Arches

[Bullshipper]

It has has been my loose understanding that pixels per inch of display screen height and width determined the amount of screen detail you see on your display, and not the size of the object seen in the water. So if you had a larger screen, you needed more pixels to see the same detail. I always assumed that when I saw an arch or symbol, its size reflected the strength of the return signals, and not the size of the object.

But I got this reply back from another contributor, and his logic contradicts my experience. SO WHAT'S THE DEAL? Will a fish finder see small bait fish, or 100 lb tuna without zoom on the 1000 foot scale? And will the symbol or arch always be proportionately larger than the fish I am seeing on a 1000' scale?

"On an LCD display with 240 vertical pixels, showing (for easy math calculations) 480 feet of water, each pixel would represent 2 feet of water so for a fish to light up a single pixel it would have to have an air bladder 2 feet tall. If you were to use 4X zoom, then each pixel would represent 6 inches of water, so maybe you could see a fish arch, but it'd have to be a big fish. By this same reasoning you can see that you'd never see an arch at 2000 feet unless you could bottom lock + 40 feet, or were over a whale . You should be able to see the bottom if you've got enough power, but fish arches would require some kind of band/zoom feature."

True or false???

[marti]

Bullshipper, in my whole fishfinder experience I only saw arches two times but during those two times, drifting above a wreck with cod on it, I could see big and smaller arches, at the same depht.
Not much help, I know but maybe it gets you on your way.

[auguste]

Hi

I have seen fish arches while salmon fishing

Arches depends in part on the speed you are going, the frequency of your fish finder, and the direction and speed the fish is swimming

I believe that the Lawrence web sit has an explanation about arches

[Bullshipper]

Lawaia PM'd me with a great link that explains this concept in simple terms, and some others.

This one page techical sheet is well worth the read, and I am saving it in my favorites. Definitley proved my understanding to be wrong, and the need to use zooms at depth if you want to have a chance of seeing these arches in deep water.
Really appreciate his effort to enlighten me. Owe you big time.
Jeff

http://www.eaglegps.com/support/sonar/fisharches.htm

[Bullshipper]

Correction on the link

http://www.eaglegps.com/Support/Tuto...fisharches.htm