Side Imaging. Let's Settle The Debate

[AustinV]

Ok, I've been sucked into the rabbit hole and its got me thinking...When using Side Imaging/Scan/Vu how far is it actually scanning?

Example: You're scanning 100' to the left and right, boat is sitting in 20' of water.

Are you only viewing 100' minus the 20' of water (80'), or are you viewing the full 100', but the data is compressed to squeeze in the water column?

I feel like I've been researching all over and it gets mixed opinions based on the range. Some say the range numbers displayed are slant range, some say it's purely lateral distance from the transducer and depth doesn't get accounted for. Sounds like I'm going to have to do a real on the water test.

[printman71]

Too complicated for me, but if I'm in 20 feet of water, side scanning is 2x that on either side, so 40 feet left and 40 feet right.

[Nickstanislaus]

From my under standing you would be viewing 80 feet. Hopefully someone can 100% answer that though.

[Mcjenson]

From my under standing you would be viewing 80 feet. Hopefully someone can 100% answer that though.

Thats my understanding as well. In deeper water I typically extend the range a bit.

[mikeky]

.

[bcreek]

A squared, plus B squared, equals C squared.

[AustinV]

A squared, plus B squared, equals C squared.

That can be used when determining slant range distance compared to true lateral distance. Is it truly scanning 100’ to the left/right or not?

[pabasshawk]

If you are in 20 feet of water and set to view an object that reads 100 feet out to the side then that object is actually 80 feet out to the side. You have to subtract the depth from the distance out to the side. 100 minus the 20 foot depth equals 80 feet.

[Wayne P.]

Understanding Side Imaging Range (technologicalangler.com)

[AustinV]

Understanding Side Imaging Range (technologicalangler.com)

That’s one of the things I’ve read. To me that’s saying it’s not subtracting the water column from the range because it’s purely lateral. Deeper water has more of a slant range making the object closer than the lateral range line. To me I think It’s compressing the data to fit the water column in the picture. I don’t have HB anymore, but they had a contour mode that removed the water column that I think demonstrated this. The same picture just more stretched out without the water column.

[Kdixer]

The distance is what you set it to. Meaning if you set it to 100' then that is how far it scans. But side scan starts reading at the depth. So if you are in 20' then the 1st 20' of the 100' will be black. In this example you will get returns for objects that are from 20' to 100' to each side. If you are in 60' then the 1st 60' will be black and you will get returns from 60' to 100' on each side. In either case, if you mark something 80' to the side then it is 80' to the side regardless of depth.

[basscat tyler]

The distance is what you set it to. Meaning if you set it to 100' then that is how far it scans. But side scan starts reading at the depth. So if you are in 20' then the 1st 20' of the 100' will be black. In this example you will get returns for objects that are from 20' to 100' to each side. If you are in 60' then the 1st 60' will be black and you will get returns from 60' to 100' on each side. In either case, if you mark something 80' to the side then it is 80' to the side regardless of depth.

This is how I understand it as well

[AustinV]

The distance is what you set it to. Meaning if you set it to 100' then that is how far it scans. But side scan starts reading at the depth. So if you are in 20' then the 1st 20' of the 100' will be black. In this example you will get returns for objects that are from 20' to 100' to each side. If you are in 60' then the 1st 60' will be black and you will get returns from 60' to 100' on each side. In either case, if you mark something 80' to the side then it is 80' to the side regardless of depth.

ACD89EF4-A542-4AC5-B4C2-1D08F76F0DF6.jpeg

I could agree with that, and that makes sense. But I know DV had a big part at the beginning of SI and if I understand correctly that’s not how it’s working. It’s just compressing the data more based on the water depth.

[AustinV]

060A5599-D500-423E-8899-3C9AAF6F6B7B.jpeg
this one may be easier to read

[Kdixer]

No the black strip in the center widens as depth gets deeper. As shown in you top image. If a display has "contour mode" like the bottom image, then it will distort the image some to smooth out and compensate for depth changes if contour mode is active.

[AustinV]

No the black strip in the center widens as depth gets deeper. As shown in you top image. If a display has "contour mode" like the bottom image, then it will distort the image some to smooth out and compensate for depth changes if contour mode is active.

Isn't it the opposite? The deeper the water, the wider the black area becomes. So it has to compress the actual "bottom" to fit it all in the same frame. With contour mode it shows the most true data of the actual bottom, except it can look distorted at rapid depth changes because the software isn't taking into the water column into consideration. I'm pretty sure I've seen an explanation of that from a HB Engineer on a forum.

[BigFishSteve]

As long as you believe it. HRd to believe so many have the machine but it know it’s most basic function.

[Mcjenson]

As long as you believe it. HRd to believe so many have the machine but it know it’s most basic function.

Let’s be honest though. As long as you can find structure / fish on SI and drop a waypoint on it, does it really matter if you don’t know exactly how it works?

[AustinV]

As long as you believe it. HRd to believe so many have the machine but it know it’s most basic function.

So which is the answer? I think everyone on here can probably interpret most of what they’re seeing. This is getting into a little bit more of the technical side.

[bhjr.]

Side imaging for the sides and down imaging covers the rest in the middle.