but how does it know if a 30' target is at the surface, directly under the boat or at a 45 degree angle on the same side because it's all the same amount of time.

                        Mike

The processor does not know at what angle any echo target is...it just paints the echo target at "x" range away from the xducer...

It's the shadow and your mind's eye that interprets vertical angle into the SI image...



If the anove depiction did not have the shadows of fish 1 & 2...the actual fish targets (in the SI image) would look to be at the same angle from the xducer....but clearly they are not...
 
Experiment this yourself...cover up the shadows of fish 1 & 2 in the SI image and then look at the actual fish echoes...

Rickie

[Humminbird_Greg]

Bud we will have to get one of the higher ups to answer that one.   Went through shots from over the months and noticed that not all has had  this take place.

slabbacks,
Can you go back and remember any menu settings that could be causing this?

[slabbacks]

Rickie reading that I can tell which fish are higher in the water column and which one in closer to bottom with the help from the shadow.  Without it they are just under the boat.  thx for the px

Greg, I was going back out today but I guess the sun and water whopped my butt lol.  Woke up way after sun up with one heck of a farmers tan...look like a boiled lobster.  Will be going tomorrow for sure.  I am going to go through the settings I have now then make some changes in regard to off set and others and run passes on the same track and get shots to compare.  It has to be in there somewhere and not really the unit.

Like I said, I can scan a large area...mark the structure and get right on top of it in 2D.  Yesterday I scanned a large open area of channel and marked some good looking deep structure.  Both man made and natural (drops, points and timber).  Went back watching the map and flipped over to 800 to get a better look.  The only thing that I can think of and see in my notebook as far as a change in setting for this lake is map off set.  Sen. and Contrast are always changing depending on many factors.  Other changes no doubt where made over time but must have been changed back due to not being logged down as a change.

[newkid4si]

Well Duh! I knew that. Robert posted a similar explanation way back at the beginning of time. It had just slipped my memory ( along with several other things).
You get caught up in transducer installs, this software/that software, links etc. Sometimes you don't think about the basics. Thanks for the refresher Rickie.

          Mike

    I have no idea how Greg keeps up with all of this. The man is in a league of his own. We are truly blessed to have him. The day he posts that he is hanging
    up his keyboard, I'm going to have a panic attack.

[rnvinc]

    I have no idea how Greg keeps up with all of this. The man is in a league of his own. We are truly blessed to have him. The day he posts that he is hanging up his keyboard, I'm going to have a panic attack.

I agree 100% ...on both points...

Rickie

[slabbacks]

Could you imagine how good he would do as a consultant with his own business?  Man has probably forgot more than I have learned on the subject and still is a wealth of info.

Know what ya mean when it comes to forgetting stuff that has been covered.  My phone has px of things I've read about and the notes go on for days...but for me it's fun and I can't complain about the fish it's put me on 

[Humminbird_Greg]

I appreciate the comments guys.  I do forget stuff all the time but have tons of notes and many of the CRC folks and Engineering here to help keep me in line.  I just wish that I had the time and brain power to learn more.  Don’t worry, I’m not going to post that I am hanging up the keyboard - according to my Wife I will die at it!