Author Topic: Water Column rendering  (Read 196 times)

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Offline MikeP

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Water Column rendering
« on: December 29, 2019, 05:44:37 PM »
As I understand it, the Water Column is the black area directly below the boat.  And that it represents the vertical distance to the bottom without any lateral component. . This make sense to me because the bottom right and left side are a mirror image of each other.   Yet the water column image on the each side can be significantly different.  We've seen entire bait balls on one side and nothing on the other.   This makes me believe there is some lateral (like a cone) component to the water column image.  The Humminbird folded image video shows a pyramid shaped water column image but does not explain.   I'm just curious.  Thanks.


Offline rnvinc

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Re: Water Column rendering
« Reply #1 on: December 30, 2019, 09:40:30 PM »
The water column detail in the SI image is more than just a lateral line to bottom on each side left and right  ... (as you noted by being able to see bait balls in the dark water column area of the SI image)  ...

You are correct the HB “folded paper” scenario is misleading  ...

This diagram is a better representation of the SI image  ...


Because Sonar measures distance - every target that is closer to the xducer than the value of the water depth will be painted in the dark water column area of the SI image ...regardless of which angle that target is from the xducer  ...

The dark water column in the SI image should be interpreted separately from how the bottom detail is interpreted  ...

The HB software engineers took the sections of the bottom detail (left and right) and “shifted” those sections of bottom detail outward in the SI image to make room in the SI image for the dark water column  ...

Using the diagram below we can see how the sections of bottom detail have been shifted outward in the SI image to make room for the dark water column  ...


Rickie
« Last Edit: December 30, 2019, 09:48:15 PM by rnvinc »

Offline MikeP

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Re: Water Column rendering
« Reply #2 on: December 31, 2019, 07:18:22 AM »
Thanks. Wow.  Is this common knowledge?  I understand Side Imaging is primary a Structure Scan, but HB also sells it as a way to scan for fish too.   Before your explanation I sort of thought (although could not understand how)  the rendered fish were directly below the  boat and not the bottom vertical distance arc to each side.  Ive attached your image of the Shifted bottom detail with arrows connecting the arced image to the flat image.  Any idea how that is done?  Is this similar to rendering the 2D sonar cone to the flat screen image?  Thanks again. 

Offline rnvinc

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Re: Water Column rendering
« Reply #3 on: December 31, 2019, 09:45:09 PM »
Thanks. Wow.  Is this common knowledge?  I understand Side Imaging is primary a Structure Scan, but HB also sells it as a way to scan for fish too.   Before your explanation I sort of thought (although could not understand how)  the rendered fish were directly below the  boat and not the bottom vertical distance arc to each side.  Ive attached your image of the Shifted bottom detail with arrows connecting the arced image to the flat image.  Any idea how that is done?  Is this similar to rendering the 2D sonar cone to the flat screen image?  Thanks again. 

Yes it’s similar to rendering the 2d Sonar cone to the flat display screen  ...whereas the unit “paints” all the targets within the shape of the Sonar beam into a flat 1 dimensional display screen  ... in 2d we also don’t know the direction to each target - we just know how far each target is from the xducer ... and each target is within the shape of the 2d Sonar beam  ...

We can see the 2 fish targets in the left SI in this diagram are at a completely different angle from the xducer   ... but because the Sonar only knows distance and not direction - the unit “paints” those two fish targets in the SI image as side by side because the 2 fish targets are the same distance from the xducer  ...


Once we see the 2 fish targets in the dark water column of the SI image - we know those 2 fish are closer to the xducer than the value of the water depth (from my “semi-circle” description of the water column in my 1st reply above)  ...

Then we turn out attention to the fish shadow “painted” against the bottom detail to visualize how high in the water column each fish target is  ...

Rickie
« Last Edit: December 31, 2019, 10:01:21 PM by rnvinc »

Offline MikeP

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Re: Water Column rendering
« Reply #4 on: January 01, 2020, 08:10:02 AM »
Thanks for the explanation.  Amazing graphics.  Mike


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