Thread: Down Imaging vs Side imaging vs neither

Originally Posted by Stymie

I'm not talking about the shadows that are causing the horizontal black bars. I'm asking about the vertical bars on the edges of your image. Even in places without obstruction, you are in 26 feet of water and its all dark from 70-80 feet out. I noticed similarities on the image on page 2 and the images in the bass pro catalog.

1 thing we all have to keep in perspective (especially when dealing with SI images) is the properties of sonar in it's basic form...

Any image that is showing on the screen (2d/DI/SI) is "reflection echo data" of objects in the sound wave "ping" sent thru the water...

Different depths, water clarity, bottom composition, bottom contours, (even unit sensitivity settings) impact the reflection echo data that is processed and plotted into the screen image....

A hard bottom will reflect echos better than a soft bottom...making the image brighter and able to "see"out farther...
Clearer water will allow reflections better than stained water ...(waterborn particles can absorb sound waves)..
An "upsloping bottom" will reflect better than a "downsloping bottom"...
Higher sensitivity settings will allow the reflection data to be "brighter"..

I've seen images that are dark out past 30-40 feet...
I've seen images that are clear out to 70-80-90-100+ ft...

There are other sonar related rudimentary factors involved in the images shown on the screen besides just "which unit/technology/brand/setting gives the best images"....or

Why are "so-n-so's" images better than "so-n-so's"...

Rickie

Thanks Ricky.

Are you saying that Lowrance purposely pasted images from muddy water as examples for their bass pro catalog? That seems odd.

I don't hear a lot of HB folks saying to keep the SI range at 3x your depth.

I only hope to offer to the discussion sonar basic principle facts about how sonar reflections vs enviroment can cause images to be brighter/darker or clearer/fuzzier...

I have no influence or reasoning as to why Lowrance would advertise that very image...if I had to guess... I would offer that Lowrance probably expects users to "generally" see similar images in "average" conditions of water clarity/water depth/bottom hardness/bottom contour....

I keep my "SI Range" at 60-70 unless I'm in deeper than 30 ft (then the water column takes up most of the screen)..

Out past 50-60 ft ...I drop a waypoint on it and get closer to it to scan it at a more descernable distance...

Rickie

Rickie, it appears that someone is considering buying an HDS system, but has questions about the BPS catalog pictures. For me, I normally don't scan out more than 60ft, because I know what I'm looking for. Honestly, depending on the unit you have, if you are on the water, scanning 150ft each side just isn't that useful based on the scale. You might just miss some things that you'd see if it wasn't set so far.

Who gives a crap about pictures in the BPS catalog. I've never heard any HDS people complain about their unit, and I've never seen a wish list for features. The only thing that I had sticker shock on was the NMEA2000 parts. But I got over it really quick once I installed it, and know that I'll be adding more later.

I feel that real life on the water images are going to be found in the forums... From real users....

Mike still has the very best "real life" DI image I have ever seen anywhere... From any unit...In any media...

Advertising in magazines/sales clerk hype should be taken with a grain of salt...

Rickie

you da man rickie

Found this from another thread.

"Navico (Lowrance) provides the following guidelines on the limitations of side and down scan coverage:

In 20' of water using 800 kHz the maximum capability of the HDS system is 35' per side. Couple that with 20' downscan coverage and you can view a 90' window. No reason to set the side range any higher because the system is not capable with those settings. 455 kHz will increase distance at the expense of resolution per the chart. Humminbird specs are very similar.

Compared to conventional sonar, 90' is pretty good though. A 200 kHz (20 deg cone) freshwater transducer would show 1/3 of the bottom depth or roughly 7'. The 83 kHz would display double that or 14'. 90' of coverage vs. 7'...this is why bigger screens are important for side scan imaging."

I do find the HB statement odd, as that's not the case as seen from these posts. BBC Boards: Humminbird SI Screen Captures from 0' to 10'. Scrool down to the 7th post. Those kind of images get my interest when I'm fishing.
If I followed Navionics advice, I'd have my SI set at 8 feet and would miss that big school of fish.