Thread: Side image distance measurements

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


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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?


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Mark fish as a waypoint, move to it, and fish .

So we’re better off turning the water column off?


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Originally Posted by tcounty

So we’re better off turning the water column Offk

Removing the water column with HB Contour Mode does actually give a better linear representation of the bottom detail without being compressed ...

The disadvantage is losing the details in the water column that one may want to see ...

Rickie

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?


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After reading all of this I have decided that I’m too dumb to use electronics.


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Originally Posted by roachjwr

After reading all of this I have decided that I’m too dumb to use electronics.


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May have to go back to cane pole, Cork and minnow


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rnvinc , If we are in 30 ft,deep of water
(or less )and set the side image to 40 yds . we would never be off more than a jig pole length(approximately 12 ft ) would we ?

Originally Posted by eagle 1

rnvinc , If we are in 30 ft,deep of water
(or less )and set the side image to 40 yds . we would never be off more than a jig pole length(approximately 12 ft ) would we ?

Did you mean 40 ft? Instead of yards. If I put my small screen on 120 ft it compresses the pixels to where a stump looks like a dot. LOL


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