Thread: Side image distance measurements

Once we understand that the dark water column in the SI image must be interpreted separately (in our mind) from how we interpret the bottom detail in the SI image (in our mind) ...

We can see (in the diagram below) that the HB software engineers basically took the left SI image bottom detail and the right SI image bottom detail / and shifted each section of data (left SI and right SI) outward in the displayed SI image to make room in the displayed image for the water column detail ...



Rickie

The drawing explains one thing to me I had wrong. I wondered why when I went by trees that were above water and on the edge of my SI range , only show as stumps

I had in my mind the opposite of what in the picture above shows.

This is what I thought I was seeing




Sent from my iPhone using Tapatalk

Originally Posted by tcounty

The drawing explains one thing to me I had wrong. I wondered why when I went by trees that were above water and on the edge of my SI range , only show as stumps

I had in my mind the opposite of what in the picture above shows.

This is what I thought I was seeing

Unfortunately the HB diagrams on the web leave a little to be desired in fully explaining what is actually in the SI image ...

Rickie

Originally Posted by rnvinc

Once we understand that the dark water column in the SI image must be interpreted separately (in our mind) from how we interpret the bottom detail in the SI image (in our mind) ...

We can see (in the diagram below) that the HB software engineers basically took the left SI image bottom detail and the right SI image bottom detail / and shifted each section of data (left SI and right SI) outward in the displayed SI image to make room in the displayed image for the water column detail ...



Rickie

So.....if the bottom image ( directly under the boat) is shifted out so that it displays to the rh or lh side of the water column (black area) the side image measurements at the top of the display are off by the depth of the water?

Would the cursor measurement be the same as the top scale?

I noticed from some videos that the side image measurement scale at the top of the display does not change as the boat moves through various depths.






Sent from my iPad using Tapatalk

Now that we understand that the bottom detail is shifted outward left and right in the SI image to make room for the dark water column in the SI image ... we can explain what actually happens to the bottom detail in the SI image ...

Below we see two HB SI images - of the very same bottom detail ...:


*The top half is regular SI with the dark water column displayed ...
*The bottom half is SI with HB ‘s “Contour Mode” on - which basically removes the dark water column ...and correctly represents the bottom detail from directly under the boat outward to the user set SI Range selection ...

Notice the individual green marks I have drawn on specific details showing on the lake bottom in both SI images ... and how those specific bottom details are “shifted” (some outward and some inward) when the dark water column is inserted into the SI image ...

The SI Range is not different in the 2 representations - the bottom details at each edge of the screen remain the same ...

But all the other details in the bottom detail are “compressed” to make room in the displayed SI image for the dark water column section ...

This “compression” of the bottom details in the SI image (when the dark water column is displayed) - and the fact that SI Range is “slant range distance - not horizontal distance ... is why the SI Range numbers at the top of the screen should only be used as estimates of distance to targets seen on the bottom detail ...

And the “compression” of the bottom details is also why waypoints marked away from the boat in the SI image cannot be accurate ... and should be re-marked with 2d ...

There is way more going on in the SI image than simple distance from point A to point B ...

Rickie

Originally Posted by rnvinc

Now that we understand that the bottom detail is shifted outward left and right in the SI image to make room for the dark water column in the SI image ... we can explain what actually happens to the bottom detail in the SI image ...

Below we see two HB SI images - of the very same bottom detail ...:


*The top half is regular SI with the dark water column displayed ...
*The bottom half is SI with HB ‘s “Contour Mode� on - which basically removes the dark water column ...and correctly represents the bottom detail from directly under the boat outward to the user set SI Range selection ...

Notice the individual green marks I have drawn on specific details showing on the lake bottom and how those specific bottom details are “shifted� outward when the dark water column is inserted into the SI image ...

The SI Range is not different in the 2 representations - the bottom details at each edge of the screen remain the same ...

But all the other details in the bottom detail are “compressed� outward to make room in the displayed SI image for the dark water column section ...

This “compression� of the bottom details in the SI image (when the dark water column is displayed) - and the fact that SI Range is “slant range distance - not horizontal distance ... is why the SI Range numbers at the top of the screen should only be used as estimates of distance to targets seen on the bottom detail ...

And the “compression� of the bottom details is also why waypoints marked away from the boat in the SI image cannot be accurate ... and should be re-marked with 2d ...

Rickie

Thanks...makes sense now


Sent from my iPhone using Tapatalk

The deeper the water the wider your transducers cone.

Originally Posted by RustyJig

I was watching a fellow on YouTube, who seemed very knowable, give a class on side image distance measurements and how to determine where a brush pile, stump, etc. is from your boat and he demonstrated it by placing his boat in a parking lot and towing a cooler out to the side and behind his trailer. He proceeded to show how the fish finder displayed this objects distance from the transducer. Everything was clear to my understanding until he said that if the object showed 25 ft to the side of the boat and that you were in 10 ft of water then the object is physically only 15 ft to the side of the boat. He said the transducer shoots a beam to the bottom and then to the side and you must deduct the depth from the displayed distance displayed.

This would have to be taken into account if you threw a marker bouy for instance. But, he said if you use the “mark” button on the fish finder it would mark the correct spot.

Is that correct?


Sent from my iPad using Tapatalk

Sent from my SM-G960U using Crappie.com Fishing mobile app

come. Agree mind control salesmanship.

Originally Posted by Snubby

I rely on SI to show me fish, structure etc. I then turn to DI or 2D sonar to confirm the depth of what I have discovered and marked by further examination. SI is a valuable tool, but with out down sonar or down image technology it's almost rendered useless in my opinion.

Sent from my SM-G892A using Tapatalk

Sent from my SM-G960U using Crappie.com Fishing mobile app