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  1. #1
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    Whats going on here?

    In this 2d and downvu pic of the same spot, what is 2d doing in this situation with the ghost-like representation of the rock?

    Is it just a matter of the rock being on the outside edge of the cone?
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    Last edited by Chief Brody; 06-16-2019 at 08:09 AM.

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    #2
    I agree it looks a little strange. Really sharp looking down image.

  3. Member Wayne P.'s Avatar
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    #3
    2D sonar has a somewhat inverted cone shaped pulse and "stuff" is within the coverage a lot longer than it is with any of the imaging technologies.

    Wayne Purdum
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    #4
    Wayne, your downvision shot is even crazier looking than mine

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    #5
    this is awesome down image!
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    #6
    Looks like a termite eaten tree trunk!!

    John

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    #7
    I dropped the ball on this one: my shot is from Homeport, but I didnt use it much because its about useless for sidescan. But i couldve got some good 2d and downvu recordings with shots like mine

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    #8
    ??? Is Homeport useless for side scan on is the unit?

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    #9
    ya still pretty much useless for sidescan. I didnt realize it was still useable for 2d and downvu, though.

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    #10
    Quote Originally Posted by Chief Brody View Post
    In this 2d and downvu pic of the same spot, what is 2d doing in this situation with the ghost-like representation of the rock?

    Is it just a matter of the rock being on the outside edge of the cone?
    what color schema you used for this downvu? I seem cannot find anything close to this color with EM+ 93sv, does that mean ultra has more color schema than 93sv?
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    #11
    Quote Originally Posted by Wayne P. View Post
    2D sonar has a somewhat inverted cone shaped pulse and "stuff" is within the coverage a lot longer than it is with any of the imaging technologies.

    is this downvu from Echomap ultra as well? it's very like the bird's mega/mega+ color, would you share the color schema name?
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    #12
    Quote Originally Posted by canon View Post
    what color schema you used for this downvu? I seem cannot find anything close to this color with EM+ 93sv, does that mean ultra has more color schema than 93sv?
    Ill have to take a look again tmrw, but pretty sure it was orange crawfish(?) and then amber in Homeport.

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    #13
    Quote Originally Posted by Chief Brody View Post
    In this 2d and downvu pic of the same spot, what is 2d doing in this situation with the ghost-like representation of the rock?

    Is it just a matter of the rock being on the outside edge of the cone?
    Whats going on is a result of how downsvu works vrs 2D.

    You have to remember that a downvu image is basically what you get if you draw both sides of a sidevu image on top of each other at the same time. Downvu "sees" off to both sides of the boat using a very narrow (front to back) cone - just like sidevu. The difference is that sidevu draws the right and left images on opposite sides of the screen - and it scrolls down from the top.

    Downvu "sees" the exact same returns - but - it draws them both at the same time right on top of each other. That can often make for muddy, confused, and distorted images. When the structure is mostly or only on one side, then you get the pretty pics.

    Heres an example of a 2D, sidevu and downvu images of the same piece of bottom that shows whats happening with some logs that were almost dead center when I passed over. You can see what was an almost straight log that looks bent and under the ground, but its really just the two sides of the same log on sidevu drawn on top of each other.

    The 2D looks totally different because it is also drawing things from both sides, PLUS, its drawing things that are ahead of and well behind the transducer - all at the same time. In my case, there isnt as much difference as your pics mostly because the bottom where I was was really flat.
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    Last edited by Larry3215; 06-21-2019 at 12:08 AM.
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    #14
    Sorry, grabbed the wrong 2D image. Fixed now.
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    #15
    Thanks Larry

    Ya it was the 2d image that had me wondering. i always thought the 2d cone would see the edge of an object that was higher up and draw it as the bottom. But in my case it drew it along with the actual bottom.

  16. Member Wayne P.'s Avatar
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    #16
    Quote Originally Posted by canon View Post
    is this downvu from Echomap ultra as well? it's very like the bird's mega/mega+ color, would you share the color schema name?
    Not only is it like Bird's MEGA Imaging, it is from a + model. Posted it as example of how 2D sonar does not match Down Imaging due to the very different coverages.
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    #17
    Quote Originally Posted by Wayne P. View Post
    Not only is it like Bird's MEGA Imaging, it is from a + model. Posted it as example of how 2D sonar does not match Down Imaging due to the very different coverages.
    what color schema you using like that? Amber? I really like the color, want to setup like that
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    #18
    Quote Originally Posted by Chief Brody View Post
    Ill have to take a look again tmrw, but pretty sure it was orange crawfish(?) and then amber in Homeport.
    I cant seem to have similar color either by adjusting with orange crawfish or amber. let me know once you looked. Thanks.
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